#13 Read About Dealing with Disasters
Edited by Len Phillips, updated January 2023
Sections You may go directly to the section by clicking on titles listed here.
Edited by Len Phillips, updated January 2023
Sections You may go directly to the section by clicking on titles listed here.
- Help Trees Survive Winter Injury
- Trees that Tolerate Salt Damage
- Trees that Survive Ice Storms
- Trees that Survive Hurricanes
- Trees that Survive Floods
- Trees that Survive Storm Surges
- Trees that Survive Drought
- Planting Trees during a Drought
- Heat Tolerant Trees
- Trees that Survive Landslides
- Trees that Resist Wildfires
Note: Click on green text in each section for more information and photos.
Help Trees Survive Winter Injury
In autumn, it is often necessary to provide extra attention to newly installed trees to help them over-winter and start spring in peak condition. Potential winter damage can be divided into three categories:
1. Desiccation
2. Freezing
3. Breakage
1. Desiccation
Desiccation is a significant cause of damage, particularly on evergreens when water transpires from the tree faster than it is taken up by the roots. Several environmental factors can influence desiccation. If autumn has been particularly dry or the soil is frozen, there may be insufficient moisture in the ground to supply the roots with adequate water.
Desiccation Management: Proper watering is a critical factor in winterizing trees especially those newly installed trees. Give trees a deep soaking that will supply water to the entire root system before the ground freezes. This practice is especially important for evergreens. Watering during the warm days of the winter months is also important along with mulching for erosion control and water loss prevention. A two-inch (5 cm) layer of mulch will help maintain uniform soil moisture around the roots. It also reduces the amount of alternate freezing and thawing of the soil which causes frost heaving.
Anti-desiccant compounds typically sprayed onto leaves are sold in many garden centers and supply catalogs for the purpose of slowing the rate of transpiration. However research has shown that these compounds, at the present time, degrade rapidly and are of little value for preventing desiccation.
2. Freezing
Frost heaving occurs when alternate freezing and thawing of the soil pushes small, shallow-rooted trees out of the ground. This prevents the trees from having firm contact with the soil and exposes the roots to wind desiccation. If a tree has been heaved from the ground, dig it up and reinstall the tree as soon as the soil is workable. Another alternative is to install root stabilizers at the time of planting to keep the roots firmly held to the bottom of the planting pit.
New growth that has been stimulated in early autumn by a late summer fertilization or a pruning that may not have had time to harden off sufficiently may not survive sudden temperature drops to below freezing. In these situations, ice crystals will rupture cell walls and result in dead branches and branch tips.
Freezing Management: Avoid late summer or early autumn fertilization while trees are still active, as this stimulates growth, which is easily killed by cold temperatures. A sharp temperature change between day and night may also freeze the water within the trunk of a tree causing it to explode or split open in a symptom called bark split or frost cracking. If not severe, these cracks seem to close when warmer weather arrives, although the wood fibers within the tree may not grow back together. This is sometimes called southwest injury because it is commonly found on the southwest side of trees where a warm afternoon sun creates further extremes in the day and night temperatures. In most cases trees adequately close over the cracks, with no treatment necessary.
Wrapping trunks with burlap strips or commercial tree wrap, painting the trunk white, or even shading it with a vertical board on the south side of the tree trunk may prevent bark splitting. All of these methods reflect sunlight and reduce the buildup of heat during the day, thus reducing the temperature fluctuations that cause splitting. Any wraps should be removed, at the end of the first winter season after planting, to prevent insect or moisture damage to the trunk. After the first season, most trees have adapted to their new location, so protecting the trunk is no longer necessary.
The sun can also prematurely stimulate the opening of flowers or leaf buds in the spring. Freezing night temperatures might kill the flower buds, although the leaf buds usually survive. Even with good management, injury to young growth may still occur as a result of unusual weather patterns.
Root injury may also occur in containers and planters, or balled and burlapped (B&B) stock that has been left exposed during the winter. Lethal root temperatures can start at 28°F (– 2°C) on some species. Tender trees should be placed in protected areas, sunk into the ground, grouped together, or heavily mulched to avoid low temperature injury to roots.
3. Breakage
Damage to trees in winter is usually related to breakage by the weight of snow and ice and by careless snow removal. High winds can compound the damage done to ice-covered trees. Damage may take the form of misshapen trees, broken branches, and split trunks and branches.
Breakage Management: Proper pruning at an appropriate time throughout the year is effective in reducing potential damage by ice and snow. Particularly important is the removal of any weak, narrow-angled, V-shaped crotches. Avoid late-summer pruning that stimulates new, tender growth that also reduces the supply of nutrients necessary for the tree to survive through the winter.
Snow that has collected on newly installed or weak branched shrubs should be removed with a broom. Always sweep upward with the broom to lift snow off. When the branches are frozen and brittle, avoid disturbing them until a warm day or until the ice naturally melts away.
Planning Ahead to Avoid Damage
Much of the disappointment and frustration of winter-damaged trees can be avoided by planning ahead.
Dealing with Winter Injury
After a particularly severe winter, many trees may show substantial injury such as discolored, burned evergreen needles or leaves, heaved root systems, and dead or broken branch tips and branches. The extent of winter damage can best be determined after new growth starts in the spring. At that time, prune all dead twigs or branches back to within one quarter of an inch above a live bud, or to the branch collar of the nearest live branch. Do not remove branches if scraping the outer bark reveals a green layer underneath.
If discoloration on narrow-leafed evergreen needles is not too severe, they may regain their color or develop new foliage. Broad-leaved evergreens showing leaf damage will usually produce new leaves if the leaf buds have not been too severely injured. Prune to remove badly damaged or broken branches, to shape the tree, and to stimulate new growth.
An application of fertilizer in the spring, to the soil around winter-damaged trees, accompanied by adequate watering, will usually induce new growth to compensate for winter injuries.
Special care should be given to trees injured by the cold. The dry summer months can also be particularly stressful, as the trees weakened in winter, are often unable to survive the additional stress of a summer drought.
Animal Damage
In winter, mice may chew off the bark at or below ground level and can completely girdle a tree, causing it to die. Since most of this damage takes place during winter, keep the mulch pulled away from the base of the tree and examine it frequently for the presence of mice and other animal damage. In many situations placing poison bait in rodent runways and according to directions, controls mice. Mice may also be controlled by trapping.
Deer are noted for causing damage to evergreens and fruit trees in winter. Rabbits can also chew the bark off young trees each year. Where rabbits are a common problem, a satisfactory method of preventing damage is the use of a mechanical guard around the tree trunk. Tree wraps can also be used, but must be removed in the early spring to prevent damage to the tree. Rabbit and deer repellents under various trade names are also available. Most repellents work very well if they are applied and re-applied after every precipitation event and according to the label directions.
Road Salt Damage to Trees
Road salt contains dissolved salts that injure the trees but also can change the structure of the soil, causing it to become compacted. Although the salt is applied throughout the winter, most damage occurs when trees are beginning active growth. The primary symptom of salt damage is marginal scorch on leaf edges (see Salt Tolerant and Salt Sensitive Species below).
Road Salt Damage Management: During the winter, the goal is to prevent salt from reaching the trees, and to wash it off the trees with copious amounts of water. Do not pile snow containing salt around trees or put it where runoff will flow over root zones. Where runoff is unavoidable, flush the area around the trees in early spring by applying 2" of water over a 2-3 hour period and repeat 3 days later. This will leach most of the salt from the soil. Spring rains in many locations will provide the necessary runoff to flush the salt out of the topsoil.
During the summer, incorporate large quantities of organic materials into salt damaged soil to enhance its texture and to increase its water and nutrient holding capacity. Trees that are already stressed by salt will do better if no other stresses are added to them.
Help Trees Survive Winter Injury
In autumn, it is often necessary to provide extra attention to newly installed trees to help them over-winter and start spring in peak condition. Potential winter damage can be divided into three categories:
1. Desiccation
2. Freezing
3. Breakage
1. Desiccation
Desiccation is a significant cause of damage, particularly on evergreens when water transpires from the tree faster than it is taken up by the roots. Several environmental factors can influence desiccation. If autumn has been particularly dry or the soil is frozen, there may be insufficient moisture in the ground to supply the roots with adequate water.
Desiccation Management: Proper watering is a critical factor in winterizing trees especially those newly installed trees. Give trees a deep soaking that will supply water to the entire root system before the ground freezes. This practice is especially important for evergreens. Watering during the warm days of the winter months is also important along with mulching for erosion control and water loss prevention. A two-inch (5 cm) layer of mulch will help maintain uniform soil moisture around the roots. It also reduces the amount of alternate freezing and thawing of the soil which causes frost heaving.
Anti-desiccant compounds typically sprayed onto leaves are sold in many garden centers and supply catalogs for the purpose of slowing the rate of transpiration. However research has shown that these compounds, at the present time, degrade rapidly and are of little value for preventing desiccation.
2. Freezing
Frost heaving occurs when alternate freezing and thawing of the soil pushes small, shallow-rooted trees out of the ground. This prevents the trees from having firm contact with the soil and exposes the roots to wind desiccation. If a tree has been heaved from the ground, dig it up and reinstall the tree as soon as the soil is workable. Another alternative is to install root stabilizers at the time of planting to keep the roots firmly held to the bottom of the planting pit.
New growth that has been stimulated in early autumn by a late summer fertilization or a pruning that may not have had time to harden off sufficiently may not survive sudden temperature drops to below freezing. In these situations, ice crystals will rupture cell walls and result in dead branches and branch tips.
Freezing Management: Avoid late summer or early autumn fertilization while trees are still active, as this stimulates growth, which is easily killed by cold temperatures. A sharp temperature change between day and night may also freeze the water within the trunk of a tree causing it to explode or split open in a symptom called bark split or frost cracking. If not severe, these cracks seem to close when warmer weather arrives, although the wood fibers within the tree may not grow back together. This is sometimes called southwest injury because it is commonly found on the southwest side of trees where a warm afternoon sun creates further extremes in the day and night temperatures. In most cases trees adequately close over the cracks, with no treatment necessary.
Wrapping trunks with burlap strips or commercial tree wrap, painting the trunk white, or even shading it with a vertical board on the south side of the tree trunk may prevent bark splitting. All of these methods reflect sunlight and reduce the buildup of heat during the day, thus reducing the temperature fluctuations that cause splitting. Any wraps should be removed, at the end of the first winter season after planting, to prevent insect or moisture damage to the trunk. After the first season, most trees have adapted to their new location, so protecting the trunk is no longer necessary.
The sun can also prematurely stimulate the opening of flowers or leaf buds in the spring. Freezing night temperatures might kill the flower buds, although the leaf buds usually survive. Even with good management, injury to young growth may still occur as a result of unusual weather patterns.
Root injury may also occur in containers and planters, or balled and burlapped (B&B) stock that has been left exposed during the winter. Lethal root temperatures can start at 28°F (– 2°C) on some species. Tender trees should be placed in protected areas, sunk into the ground, grouped together, or heavily mulched to avoid low temperature injury to roots.
3. Breakage
Damage to trees in winter is usually related to breakage by the weight of snow and ice and by careless snow removal. High winds can compound the damage done to ice-covered trees. Damage may take the form of misshapen trees, broken branches, and split trunks and branches.
Breakage Management: Proper pruning at an appropriate time throughout the year is effective in reducing potential damage by ice and snow. Particularly important is the removal of any weak, narrow-angled, V-shaped crotches. Avoid late-summer pruning that stimulates new, tender growth that also reduces the supply of nutrients necessary for the tree to survive through the winter.
Snow that has collected on newly installed or weak branched shrubs should be removed with a broom. Always sweep upward with the broom to lift snow off. When the branches are frozen and brittle, avoid disturbing them until a warm day or until the ice naturally melts away.
Planning Ahead to Avoid Damage
Much of the disappointment and frustration of winter-damaged trees can be avoided by planning ahead.
- Select Hardy Trees – Install trees that are native, cultivars of natives, or are known to be winter hardy in your area.
- Select an Appropriate Site – When installing trees that are known to be easily injured, select a location where they will be protected from prevailing winds and intense winter sun. These protected exposures will also delay spring growth, thus preventing late spring frost injury to new flower growth.
- Avoid Low Spots and Roof Overhangs – Avoid sites that are likely to experience rapid fluctuations in temperature, heavy snow, and ice loads.
- Promote Healthy Trees – Do not plant trees that are diseased or deficient in nutrients.
- Treating Winter Injury – Many trees have protective mechanisms such as shedding leaves, positioning their leaves flat against their stems, rolling their leaves downward or the margins inward; and wilted-looking leaves. The red, purple, bronze, and brown winter color of some evergreens should not be confused with winter injury.
Dealing with Winter Injury
After a particularly severe winter, many trees may show substantial injury such as discolored, burned evergreen needles or leaves, heaved root systems, and dead or broken branch tips and branches. The extent of winter damage can best be determined after new growth starts in the spring. At that time, prune all dead twigs or branches back to within one quarter of an inch above a live bud, or to the branch collar of the nearest live branch. Do not remove branches if scraping the outer bark reveals a green layer underneath.
If discoloration on narrow-leafed evergreen needles is not too severe, they may regain their color or develop new foliage. Broad-leaved evergreens showing leaf damage will usually produce new leaves if the leaf buds have not been too severely injured. Prune to remove badly damaged or broken branches, to shape the tree, and to stimulate new growth.
An application of fertilizer in the spring, to the soil around winter-damaged trees, accompanied by adequate watering, will usually induce new growth to compensate for winter injuries.
Special care should be given to trees injured by the cold. The dry summer months can also be particularly stressful, as the trees weakened in winter, are often unable to survive the additional stress of a summer drought.
Animal Damage
In winter, mice may chew off the bark at or below ground level and can completely girdle a tree, causing it to die. Since most of this damage takes place during winter, keep the mulch pulled away from the base of the tree and examine it frequently for the presence of mice and other animal damage. In many situations placing poison bait in rodent runways and according to directions, controls mice. Mice may also be controlled by trapping.
Deer are noted for causing damage to evergreens and fruit trees in winter. Rabbits can also chew the bark off young trees each year. Where rabbits are a common problem, a satisfactory method of preventing damage is the use of a mechanical guard around the tree trunk. Tree wraps can also be used, but must be removed in the early spring to prevent damage to the tree. Rabbit and deer repellents under various trade names are also available. Most repellents work very well if they are applied and re-applied after every precipitation event and according to the label directions.
Road Salt Damage to Trees
Road salt contains dissolved salts that injure the trees but also can change the structure of the soil, causing it to become compacted. Although the salt is applied throughout the winter, most damage occurs when trees are beginning active growth. The primary symptom of salt damage is marginal scorch on leaf edges (see Salt Tolerant and Salt Sensitive Species below).
Road Salt Damage Management: During the winter, the goal is to prevent salt from reaching the trees, and to wash it off the trees with copious amounts of water. Do not pile snow containing salt around trees or put it where runoff will flow over root zones. Where runoff is unavoidable, flush the area around the trees in early spring by applying 2" of water over a 2-3 hour period and repeat 3 days later. This will leach most of the salt from the soil. Spring rains in many locations will provide the necessary runoff to flush the salt out of the topsoil.
During the summer, incorporate large quantities of organic materials into salt damaged soil to enhance its texture and to increase its water and nutrient holding capacity. Trees that are already stressed by salt will do better if no other stresses are added to them.
Trees That Tolerate Salt Damage
Many trees can be disfigured and killed by salt (sodium chloride), although other salts can cause some damage as well. The worst sodium chloride damage occurs to sensitive species installed near heavily salted roads. Looking for "witch's brooms" on deciduous trees and yellow, brown, or fallen needles on evergreens can aid in identifying winter salt damage.
Foliar damage from salt spray normally occurs on the windward side of the tree, but in severe cases the whole tree may be affected. Arborvitae, pine, and hemlock are most susceptible, but winter browning can affect all evergreens. New transplants or trees with succulent, late season growth are also sensitive.
Trees Tolerant to Salt Spray
Scientific name Common name
Acer campestre Hedge maple
Acer platanoides Norway maple
Acer pseudoplatanus Sycamore maple
Acer saccharinum Silver maple
Aesculus spp. Buckeye
Aesculus hippocastanum Horsechestnut
Ailanthus altissima Tree of heaven, Ailanthus
Amelanchier spp. Shadblow, serviceberry
Asimina triloba Pawpaw
Betula spp. Birch
Carya spp. Hickory/pecan
Casuarina equisetifolia Australian pine
Catalpa spp. Catalpa
Cercidiphyllum japonicum Katsura tree
Chionanthus virginicus White fringe tree
Cladrastis lutea American yellowwood
Clusia rosea Pitch apple
Cocos nucifera Coconut palm
Conocarpus erecta Buttonwood
Cornus florida Flowering dogwood
Cupaniopsis anacardioides Carrotwood
Diospyros virginiana Common persimmon
Elaeagnus angustifolia Russian olive
Fraxinus spp. Ash
Fraxinus quadrangulata Blue ash
Ginkgo biloba Ginkgo, maidenhair tree
Gleditsia triacanthos Common honey locust
Gymnocladus dioicus Kentucky coffeetree
Ilex opaca American holly
Jacaranda mimosaefolia Jacaranda
Juglans spp. Walnut/butternut
Juniperus spp. Juniper
Koelreuteria paniculata Goldenraintree
Laburnum x watereri Goldenchain tree
Larix decidua European larch
Liquidambar styraciflua Sweetgum
Maclura pomifera Osage orange
Magnolia spp. Magnolia
Malus spp. Apple, crabapple
Morus spp. Mulberry
Nyssa sylvatica Tupelo, blackgum, sourgum
Ostrya virginiana Hophornbeam, ironwood
Oxydendrum arboreum Sourwood
Paulownia tomentosa Paulownia
Persea borbonia Redbay
Phellodendron spp. Corktree
Picea glauca White spruce
Picea pungens Colorado spruce
Pinus nigra Austrian pine
Platanus spp. Plane tree/ sycamore
Populus spp. Poplar
Prunus spp. Cherry/plum
Pseudolarix amabilis Golden larch
Pseudotsuga menziesii Douglasfir
Pyrus calleryana Callery pear
Quercus alba White oak
Quercus bicolor Swamp white oak
Quercus imbricaria Shingle oak
Quercus macrocarpa Bur oak
Quercus palustris Pin oak
Quercus phellos Willow oak
Quercus robur English oak
Quercus rubra Red oak
Quercus velutina Black oak
Quercus virginiana Live oak
Rhamnus cathartica Common buckthorn
Robinia spp. Locust
Sabal palmetto Cabbage palm
Salix spp. Willow
Sassafras albidum Sassafras
Sophora japonica Japanese pagodatree
Sorbus spp. Mountain ash
Syringa pekinensis Pekin lilac
Taxodium spp. Cypress
Taxus spp. Yew
Ulmus spp. Elm
Ulmus pumila Siberian elm
Trees Tolerant to Salt in Soil
Scientific name Common name
Acer campestre Hedge maple
Acer platanoides Norway maple
Acer saccharinum Silver maple
Aesculus hippocastanum Horsechestnut
Ailanthus altissima Tree of heaven, Ailanthus
Clusia rosea Pitch apple
Cocos nucifera Coconut palm
Conocarpus erecta Buttonwood
Cornus florida Flowering dogwood
Crataegus spp. Hawthorn
Cupaniopsis anacardioides Carrotwood
Elaeagnus angustifolia Russian olive
Fraxinus spp. Ash
Ginkgo biloba Ginkgo, maidenhair tree
Gleditsia triacanthos Common honey locust
Juglans spp. Walnut/butternut
Juniperus spp. Juniper
Koelreuteria paniculata Goldenraintree
Laburnum x watereri Goldenchain tree
Larix decidua European larch
Morus spp. Mulberry
Persea borbonia Redbay
Picea pungens Colorado spruce
Pinus nigra Austrian pine
Pinus thunbergiana Japanese black pine
Populus spp. Poplar
Quercus alba White oak
Quercus robur English oak
Quercus rubra Red oak
Quercus virginiana Live oak
Rhamnus cathartica Common buckthorn
Robinia spp. Locust
Sabal palmetto Cabbage palm
Salix spp. Willow
Syringa pekinensis Pekin lilac
Taxodium spp. Cypress
Ulmus pumila Siberian elm
Many trees can be disfigured and killed by salt (sodium chloride), although other salts can cause some damage as well. The worst sodium chloride damage occurs to sensitive species installed near heavily salted roads. Looking for "witch's brooms" on deciduous trees and yellow, brown, or fallen needles on evergreens can aid in identifying winter salt damage.
Foliar damage from salt spray normally occurs on the windward side of the tree, but in severe cases the whole tree may be affected. Arborvitae, pine, and hemlock are most susceptible, but winter browning can affect all evergreens. New transplants or trees with succulent, late season growth are also sensitive.
Trees Tolerant to Salt Spray
Scientific name Common name
Acer campestre Hedge maple
Acer platanoides Norway maple
Acer pseudoplatanus Sycamore maple
Acer saccharinum Silver maple
Aesculus spp. Buckeye
Aesculus hippocastanum Horsechestnut
Ailanthus altissima Tree of heaven, Ailanthus
Amelanchier spp. Shadblow, serviceberry
Asimina triloba Pawpaw
Betula spp. Birch
Carya spp. Hickory/pecan
Casuarina equisetifolia Australian pine
Catalpa spp. Catalpa
Cercidiphyllum japonicum Katsura tree
Chionanthus virginicus White fringe tree
Cladrastis lutea American yellowwood
Clusia rosea Pitch apple
Cocos nucifera Coconut palm
Conocarpus erecta Buttonwood
Cornus florida Flowering dogwood
Cupaniopsis anacardioides Carrotwood
Diospyros virginiana Common persimmon
Elaeagnus angustifolia Russian olive
Fraxinus spp. Ash
Fraxinus quadrangulata Blue ash
Ginkgo biloba Ginkgo, maidenhair tree
Gleditsia triacanthos Common honey locust
Gymnocladus dioicus Kentucky coffeetree
Ilex opaca American holly
Jacaranda mimosaefolia Jacaranda
Juglans spp. Walnut/butternut
Juniperus spp. Juniper
Koelreuteria paniculata Goldenraintree
Laburnum x watereri Goldenchain tree
Larix decidua European larch
Liquidambar styraciflua Sweetgum
Maclura pomifera Osage orange
Magnolia spp. Magnolia
Malus spp. Apple, crabapple
Morus spp. Mulberry
Nyssa sylvatica Tupelo, blackgum, sourgum
Ostrya virginiana Hophornbeam, ironwood
Oxydendrum arboreum Sourwood
Paulownia tomentosa Paulownia
Persea borbonia Redbay
Phellodendron spp. Corktree
Picea glauca White spruce
Picea pungens Colorado spruce
Pinus nigra Austrian pine
Platanus spp. Plane tree/ sycamore
Populus spp. Poplar
Prunus spp. Cherry/plum
Pseudolarix amabilis Golden larch
Pseudotsuga menziesii Douglasfir
Pyrus calleryana Callery pear
Quercus alba White oak
Quercus bicolor Swamp white oak
Quercus imbricaria Shingle oak
Quercus macrocarpa Bur oak
Quercus palustris Pin oak
Quercus phellos Willow oak
Quercus robur English oak
Quercus rubra Red oak
Quercus velutina Black oak
Quercus virginiana Live oak
Rhamnus cathartica Common buckthorn
Robinia spp. Locust
Sabal palmetto Cabbage palm
Salix spp. Willow
Sassafras albidum Sassafras
Sophora japonica Japanese pagodatree
Sorbus spp. Mountain ash
Syringa pekinensis Pekin lilac
Taxodium spp. Cypress
Taxus spp. Yew
Ulmus spp. Elm
Ulmus pumila Siberian elm
Trees Tolerant to Salt in Soil
Scientific name Common name
Acer campestre Hedge maple
Acer platanoides Norway maple
Acer saccharinum Silver maple
Aesculus hippocastanum Horsechestnut
Ailanthus altissima Tree of heaven, Ailanthus
Clusia rosea Pitch apple
Cocos nucifera Coconut palm
Conocarpus erecta Buttonwood
Cornus florida Flowering dogwood
Crataegus spp. Hawthorn
Cupaniopsis anacardioides Carrotwood
Elaeagnus angustifolia Russian olive
Fraxinus spp. Ash
Ginkgo biloba Ginkgo, maidenhair tree
Gleditsia triacanthos Common honey locust
Juglans spp. Walnut/butternut
Juniperus spp. Juniper
Koelreuteria paniculata Goldenraintree
Laburnum x watereri Goldenchain tree
Larix decidua European larch
Morus spp. Mulberry
Persea borbonia Redbay
Picea pungens Colorado spruce
Pinus nigra Austrian pine
Pinus thunbergiana Japanese black pine
Populus spp. Poplar
Quercus alba White oak
Quercus robur English oak
Quercus rubra Red oak
Quercus virginiana Live oak
Rhamnus cathartica Common buckthorn
Robinia spp. Locust
Sabal palmetto Cabbage palm
Salix spp. Willow
Syringa pekinensis Pekin lilac
Taxodium spp. Cypress
Ulmus pumila Siberian elm
Trees that Survive Ice Storms
Severe ice storms occur every year in the United States and Canada, particularly in the Midwestern and Eastern regions of the United States. These storms are responsible for deaths and injuries to people and result in losses of millions of dollars. Damage to electric distribution systems, blocked roadways, and property damage from fallen trees and branches pose safety concerns and disrupt normal community functions.
Storm Development
Ice storm damage occurs when freezing rain accumulates on surfaces like tree branches and electrical wires. The U.S. National Weather Service defines ice storms as the accumulation of at least ¼ in. (0.625 cm) of ice on exposed surfaces. Typically ice storms can develop when a moist winter warm front passes over a colder layer of surface air. Rain falls from a warmer layer (above the freezing point of 32ºF (0ºC) through layers of cooler air without freezing but becomes super-cooled. Then the ice accumulates when this super-cooled rain freezes on contact with surfaces that are at or below the freezing point.
The severity of damage increases with greater accumulations of ice. Accumulations between ¼ and ½ inch (0.625 and 1.25 cm) can cause small and weak branches to break and ½ inch (1.25 cm) or greater of ice can cause large branches to break.
Most ice storms last only a few hours, but some storms may occur over several days depending on the weather patterns. Strong winds substantially increase the potential for damage from ice accumulation. Ice storms occur in the United States from October through April. Ninety percent occur between December and March with most occurring in January.
Monetary losses to forests, individual trees, utility lines, agriculture, commerce, and property can be extensive after an ice storm. As an example, losses from a 1998 ice storm that covered the northeastern United States and southeastern Canada were estimated at US$6.2 billion with less than one-half of this amount insured. Other impacts included more than four million people without power and more than 40 deaths attributed to this storm.
Ice Storm Damage Categories
Ice storm damage to trees can be placed into five categories:
1. broken branches,
2. trunk bending,
3. splitting of main or co-dominant stems,
4. complete trunk failure,
5. tipping or up-rooting
Damage to trees
The damage to trees from ice storms depends on many factors:
Branch breaking is the most common form of ice-induced damage and generally is the most easily repaired. Trees that have been uprooted, sustained trunk failure or have broken branches over more than 50% of the crown should be pruned or removed immediately.
The remarkable resilience of trees poses a problem for municipal arborists and property owners as they struggle with the decision to repair or remove trees damaged by ice storms. Removing a tree when it can be repaired with an equal investment of time and resources represents a net loss in benefits to the community and property owners. Conversely, failure to remove a tree that cannot be restored to a safe and sound condition increases both the likelihood of future failure with potential property damage and personal injury.
The long-term impact on tree survivability and structural integrity is related to the total number of branches lost relative to the entire canopy and the size of the branches lost. Generally, damaged trees can be managed if less than 50% of the branches are affected and the loss is predominantly to lateral branches or the tips of scaffold branches. Corrective pruning cuts should follow natural pruning practices with the intent to promote balanced crown development.
The accumulation of ice can often produce damage to a branch that is not immediately evident. This hidden damage manifests itself in the formation of cracks that run parallel to the branch and originate near or at the point of attachment. These branches must be removed as soon as they are identified as they possess a high potential to fail.
Excessive ice loads can also induce branch splitting at the point of attachment. Repair typically involves pruning the ends of one or more of the affected branches to reduce the load and the installation of cables and braces to provide additional mechanical support. Branches that have structural support systems installed in them must be monitored on an annual basis. In some cases, particularly on large, older trees, if the extent of the split is too severe, the affected branch must be removed.
Trees that bend under the load of accumulated ice will, in most cases, return to their pre-storm form, once the ice has melted. The fact that the tree did not break under the tremendous load suggests good structural integrity.
Resistance to Damage
Trees that have characteristics that impart resistance to ice storm damage include:
Reduce Tree Damage
Installing a diverse urban forest that includes trees resistant to ice storms and performing regular tree maintenance to avoid or remove structural weaknesses, will reduce damage caused by severe ice storms.
Depending upon the level of damage, forest trees such as pin cherry (Prunus), quaking aspen (Populus), jack pine (Pinus), and sugar maple (Acer) will likely die within a few years if canopy damage exceeds 50 percent. In contrast, tree species such as pitch pine (Pinus) and American beech (Fagus) have an excellent sprouting ability with the potential to develop new branches and survive after an ice storm.
Urban Forest Management
Proper tree placement and pruning on a regular cycle will reduce the potential for ice storm damage. Trees located near homes and other structures should be evaluated regularly for the risk of tree failure. Trees that receive structural pruning from a young age should be more resistant to ice storms.
Regular utility right-of-way inspection is important to minimize outages. Public education about the need to manage trees near utility lines should be encouraged, because it is in the best interests of utility companies, communities, and electricity consumers.
Ice storm frequency and severity within the eastern United States necessitates the incorporation of ice storm information into the urban forestry planning process. While we cannot stop ice storms from occurring, we can take steps to reduce the impact of damage to urban forests and the interface between forests, buildings, and infrastructure.
Severe ice storms occur every year in the United States and Canada, particularly in the Midwestern and Eastern regions of the United States. These storms are responsible for deaths and injuries to people and result in losses of millions of dollars. Damage to electric distribution systems, blocked roadways, and property damage from fallen trees and branches pose safety concerns and disrupt normal community functions.
Storm Development
Ice storm damage occurs when freezing rain accumulates on surfaces like tree branches and electrical wires. The U.S. National Weather Service defines ice storms as the accumulation of at least ¼ in. (0.625 cm) of ice on exposed surfaces. Typically ice storms can develop when a moist winter warm front passes over a colder layer of surface air. Rain falls from a warmer layer (above the freezing point of 32ºF (0ºC) through layers of cooler air without freezing but becomes super-cooled. Then the ice accumulates when this super-cooled rain freezes on contact with surfaces that are at or below the freezing point.
The severity of damage increases with greater accumulations of ice. Accumulations between ¼ and ½ inch (0.625 and 1.25 cm) can cause small and weak branches to break and ½ inch (1.25 cm) or greater of ice can cause large branches to break.
Most ice storms last only a few hours, but some storms may occur over several days depending on the weather patterns. Strong winds substantially increase the potential for damage from ice accumulation. Ice storms occur in the United States from October through April. Ninety percent occur between December and March with most occurring in January.
Monetary losses to forests, individual trees, utility lines, agriculture, commerce, and property can be extensive after an ice storm. As an example, losses from a 1998 ice storm that covered the northeastern United States and southeastern Canada were estimated at US$6.2 billion with less than one-half of this amount insured. Other impacts included more than four million people without power and more than 40 deaths attributed to this storm.
Ice Storm Damage Categories
Ice storm damage to trees can be placed into five categories:
1. broken branches,
2. trunk bending,
3. splitting of main or co-dominant stems,
4. complete trunk failure,
5. tipping or up-rooting
Damage to trees
The damage to trees from ice storms depends on many factors:
- amount and duration of accumulating ice,
- exposure to wind,
- wood strength,
- weak branch forks indicated by a narrow branch angle and included bark,
- decaying or dead branches,
- tree height and diameter,
- increased surface area of lateral branches,
- broad and unbalanced crowns,
- shallow, restricted, and unbalanced root systems,
- susceptibility to tree pathogens
Branch breaking is the most common form of ice-induced damage and generally is the most easily repaired. Trees that have been uprooted, sustained trunk failure or have broken branches over more than 50% of the crown should be pruned or removed immediately.
The remarkable resilience of trees poses a problem for municipal arborists and property owners as they struggle with the decision to repair or remove trees damaged by ice storms. Removing a tree when it can be repaired with an equal investment of time and resources represents a net loss in benefits to the community and property owners. Conversely, failure to remove a tree that cannot be restored to a safe and sound condition increases both the likelihood of future failure with potential property damage and personal injury.
The long-term impact on tree survivability and structural integrity is related to the total number of branches lost relative to the entire canopy and the size of the branches lost. Generally, damaged trees can be managed if less than 50% of the branches are affected and the loss is predominantly to lateral branches or the tips of scaffold branches. Corrective pruning cuts should follow natural pruning practices with the intent to promote balanced crown development.
The accumulation of ice can often produce damage to a branch that is not immediately evident. This hidden damage manifests itself in the formation of cracks that run parallel to the branch and originate near or at the point of attachment. These branches must be removed as soon as they are identified as they possess a high potential to fail.
Excessive ice loads can also induce branch splitting at the point of attachment. Repair typically involves pruning the ends of one or more of the affected branches to reduce the load and the installation of cables and braces to provide additional mechanical support. Branches that have structural support systems installed in them must be monitored on an annual basis. In some cases, particularly on large, older trees, if the extent of the split is too severe, the affected branch must be removed.
Trees that bend under the load of accumulated ice will, in most cases, return to their pre-storm form, once the ice has melted. The fact that the tree did not break under the tremendous load suggests good structural integrity.
Resistance to Damage
Trees that have characteristics that impart resistance to ice storm damage include:
- Juvenile and mature trees that have conical branching patterns, strong branch attachments, flexible branches, and low surface area of lateral branches are generally resistant to ice storms. Species such as sweet gum (Liquidambar) and tulip poplar (Liriodendron) have a conical growth habit when young but develop an open crown growth habit later in life. As a result, these species are more resistant to breakage when young.
- Tree species with strong branch angles and attachments have greater resistance to breakage than those with weak branch junctures indicated by included bark. 'Bradford' pear (Pyrus) branches often break during ice storms where there is included bark in branch junctures. In contrast, the 'Aristocrat' cultivar of the same pear species (Pyrus calleryana) has few branches with included bark and sustains less damage during ice storms.
- Trees with coarse branching patterns and, as a consequence, lateral branches with reduced surface area, such as Kentucky coffee tree (Gymnocladus), black walnut (Juglans), and ginkgo (Ginkgo), accumulate less ice and typically have little breakage from ice storms.
- Forest understory tree species, such as hophornbeam (Ostrya), blue beech (Carpinus), amur maple (Acer), and serviceberry (Amelanchier), are relatively resistant to ice storm damage. Younger trees and those with greater flexibility or elasticity of branches have greater resistance. American elm (Ulmus) expresses resistance as a member of the lower canopy, yet becomes more susceptible to damage as an upper canopy tree.
- Trees that develop a greater taper of the main trunk or with buttresses can support more mass and tend to have greater resistance to failure than spindly trees with less taper.
- Seed source of trees also influences ice storm resistance. A tree species indigenous to areas subject to severe ice storms seem to have greater resistance than those not from such areas. For example, loblolly pine (Pinus) trees from more northern latitudes experience less ice storm damage than those from more southerly locations when grown in the same exposure.
- Forest edge trees tend to have large, unbalanced crowns with longer, lower and more branches on the open side, which makes them susceptible to damage. Interior forest trees, the crowns of which must compete for light, have small crowns with shorter main branches and fewer lower branches and typically show less damage than edge trees.
- Trees on slopes, and especially those facing north and east, tend to have greater ice storm damage because of imbalances in the crowns and roots.
- Vine growth on forest trees can increase susceptibility to ice storm damage by increasing the surface area that accumulates ice. Also, some vines will twist around a branch and weaken it, making it more susceptible to winter damage.
- Species with shallow root systems, such as red oak (Quercus), are more prone to tipping during ice storms than deep-rooted species, such as white oak and bur oak, especially if the ground is unfrozen and the soil is saturated.
- Trees such as birch (Betula), bald cypress (Taxodium), and arborvitae (Thuja) will naturally bend with the weight of ice and usually return to their natural form after the ice melts.
Reduce Tree Damage
Installing a diverse urban forest that includes trees resistant to ice storms and performing regular tree maintenance to avoid or remove structural weaknesses, will reduce damage caused by severe ice storms.
Depending upon the level of damage, forest trees such as pin cherry (Prunus), quaking aspen (Populus), jack pine (Pinus), and sugar maple (Acer) will likely die within a few years if canopy damage exceeds 50 percent. In contrast, tree species such as pitch pine (Pinus) and American beech (Fagus) have an excellent sprouting ability with the potential to develop new branches and survive after an ice storm.
Urban Forest Management
Proper tree placement and pruning on a regular cycle will reduce the potential for ice storm damage. Trees located near homes and other structures should be evaluated regularly for the risk of tree failure. Trees that receive structural pruning from a young age should be more resistant to ice storms.
Regular utility right-of-way inspection is important to minimize outages. Public education about the need to manage trees near utility lines should be encouraged, because it is in the best interests of utility companies, communities, and electricity consumers.
Ice storm frequency and severity within the eastern United States necessitates the incorporation of ice storm information into the urban forestry planning process. While we cannot stop ice storms from occurring, we can take steps to reduce the impact of damage to urban forests and the interface between forests, buildings, and infrastructure.
Trees that Survive Hurricanes
Arborists and landscape architects should be setting the standards for better planting locations, limits for “fall zones” or targets of failure risk, hurricane resistant species selections, and recommendations for tree sizes, structural supports, annual or seasonal maintenance routines, and storm preparation pruning specifications. In addition, arborists and landscape architects should also recognize the importance of preserving groves of trees, urban forest buffers, and the tree canopy within public parks and community open spaces. Arborists and landscape architects might even address the community post-storm clearing and clean up procedures, as well as disposal, recycling, and cost issues with the objective of strengthening the urban forest to better protect human life and property. This information will help arborists and landscape architects during the selection and growing of the right tree at the right place for the right reasons.
Recommended Trees for the Southeastern United States
Researchers at the University of Florida have found the following trees have survived against hurricane force winds in southeastern portions of the US. The recommended tree and shrub species listed below are divided into the Southeastern Coastal Plain region from Texas to coastal North Carolina (including USDA hardiness zones 8 and 9) and Tropical and Subtropical regions such as southern Florida (USDA hardiness zones 10 and 11). Some of these trees may be hurricane resistant in cooler climates as well.
Southeastern Coastal Plain Region
Highest wind tolerance
Butia capitata, pindo or jelly palm
Carya floridana, Florida scrub hickory
Cornus florida, dogwood
Ilex cassine, dahoon holly
Ilex glabra, inkberry
Ilex opaca, American holly
Ilex vomitoria, yaupon holly
Lagerstroemia indica, crape myrtle
Magnolia grandiflora, southern magnolia
Quercus geminata, sand live oak
Quercus laevis, turkey oak
Quercus myrtiflora, myrtle oak
Quercus virginiana, live oak
Phoenix canariensis, Canary Island date palm
Phoenix dactylifera, date palm
Podocarpus spp, podocarpus
Sabal palmetto, cabbage, sabal palm
Taxodium distichum, baldcypress
Taxodium ascendens, pondcypress
Vaccinium arboreum, sparkleberry
Medium to high wind tolerance
Acer saccharum, Florida sugar maple
Acer palmatum, Japanese maple
Betula nigra, river birch
Carpinus caroliniana, ironwood
Carya glabra, pignut hickory
Carya tomentosa, mockemut hickory
Celtis occidentalis, Common hackberry
Cercis canadensis, red bud
Chionanthus virginicus, fringe tree
Diospyros virginiana, common persimmon
Fraxinus americana, white ash
Liquidambar styraciflua, sweetgum
Magnolia virginiana, sweetbay magnolia
Magnolia x soulangiana, saucer magnolia
Nyssa aquatica, water tupelo
Nyssa sylvatica, black tupelo
Ostrya virginiana, American hophornbeam
Prunus angustifolia, chickasaw plum
Quercus michauxii, swamp chestnut
Quercus shumardii, Shumard oak
Quercus stellata, post oak
Ulmus alata, winged elm
Tropical and Subtropical Region
Highest wind tolerance
Bursera simaruba, gumbo limbo
Butia capitata, pindo or jelly palm
Carya floridana, Florida scrub hickory
Conocarpus erectus, buttonwood
Chrysobalanus icaco, cocoplum
Coccothrinax argentata, Florida silver palm
Cordia sebestena, geiger tree
Dypsis lutescens, areca palm
Eugenia axillaris, white stopper
Eugenia confusa, redberry
Eugenia foetida, boxleaf stopper
Guaiacum sanctum, lignum vitae
Hyophorbe lagenicaulis, bottle palm
Hyophorbe verschaffeltii, spindle palm
Ilex cassine, dahoon holly
Krugiodendrum ferreum, ironwood
Lagerstroemia indica, crape myrtle
Latania loddigesii, blue latan palm
Livistona chinensis, Chinese fan palm
Magnolia grandiflora, southern magnolia
Phoenix canariensis, Canary Island date palm
Phoenix dactylifera, date palm
Phoenix reclinata, Senegal date palm
Phoenix roebelenii, pygmy date palm
Podocarpus spp, podocarpus
Ptychoesperma elegans, Alexander Sabal palmetto, cabbage, sabal palm
Quercus virginiana, live oak
Quercus geminata, sand live oak
Taxodium ascendens, pondcypress
Taxodium distichum, baldcypress
Thrinax morrisii, key thatch palm
Thrinax radiata, Florida thatch palm
Veitchia merrillii, Manila palm
Medium to High wind tolerance
Annona glabra, pond apple
Calophyllum calaba, Brazilian beautyleaf
Caryota mitis, fishtail palm
Chrysophyllum oliviforme, satinleaf
Coccoloba uvifera, sea grape
Coccoloba diversifolia, pigeon plum
Cocos nucifera, coconut palm
Dypsis decaryi, triangle palm
Liquidambar styraciflua, sweetgum
Litchi chinensis, lychee
Lysiloma latsiliqua, wild tamarind
Magnolia virginiana, sweetbay magnolia
Nyssa sylvatica, black tupelo
Roystonea elata, royal palm
Sideroxylon foetidissimum, mastic
Simarouba glauca, paradise tree
Swietenia mahagoni, mahogany
Note: Other trees are considered to have low to medium wind resistance.
Tree Selection
Other factors the arborist and landscape architect should consider includes removing over-mature and tree species at risk that have demonstrated poor survival in hurricanes. Then, during the reinstalling process, replace these tree species at risk with high-quality trees from the lists above.
- Small trees need at least 10 feet by 10 feet (3x3x1m) of good soil area.
- Medium trees need 20 feet by 20 feet (6x6x1m) of area.
- Large trees need at least 30 feet by 30 feet (9x9x1m) of area.
Other Considerations
Arborists and landscape architects should be setting the standards for better planting locations, limits for “fall zones” or targets of failure risk, hurricane resistant species selections, and recommendations for tree sizes, structural supports, annual or seasonal maintenance routines, and storm preparation pruning specifications. In addition, arborists and landscape architects should also recognize the importance of preserving groves of trees, urban forest buffers, and the tree canopy within public parks and community open spaces. Arborists and landscape architects might even address the community post-storm clearing and clean up procedures, as well as disposal, recycling, and cost issues with the objective of strengthening the urban forest to better protect human life and property. This information will help arborists and landscape architects during the selection and growing of the right tree at the right place for the right reasons.
Recommended Trees for the Southeastern United States
Researchers at the University of Florida have found the following trees have survived against hurricane force winds in southeastern portions of the US. The recommended tree and shrub species listed below are divided into the Southeastern Coastal Plain region from Texas to coastal North Carolina (including USDA hardiness zones 8 and 9) and Tropical and Subtropical regions such as southern Florida (USDA hardiness zones 10 and 11). Some of these trees may be hurricane resistant in cooler climates as well.
Southeastern Coastal Plain Region
Highest wind tolerance
Butia capitata, pindo or jelly palm
Carya floridana, Florida scrub hickory
Cornus florida, dogwood
Ilex cassine, dahoon holly
Ilex glabra, inkberry
Ilex opaca, American holly
Ilex vomitoria, yaupon holly
Lagerstroemia indica, crape myrtle
Magnolia grandiflora, southern magnolia
Quercus geminata, sand live oak
Quercus laevis, turkey oak
Quercus myrtiflora, myrtle oak
Quercus virginiana, live oak
Phoenix canariensis, Canary Island date palm
Phoenix dactylifera, date palm
Podocarpus spp, podocarpus
Sabal palmetto, cabbage, sabal palm
Taxodium distichum, baldcypress
Taxodium ascendens, pondcypress
Vaccinium arboreum, sparkleberry
Medium to high wind tolerance
Acer saccharum, Florida sugar maple
Acer palmatum, Japanese maple
Betula nigra, river birch
Carpinus caroliniana, ironwood
Carya glabra, pignut hickory
Carya tomentosa, mockemut hickory
Celtis occidentalis, Common hackberry
Cercis canadensis, red bud
Chionanthus virginicus, fringe tree
Diospyros virginiana, common persimmon
Fraxinus americana, white ash
Liquidambar styraciflua, sweetgum
Magnolia virginiana, sweetbay magnolia
Magnolia x soulangiana, saucer magnolia
Nyssa aquatica, water tupelo
Nyssa sylvatica, black tupelo
Ostrya virginiana, American hophornbeam
Prunus angustifolia, chickasaw plum
Quercus michauxii, swamp chestnut
Quercus shumardii, Shumard oak
Quercus stellata, post oak
Ulmus alata, winged elm
Tropical and Subtropical Region
Highest wind tolerance
Bursera simaruba, gumbo limbo
Butia capitata, pindo or jelly palm
Carya floridana, Florida scrub hickory
Conocarpus erectus, buttonwood
Chrysobalanus icaco, cocoplum
Coccothrinax argentata, Florida silver palm
Cordia sebestena, geiger tree
Dypsis lutescens, areca palm
Eugenia axillaris, white stopper
Eugenia confusa, redberry
Eugenia foetida, boxleaf stopper
Guaiacum sanctum, lignum vitae
Hyophorbe lagenicaulis, bottle palm
Hyophorbe verschaffeltii, spindle palm
Ilex cassine, dahoon holly
Krugiodendrum ferreum, ironwood
Lagerstroemia indica, crape myrtle
Latania loddigesii, blue latan palm
Livistona chinensis, Chinese fan palm
Magnolia grandiflora, southern magnolia
Phoenix canariensis, Canary Island date palm
Phoenix dactylifera, date palm
Phoenix reclinata, Senegal date palm
Phoenix roebelenii, pygmy date palm
Podocarpus spp, podocarpus
Ptychoesperma elegans, Alexander Sabal palmetto, cabbage, sabal palm
Quercus virginiana, live oak
Quercus geminata, sand live oak
Taxodium ascendens, pondcypress
Taxodium distichum, baldcypress
Thrinax morrisii, key thatch palm
Thrinax radiata, Florida thatch palm
Veitchia merrillii, Manila palm
Medium to High wind tolerance
Annona glabra, pond apple
Calophyllum calaba, Brazilian beautyleaf
Caryota mitis, fishtail palm
Chrysophyllum oliviforme, satinleaf
Coccoloba uvifera, sea grape
Coccoloba diversifolia, pigeon plum
Cocos nucifera, coconut palm
Dypsis decaryi, triangle palm
Liquidambar styraciflua, sweetgum
Litchi chinensis, lychee
Lysiloma latsiliqua, wild tamarind
Magnolia virginiana, sweetbay magnolia
Nyssa sylvatica, black tupelo
Roystonea elata, royal palm
Sideroxylon foetidissimum, mastic
Simarouba glauca, paradise tree
Swietenia mahagoni, mahogany
Note: Other trees are considered to have low to medium wind resistance.
Tree Selection
Other factors the arborist and landscape architect should consider includes removing over-mature and tree species at risk that have demonstrated poor survival in hurricanes. Then, during the reinstalling process, replace these tree species at risk with high-quality trees from the lists above.
- Choose wind-resistant species.
- Select the right tree for the right location. Look at the soils as well as the underground and overhead utilities.
- Select trees that have good central leaders and good structure.
- Begin a structural pruning program for young trees as described in Topic #17. Within two years after installation, co-dominant stems may develop bark inclusions, which are weak unions between branches and are very susceptible to breakage during hurricanes. To develop strong structure, both young and mature trees need to be managed with structural pruning as well as removing all or part of one co-dominant leader.
- Install a variety of species and ages.
- Install in layers of trees and shrubs to maintain diversity in the urban forest as well as buffering the wind.
- Install trees in groups or groves. Trees in groves survive winds better than trees growing individually. A grove is defined as a small wooded or forested area of at least three trees greater than 6 in (15 cm) dbh, usually with no undergrowth.
- Native species and their cultivars should receive strong consideration when selecting trees for the urban forest. Additional benefits of using native trees and their cultivars include their values for wildlife and native ecosystem conservation.
- Another important factor in designing a healthy urban landscape, is providing enough soil space for tree roots to grow. Tree roots need to extend out from a tree in all directions in order to stabilize it against wind throw. Never cut roots closer than the distance of 5 times the trunk diameter. To provide anchorage for the tree, give trees enough rooting space based on their mature size:
- Small trees need at least 10 feet by 10 feet (3x3x1m) of good soil area.
- Medium trees need 20 feet by 20 feet (6x6x1m) of area.
- Large trees need at least 30 feet by 30 feet (9x9x1m) of area.
- Make sure that planting sites have 3 feet (1m) of soil depth with a deep water table to allow a healthy root system development. The soil should not be compacted in any way, except with water at planting time.
Other Considerations
- When compared to broad-leaved trees and conifers, palms are not trees but are classified as large woody herbs, and have often been observed to be more resistant to hurricane force winds. Palms grow differently from other trees because they have one terminal bud. If that bud is not damaged, palms may lose all their fronds and still survive.
- Pines have been observed to be very sensitive to wind effects. They may show no immediate visible damage after high winds but may die sometime later. They can die slowly over a period of 6 months to 2 years after the high wind storms.
- The greater the wind speed, the more leaves trees lose. However, leaf loss does not mean the tree is dead. Instead, it means the tree is temporarily unable to photosynthesize and store energy. With time, the tree will produce new leaves which bring the tree back to good health.
- As trees grow and age, they become more susceptible to insects and diseases. Aging also causes branches and parts of the tree to begin to die. As they become less flexible, they may be more vulnerable to winds. Over-mature trees that present a risk to people and property should be removed prior to the hurricane and replaced with better trees. Old trees with decayed root systems, stem decay, or large dead branches are also vulnerable to breakage in hurricanes and should be replaced.
Trees that Survive Floods
Flooding may cause direct damage to trees by changing soil conditions, interrupting normal gas exchange, sedimentation, and physical damage. Flooding may also weaken trees and make them more susceptible to indirect damage from insects and diseases. Trees may need special care following a flood to minimize long-term decline. Flood damage may affect tree height, diameter growth, and tree survival because of soil changes, physical damage, insect invasions, and disease attacks. The potential for damage to trees from flooding depends on both the flood and the tree's characteristics.
Flood stressed trees exhibit a range of symptoms that include: leaf chlorosis and defoliation, reduced leaf size, early autumn coloration and leaf drop, development of epicormic shoots, crown dieback, and production of either large seed crops or no seed crops in years following a flood. Symptoms may progress and ultimately result in tree death over a period of several years or the symptoms may abate as the tree recovers.
Water covering the soil reduces the supply of oxygen to tree roots. Sediments carried by the water and deposited over the roots also reduce the supply of oxygen to tree roots. As little as three inches of sediment can be harmful.
Changes in Tree Growth Rate
A long-duration flood, especially during the growing season, may decrease height and diameter growth of tree species that are intolerant of flooding, but height and diameter growth may increase for flood tolerant species.
Decomposition of Organic Matter
The rate of decomposition of organic matter on flooded soil tends to be only one half of what it is in areas where soil is not flooded. The major end products of decomposition of organic matter in flooded soil are carbon dioxide, methane, and humic materials. In addition, the high concentrations of ethanol and hydrogen sulfide that are produced in waterlogged soil can damage tree roots. Flood waters may contain upstream chemicals from urban areas or agricultural fields that may be harmful to trees when absorbed by their roots.
Physical Damage
In contrast to sediment deposits over tree roots, strong currents, waves, or suspended particles may cause the soil around the base of trees to be washed away, exposing their roots. Exposed roots can stress trees and make them more vulnerable to wind-throw. Ice floes (floating ice) and debris carried by rushing waters can remove bark and damage tissues. Such wounds may then be subject to wood stain and decay organisms. Flood waters that cover foliage on lower branches will interfere with photosynthesis and gas exchange, leading to death of those branches.
Insect Damage
Stem boring insects are the major insect of concern following a flood. The most common stem borers are beetles, either adults or immature larvae depending on the species. They are serious pests because the damage they cause occurs in the tree’s phloem and outer sapwood layers. Wood borers weaken stems, which may lead to breakage during ice, wind or snowstorms.
It is unknown if leaf-feeding caterpillars or sucking insects (scales and aphids) become more of a problem following flooding. Plant stress can alter the biochemistry of trees making nutrients and sugars more available to insects feeding on leaves or sap. This could increase survival of these insects and increase their population size. Outbreaks of insects could further increase stress levels on trees severely weakened by a flood. Control of these insects should be considered a priority on high value trees for one to three years after a flood.
Disease Damage
Several diseases may weaken or kill trees following flooding. They mainly affect a tree’s roots, flare, and lower stem. The most likely is Armillaria root disease. Flood stressed trees are especially susceptible to flare and root rot diseases caused by species of Phytophthora and Pythium.
Flood Characteristics
Trees are more likely to be damaged by flooding during the growing season than by flooding during the dormant season. Trees are most susceptible to flood damage in late spring just after the first flush of growth. Tree species begin their spring flush at different times so the timing of a flood influences the species that are likely to be damaged.
Duration of a Flood
The duration of a flood also affects tree health and survival. Flooding displaces air in the soil leading to root decline or death. A well-drained soil for trees and shrubs allows water to drain at a rate of one inch (2.5 cm) per hour. A soil that is bad for trees percolates at a rate of 24 inches (60 cm) in seven to ten days. Fortunately, the soils in most flood zones contains high levels of sand and gravel particles because the smaller soil particles have washed away in previous floods.
If the water recedes before growth begins, flooding usually is not a problem. Most tree species can withstand one to four months of flooding during the dormant season. However, when flooding occurs during the growing season, one to two weeks of flooding can cause major, long-term damage to sensitive trees and shrubs, even death of some species. Other species can survive as long as three to five months in flooded situations.
Effects of Tree Characteristics
Tree tolerance to flooding depends on many characteristics including tree height, crown class, age, vigor, and species. Tree injury increases in proportion to the percent of crown covered by water. Some trees can survive with their main stems standing in several feet of water for months, but may die in less than one month if their foliage is completely covered. Few species can tolerate more than one month of complete submersion during the growing season. Mature trees survive flooding better than over-mature trees or seedlings of the same species.
Tree Tolerance to Flooding
There are differences in flood tolerance between trees of the same species. Flood tolerance may be an inherited trait. The recommendations listed below were reported by researchers in different geographic areas where the tree species mix varied, the flood events were different, and definitions of flooding tolerance varied.
Tree Lists
The following tree and shrubs species grow reliably in USDA Hardiness Zone 3 but may not be as tolerant in other regions.
Deciduous Trees Tolerant of Poorly Drained and Flooded Sites
Boxelder (Acer negundo)
Red maple (Acer rubrum)
Red Sunset maple (Acer r. saccharinum)
Silver maple (Acer saccharinum)
Ohio buckeye (Aesculus glabra)
Black alder (Alnus glutinosa)
White alder (Alnus incana)
Speckled alder (Alnus rugosa)
River birch (Betula nigra)
Paper birch (Betula papyrifera)
Northern catalpa (Catalpa speciosa)
Common hackberry (Celtis occidentalis)
Pagoda dogwood (Cornus alternifolia)
White ash (Fraxinus americana)
Black ash (Fraxinus nigra)
Green ash (Fraxinus pennsylvanica)
Tamarack (Larix laricina)
European larch (Larix decidua)
Sycamore (Platanus occidentalis)
Eastern cottonwood (Populus deltoides)
Bigtooth aspen (Populus grandidentata)
Waferash (Ptelea trifoliata)
Bicolor oak (Quercus bicolor)
Bur oak (Quercus macrocarpa)
Eastern pin oak (Quercus palustris)
Peachleaf willow (Salix amygdaloides)
White willow (Salix alba)
Black willow (Salix nigra)
Showy Mountain-ash (Sorbus decora)
Baldcypress (Taxodium distichum)
American elm (Ulmus americana)
Evergreen Trees Tolerant of Poorly Drained and Flooded Sites
White spruce (Picea glauca)
Black spruce (Picea mariana)
Northern white-cedar (Thuja occidentalis)
Canadian hemlock (Tsuga canadensis)
Able to Survive Prolonged Flooding for More than 1 year
Buttonbush (Cephalanthus occidentalis)
Green ash (Fraxinus pennsylvanica)
Black willow (Salix nigra)
Able to Survive Prolonged Flooding for More than 1 year but Significant Mortality if Repeated
Boxelder (Acer negundo)
Red maple (Acer rubrum)
Silver maple (Acer saccharinum)
Hackberry (Celtis occidentalis)
White ash (Fraxinus americana)
Sweetgum (Liquidambar styraciflua)
Sycamore (Platanus occidentalis)
Eastern cottonwood (Populus deltoides)
Pin oak (Quercus palustris)
Tolerant of More than 150 Days of Flooding during the Growing Season
Downy hawthorn (Crataegus mollis)
Honeylocust (Gleditsia triacanthos)
Swamp white oak (Quercus bicolor)
Pin oak (Quercus palustris)
Somewhat Tolerant of 90 – 150 Days of Flooding
Shagbark hickory (Carya ovata)
Hackberry (Celtis occidentalis)
Redbud (Cercis canadensis)
Black walnut (Juglans nigra)
Green ash (Fraxinus pennsylvanica)
American elm (Ulmus americana)
Tree Care After a Flood
Flooding may cause direct damage to trees by changing soil conditions, interrupting normal gas exchange, sedimentation, and physical damage. Flooding may also weaken trees and make them more susceptible to indirect damage from insects and diseases. Trees may need special care following a flood to minimize long-term decline. Flood damage may affect tree height, diameter growth, and tree survival because of soil changes, physical damage, insect invasions, and disease attacks. The potential for damage to trees from flooding depends on both the flood and the tree's characteristics.
Flood stressed trees exhibit a range of symptoms that include: leaf chlorosis and defoliation, reduced leaf size, early autumn coloration and leaf drop, development of epicormic shoots, crown dieback, and production of either large seed crops or no seed crops in years following a flood. Symptoms may progress and ultimately result in tree death over a period of several years or the symptoms may abate as the tree recovers.
Water covering the soil reduces the supply of oxygen to tree roots. Sediments carried by the water and deposited over the roots also reduce the supply of oxygen to tree roots. As little as three inches of sediment can be harmful.
Changes in Tree Growth Rate
A long-duration flood, especially during the growing season, may decrease height and diameter growth of tree species that are intolerant of flooding, but height and diameter growth may increase for flood tolerant species.
Decomposition of Organic Matter
The rate of decomposition of organic matter on flooded soil tends to be only one half of what it is in areas where soil is not flooded. The major end products of decomposition of organic matter in flooded soil are carbon dioxide, methane, and humic materials. In addition, the high concentrations of ethanol and hydrogen sulfide that are produced in waterlogged soil can damage tree roots. Flood waters may contain upstream chemicals from urban areas or agricultural fields that may be harmful to trees when absorbed by their roots.
Physical Damage
In contrast to sediment deposits over tree roots, strong currents, waves, or suspended particles may cause the soil around the base of trees to be washed away, exposing their roots. Exposed roots can stress trees and make them more vulnerable to wind-throw. Ice floes (floating ice) and debris carried by rushing waters can remove bark and damage tissues. Such wounds may then be subject to wood stain and decay organisms. Flood waters that cover foliage on lower branches will interfere with photosynthesis and gas exchange, leading to death of those branches.
Insect Damage
Stem boring insects are the major insect of concern following a flood. The most common stem borers are beetles, either adults or immature larvae depending on the species. They are serious pests because the damage they cause occurs in the tree’s phloem and outer sapwood layers. Wood borers weaken stems, which may lead to breakage during ice, wind or snowstorms.
It is unknown if leaf-feeding caterpillars or sucking insects (scales and aphids) become more of a problem following flooding. Plant stress can alter the biochemistry of trees making nutrients and sugars more available to insects feeding on leaves or sap. This could increase survival of these insects and increase their population size. Outbreaks of insects could further increase stress levels on trees severely weakened by a flood. Control of these insects should be considered a priority on high value trees for one to three years after a flood.
Disease Damage
Several diseases may weaken or kill trees following flooding. They mainly affect a tree’s roots, flare, and lower stem. The most likely is Armillaria root disease. Flood stressed trees are especially susceptible to flare and root rot diseases caused by species of Phytophthora and Pythium.
Flood Characteristics
Trees are more likely to be damaged by flooding during the growing season than by flooding during the dormant season. Trees are most susceptible to flood damage in late spring just after the first flush of growth. Tree species begin their spring flush at different times so the timing of a flood influences the species that are likely to be damaged.
Duration of a Flood
The duration of a flood also affects tree health and survival. Flooding displaces air in the soil leading to root decline or death. A well-drained soil for trees and shrubs allows water to drain at a rate of one inch (2.5 cm) per hour. A soil that is bad for trees percolates at a rate of 24 inches (60 cm) in seven to ten days. Fortunately, the soils in most flood zones contains high levels of sand and gravel particles because the smaller soil particles have washed away in previous floods.
If the water recedes before growth begins, flooding usually is not a problem. Most tree species can withstand one to four months of flooding during the dormant season. However, when flooding occurs during the growing season, one to two weeks of flooding can cause major, long-term damage to sensitive trees and shrubs, even death of some species. Other species can survive as long as three to five months in flooded situations.
Effects of Tree Characteristics
Tree tolerance to flooding depends on many characteristics including tree height, crown class, age, vigor, and species. Tree injury increases in proportion to the percent of crown covered by water. Some trees can survive with their main stems standing in several feet of water for months, but may die in less than one month if their foliage is completely covered. Few species can tolerate more than one month of complete submersion during the growing season. Mature trees survive flooding better than over-mature trees or seedlings of the same species.
Tree Tolerance to Flooding
There are differences in flood tolerance between trees of the same species. Flood tolerance may be an inherited trait. The recommendations listed below were reported by researchers in different geographic areas where the tree species mix varied, the flood events were different, and definitions of flooding tolerance varied.
Tree Lists
The following tree and shrubs species grow reliably in USDA Hardiness Zone 3 but may not be as tolerant in other regions.
Deciduous Trees Tolerant of Poorly Drained and Flooded Sites
Boxelder (Acer negundo)
Red maple (Acer rubrum)
Red Sunset maple (Acer r. saccharinum)
Silver maple (Acer saccharinum)
Ohio buckeye (Aesculus glabra)
Black alder (Alnus glutinosa)
White alder (Alnus incana)
Speckled alder (Alnus rugosa)
River birch (Betula nigra)
Paper birch (Betula papyrifera)
Northern catalpa (Catalpa speciosa)
Common hackberry (Celtis occidentalis)
Pagoda dogwood (Cornus alternifolia)
White ash (Fraxinus americana)
Black ash (Fraxinus nigra)
Green ash (Fraxinus pennsylvanica)
Tamarack (Larix laricina)
European larch (Larix decidua)
Sycamore (Platanus occidentalis)
Eastern cottonwood (Populus deltoides)
Bigtooth aspen (Populus grandidentata)
Waferash (Ptelea trifoliata)
Bicolor oak (Quercus bicolor)
Bur oak (Quercus macrocarpa)
Eastern pin oak (Quercus palustris)
Peachleaf willow (Salix amygdaloides)
White willow (Salix alba)
Black willow (Salix nigra)
Showy Mountain-ash (Sorbus decora)
Baldcypress (Taxodium distichum)
American elm (Ulmus americana)
Evergreen Trees Tolerant of Poorly Drained and Flooded Sites
White spruce (Picea glauca)
Black spruce (Picea mariana)
Northern white-cedar (Thuja occidentalis)
Canadian hemlock (Tsuga canadensis)
Able to Survive Prolonged Flooding for More than 1 year
Buttonbush (Cephalanthus occidentalis)
Green ash (Fraxinus pennsylvanica)
Black willow (Salix nigra)
Able to Survive Prolonged Flooding for More than 1 year but Significant Mortality if Repeated
Boxelder (Acer negundo)
Red maple (Acer rubrum)
Silver maple (Acer saccharinum)
Hackberry (Celtis occidentalis)
White ash (Fraxinus americana)
Sweetgum (Liquidambar styraciflua)
Sycamore (Platanus occidentalis)
Eastern cottonwood (Populus deltoides)
Pin oak (Quercus palustris)
Tolerant of More than 150 Days of Flooding during the Growing Season
Downy hawthorn (Crataegus mollis)
Honeylocust (Gleditsia triacanthos)
Swamp white oak (Quercus bicolor)
Pin oak (Quercus palustris)
Somewhat Tolerant of 90 – 150 Days of Flooding
Shagbark hickory (Carya ovata)
Hackberry (Celtis occidentalis)
Redbud (Cercis canadensis)
Black walnut (Juglans nigra)
Green ash (Fraxinus pennsylvanica)
American elm (Ulmus americana)
Tree Care After a Flood
- Trees that are healthy before a flood are more likely to survive flooding in good condition.
- To increase tree vigor, apply a low nitrogen fertilizer, aerate the soil, mulch around the base of small trees to eliminate weeds, and conserve moisture; then irrigate if soil conditions become excessively dry too fast after the flood.
- Remove branches that are broken, cankered or dead, but prune trees only when bark surfaces are dry or during the dormant season to minimize infection.
- Remove sediment deposited over the roots by the flood.
- Large trees that have been partially uprooted may need to be removed. Reset small, easy-to-manage
trees. Stabilize the tree's roots until the tree becomes reestablished.
Trees that Survive Storm Surges
If you live near the ocean, the storm surge is the most dangerous part of a storm. The storm surge is water that is pushed onto the shore by an ocean storm. It is rarely a "wall of water" as often assumed, but rather a rise of water in waves that can be as rapid as several feet in just a few minutes. A storm surge moves with the forward speed of 10 – 15 mph (16-24 kph). This wind-driven water has tremendous power. A cubic yard (0.8 cubic meter) of sea water weighs 1,728 pounds (800 kilograms). It is difficult to stand in a six-inch (15 cm) surge and a one-foot (30 cm) deep storm surge can sweep your car off the road. Compounding the destructive power of the rushing water is the large amount of debris that typically accompanies the surge. Trees, pieces of buildings, and other debris floating on top of the waves along with stones from the ocean floor, act as battering rams that can cave in any building or sea wall unfortunate enough to be in the way.
Maritime Forests
An answer for a buffer against the storm surge as well as what will grow along the ocean front requires looking at maritime forests. A maritime forest is a coastal wooded habitat found on higher ground than dune areas and is within range of salt spray. Maritime forests are comprised of deciduous, coniferous, and broadleaf evergreens. The trees have large roots that anchor the sand and this helps to keep the sand in place instead of blowing or washing away.
Trees in maritime forests survive the strong winds by growing close together. They form a tight, smooth canopy with their branches. This lets the wind blow over and around the trees without blowing them down. It also protects the trees from concentrated salt spray. The tight canopy provides shade that helps conserve water by reducing evaporation and transpiration from the leaves. The trees in the maritime forest need one another. If the maritime forest was cut down and a lone tree was left behind, it would die. There would be nothing to protect it from the wind, the sun, and the salt spray.
There are many good things that trees get in return for living on the ocean front. They get a constant supply of nutrients from light doses of the salt spray. The warm winters and long growing season make it easier for the trees to grow.
Between the maritime forests and the ocean are sand dunes. More than just sand, these dune are covered with dune grass and small, salt tolerant shrubs. The grass and shrubs form thick mats of roots just below the surface and they provide the first line of defense against normal wave action. They do not provide much protection from a storm surge. This is when the maritime forests provide protection.
Mangrove Forests
Because the soil in shallow areas of warm climate maritime forests are typically flooded during high tides, salt marsh grasses, mangrove trees, and other estuarine plants all work together to prevent erosion and stabilize the shoreline. Many species of mangrove trees have developed aerial roots that take in oxygen from the air for use by the tree. Some species also have prop roots extending from the trunk that helps them withstand the destructive action of tides, waves, and storm surges. All mangrove species have laterally spreading roots that are very shallow.
Mangrove trees have become specialized to survive in this habitat. Two key adaptations they have are:
1) the ability to survive in waterlogged soil and soil with no oxygen,
2) the ability to tolerate brackish waters.
Live Oak Forests
The live oak forest is the predominant climax community of southern barrier islands. This means that, under prevailing physical circumstances, this climax community continues to propagate itself and tends to remain relatively unchanged over time. Disruptive events like fires, hurricanes, blights, or human influence may temporarily cause new and different communities to form (i.e. fields, pine forests, swamps), but over time these eventually succeed back to the live oak climax community.
The clearing of land to obtain timber, the construction of homes and roads, and other development projects completed without properly replanting the area can lead to excessive sediments being washed into the ocean. Without the forest protection, the homes and roads will be lost during the next major storm surge.
Tree List
The trees that are listed below have been selected by researchers who listed trees as those that have survived storm surges and have prevented potential storm surge damage to properties and the forest.
Acer barbatum, Southern sugar maple
Acer rubrum, Red maple
Aesculus pavia, Red buckeye
Albizia julibrissin, Mimosa
Amelanchier canadensis, Serviceberry
Betula nigra, River birch
Carpinus caroliniana, Ironwood
Carya cordiformis, Bitternut hickory
Carya glabra, Pignut hickory
Carya illinoinensis, Pecan
Carya myristiciformis, Nutmeg hickory
Carya ovalis, Red hickory
Carya pallida, Sand hickory
Carya tomentosa, Mockernut hickory
Castanea pumila, Chinquapin
Catalpa spp. Catalpa
Celtis laevigata, Sugarberry
Cercis canadensis, Eastern redbud
Chamaecyparis thyoides, Atlantic white-cedar
Chionanthus virginicus, Fringetree
Cornus asperifolia, Roughleaf dogwood
Cornus florida, Flowering dogwood
Cornus stricta, Swamp dogwood
Crataegus spp. Hawthorn
Cyrilla racemiflora, Titi
Diospyros virginiana, Persimmon
Fagus grandifolia, American beech
Fraxinus americana, White ash
Fraxinus caroliniana, Carolina ash
Fraxinus pennsylvanica, Green ash
Fraxinus profunda, Pumpkin ash
Gordonia lasianthus, Loblolly bay
Hamamelis virginiana, Witchhazel
Ilex opaca, American holly
Ilex vomitoria, Yaupon holly
Juniperus virginiana var. silicicola, Southern redcedar
Lagerstroemia indica, Crapemyrtle
Liquidambar styraciflua, Sweetgum
Liriodendron tulipifera, Tulip-poplar
Magnolia grandiflora, Southern magnolia
Magnolia virginiana, Sweetbay magnolia
Melia azedarach, Chinaberry
Morus rubra, Red mulberry
Myrica cerifera, Southern waxmyrtle
Myrica pensylvanica, Northern bayberry
Nyssa aquatica, Water tupelo
Nyssa biflora, Swamp tupelo
Nyssa sylvatica, Black tupelo
Ostrya virginiana, Hop hornbeam
Oxydendrum arboreum, Sourwood
Persea borbonia, Redbay
Persea palustris, Swamp redbay
Pinus elliottii, Slash pine
Pinus palustris, Longleaf pine
Pinus serotina, Pond pine
Pinus taeda, Loblolly pine
Pinus thunbergiana
Platanus occidentalis, American sycamore
Populus alba, White poplar
Prunus angustifolia, Chickasaw plum
Prunus caroliniana, Carolina cherry-laurel
Prunus serotina, Black cherry
Quercus alba, White oak
Quercus coccinea, Scarlet oak
Quercus falcata, Southern red oak
Quercus geminata, Sand live oak
Quercus hemisphaerica, Laurel oak
Quercus incana, Bluejack oak
Quercus laevis, Turkey oak
Quercus lurifolia, Swamp laurel oak
Quercus margarettiae, Sand post oak
Quercus merilandica, Blackjack oak
Quercus michauxii, Swamp chestnut oak
Quercus mniima
Quercus nigra, Water oak
Quercus pagoda
Quercus phellos, Willow oak
Quercus shumardii, Shumard oak
Quercus stellata, Post oak
Quercus virginiana, Live oak
Rhus copallina, Shining sumac
Sabal palmetto, Cabbage palm
Salix caroliniana, Swamp willow
Salix nigra, Black willow
Sassafras albidum, Sassafras
Symplocos tinctoria
Taxodium distichum, Bald cypress
Taxodium ascendens, Pond cypress
Toxicodendron vernix, Poison sumac
Ulmus americana, American elm
Ulmus rubra, Slippery elm
If you live near the ocean, the storm surge is the most dangerous part of a storm. The storm surge is water that is pushed onto the shore by an ocean storm. It is rarely a "wall of water" as often assumed, but rather a rise of water in waves that can be as rapid as several feet in just a few minutes. A storm surge moves with the forward speed of 10 – 15 mph (16-24 kph). This wind-driven water has tremendous power. A cubic yard (0.8 cubic meter) of sea water weighs 1,728 pounds (800 kilograms). It is difficult to stand in a six-inch (15 cm) surge and a one-foot (30 cm) deep storm surge can sweep your car off the road. Compounding the destructive power of the rushing water is the large amount of debris that typically accompanies the surge. Trees, pieces of buildings, and other debris floating on top of the waves along with stones from the ocean floor, act as battering rams that can cave in any building or sea wall unfortunate enough to be in the way.
Maritime Forests
An answer for a buffer against the storm surge as well as what will grow along the ocean front requires looking at maritime forests. A maritime forest is a coastal wooded habitat found on higher ground than dune areas and is within range of salt spray. Maritime forests are comprised of deciduous, coniferous, and broadleaf evergreens. The trees have large roots that anchor the sand and this helps to keep the sand in place instead of blowing or washing away.
Trees in maritime forests survive the strong winds by growing close together. They form a tight, smooth canopy with their branches. This lets the wind blow over and around the trees without blowing them down. It also protects the trees from concentrated salt spray. The tight canopy provides shade that helps conserve water by reducing evaporation and transpiration from the leaves. The trees in the maritime forest need one another. If the maritime forest was cut down and a lone tree was left behind, it would die. There would be nothing to protect it from the wind, the sun, and the salt spray.
There are many good things that trees get in return for living on the ocean front. They get a constant supply of nutrients from light doses of the salt spray. The warm winters and long growing season make it easier for the trees to grow.
Between the maritime forests and the ocean are sand dunes. More than just sand, these dune are covered with dune grass and small, salt tolerant shrubs. The grass and shrubs form thick mats of roots just below the surface and they provide the first line of defense against normal wave action. They do not provide much protection from a storm surge. This is when the maritime forests provide protection.
Mangrove Forests
Because the soil in shallow areas of warm climate maritime forests are typically flooded during high tides, salt marsh grasses, mangrove trees, and other estuarine plants all work together to prevent erosion and stabilize the shoreline. Many species of mangrove trees have developed aerial roots that take in oxygen from the air for use by the tree. Some species also have prop roots extending from the trunk that helps them withstand the destructive action of tides, waves, and storm surges. All mangrove species have laterally spreading roots that are very shallow.
Mangrove trees have become specialized to survive in this habitat. Two key adaptations they have are:
1) the ability to survive in waterlogged soil and soil with no oxygen,
2) the ability to tolerate brackish waters.
Live Oak Forests
The live oak forest is the predominant climax community of southern barrier islands. This means that, under prevailing physical circumstances, this climax community continues to propagate itself and tends to remain relatively unchanged over time. Disruptive events like fires, hurricanes, blights, or human influence may temporarily cause new and different communities to form (i.e. fields, pine forests, swamps), but over time these eventually succeed back to the live oak climax community.
The clearing of land to obtain timber, the construction of homes and roads, and other development projects completed without properly replanting the area can lead to excessive sediments being washed into the ocean. Without the forest protection, the homes and roads will be lost during the next major storm surge.
Tree List
The trees that are listed below have been selected by researchers who listed trees as those that have survived storm surges and have prevented potential storm surge damage to properties and the forest.
Acer barbatum, Southern sugar maple
Acer rubrum, Red maple
Aesculus pavia, Red buckeye
Albizia julibrissin, Mimosa
Amelanchier canadensis, Serviceberry
Betula nigra, River birch
Carpinus caroliniana, Ironwood
Carya cordiformis, Bitternut hickory
Carya glabra, Pignut hickory
Carya illinoinensis, Pecan
Carya myristiciformis, Nutmeg hickory
Carya ovalis, Red hickory
Carya pallida, Sand hickory
Carya tomentosa, Mockernut hickory
Castanea pumila, Chinquapin
Catalpa spp. Catalpa
Celtis laevigata, Sugarberry
Cercis canadensis, Eastern redbud
Chamaecyparis thyoides, Atlantic white-cedar
Chionanthus virginicus, Fringetree
Cornus asperifolia, Roughleaf dogwood
Cornus florida, Flowering dogwood
Cornus stricta, Swamp dogwood
Crataegus spp. Hawthorn
Cyrilla racemiflora, Titi
Diospyros virginiana, Persimmon
Fagus grandifolia, American beech
Fraxinus americana, White ash
Fraxinus caroliniana, Carolina ash
Fraxinus pennsylvanica, Green ash
Fraxinus profunda, Pumpkin ash
Gordonia lasianthus, Loblolly bay
Hamamelis virginiana, Witchhazel
Ilex opaca, American holly
Ilex vomitoria, Yaupon holly
Juniperus virginiana var. silicicola, Southern redcedar
Lagerstroemia indica, Crapemyrtle
Liquidambar styraciflua, Sweetgum
Liriodendron tulipifera, Tulip-poplar
Magnolia grandiflora, Southern magnolia
Magnolia virginiana, Sweetbay magnolia
Melia azedarach, Chinaberry
Morus rubra, Red mulberry
Myrica cerifera, Southern waxmyrtle
Myrica pensylvanica, Northern bayberry
Nyssa aquatica, Water tupelo
Nyssa biflora, Swamp tupelo
Nyssa sylvatica, Black tupelo
Ostrya virginiana, Hop hornbeam
Oxydendrum arboreum, Sourwood
Persea borbonia, Redbay
Persea palustris, Swamp redbay
Pinus elliottii, Slash pine
Pinus palustris, Longleaf pine
Pinus serotina, Pond pine
Pinus taeda, Loblolly pine
Pinus thunbergiana
Platanus occidentalis, American sycamore
Populus alba, White poplar
Prunus angustifolia, Chickasaw plum
Prunus caroliniana, Carolina cherry-laurel
Prunus serotina, Black cherry
Quercus alba, White oak
Quercus coccinea, Scarlet oak
Quercus falcata, Southern red oak
Quercus geminata, Sand live oak
Quercus hemisphaerica, Laurel oak
Quercus incana, Bluejack oak
Quercus laevis, Turkey oak
Quercus lurifolia, Swamp laurel oak
Quercus margarettiae, Sand post oak
Quercus merilandica, Blackjack oak
Quercus michauxii, Swamp chestnut oak
Quercus mniima
Quercus nigra, Water oak
Quercus pagoda
Quercus phellos, Willow oak
Quercus shumardii, Shumard oak
Quercus stellata, Post oak
Quercus virginiana, Live oak
Rhus copallina, Shining sumac
Sabal palmetto, Cabbage palm
Salix caroliniana, Swamp willow
Salix nigra, Black willow
Sassafras albidum, Sassafras
Symplocos tinctoria
Taxodium distichum, Bald cypress
Taxodium ascendens, Pond cypress
Toxicodendron vernix, Poison sumac
Ulmus americana, American elm
Ulmus rubra, Slippery elm
Trees that Survive Drought
Some decrease in tree growth or flowering can be expected during a long period of limited moisture. Severe drought can result in trees having a decreased resistance to insect and disease invasions, a decrease in leaf size and number, and an overall decline in growth rate and vigor. High temperatures and wind, heat and light reflection from nearby hard surfaces, and high fertilization rates can increase the potentially damaging effects of low moisture on tree growth and survival.
Tree Care
Trees are one of the best investments in areas which experience low water availability. While they need to be regularly watered in a limited area for the first three years of growth, once they become established, the root system has developed to where it can obtain water from the environment. Most trees require very little irrigation water after establishment. Dead plant tissues and mulch decomposition provide organic matter to the soil, which will increase soil infiltration and capacity rates of water, and reduce water run-off. Trees shade the ground and reduce the heat and evaporation caused by direct sunlight, which in turn, allows better water infiltration into the soil. Trees (after establishment) do not require their entire root system to receive water in order to survive. By comparison, trees require less water per canopy area than landscape shrubs, flowers, and turf.
Best Management Practices
The following are some best management practices for responding to water resource challenges during reduced water availability such as droughts:
Water Tips for Home and Work
The following are some best management practices for responding to water resource challenges during reduced water availability:
Reduce Water Use
Along with water tips, there are many other ways to reduce water use that will provide water capacity for landscapes.
Some decrease in tree growth or flowering can be expected during a long period of limited moisture. Severe drought can result in trees having a decreased resistance to insect and disease invasions, a decrease in leaf size and number, and an overall decline in growth rate and vigor. High temperatures and wind, heat and light reflection from nearby hard surfaces, and high fertilization rates can increase the potentially damaging effects of low moisture on tree growth and survival.
Tree Care
Trees are one of the best investments in areas which experience low water availability. While they need to be regularly watered in a limited area for the first three years of growth, once they become established, the root system has developed to where it can obtain water from the environment. Most trees require very little irrigation water after establishment. Dead plant tissues and mulch decomposition provide organic matter to the soil, which will increase soil infiltration and capacity rates of water, and reduce water run-off. Trees shade the ground and reduce the heat and evaporation caused by direct sunlight, which in turn, allows better water infiltration into the soil. Trees (after establishment) do not require their entire root system to receive water in order to survive. By comparison, trees require less water per canopy area than landscape shrubs, flowers, and turf.
Best Management Practices
The following are some best management practices for responding to water resource challenges during reduced water availability such as droughts:
- Deeply soak trees and shrubs only after they show initial signs of water stress, and apply water in the morning or evening during periods of low sun and heat, (between 9 pm and 9 am) to prevent excessive evaporation.
- Use a drip emitter, soaker hose, targeted bubbler, watering bags or low-flow garden hose to direct water to the tree roots (not the trunk), and allow the water to slowly seep deep into the soil. A slow trickle is the most effective method for absorption. Watering bags are an excellent mechanism for providing a slow drip of water that trickles into the soil. Watering with a hose at high speed usually results in run-off and rapid evaporation, and encourages root growth near the surface, thereby increasing the tree’s susceptibility to
water stress.
- Cover bare soil with mulch to retain more soil moisture. Irrigation should be set so it wets the soil under the mulch, or irrigates long enough to thoroughly saturate the mulch area and the soil under it.
- Autumn installed trees and shrubs have demonstrated an increased ability to survive moderate moisture levels compared to those transplanted in the spring or summer.
- Adding mycorrhizal fungi inoculants when installing trees has mixed results. Mycorrhizae do attach to tree roots and transfer small amounts of moisture and minerals from the soil to the tree roots. Once the fungi are established, they will seek water from soil pores too small for tree roots to access. However, purchasing the mycorrhizae inoculants often have no viable spores in the package, so nothing happens to benefit the tree. Mycorrhizae often die in heat, drought or prolonged time in packaging. Mycorrhizae inoculants can be added to the roots of established trees by soil injection and many arborists and landscape architects prefer to take a shovel full of soil from around the roots of a nearby established tree, to provide the essential mycorrhizal fungi around the roots as part of the installation process.
Water Tips for Home and Work
The following are some best management practices for responding to water resource challenges during reduced water availability:
- Gray water is water that has been used in the home, except water from toilets. Dish, shower, sink, and laundry water comprise 50-80% of residential "waste" water. This water may be reused for other purposes, especially landscape irrigation after testing for phosphates and salts. This practice will require re-plumbing the home.
- Collecting stormwater that may otherwise leave one's property via the stormwater collection system is a simple way to retain irrigation water. Cisterns, rain barrels, and collection tanks intercepting roof runoff can provide non-potable water to irrigate landscapes and trees.
- Use cultural practices such as such as mowing lawns higher and controlling water runoff on slopes will lower water needs in the landscape.
- Lawns that are typically watered for short periods of time, several times a week in hot weather, should have one long watering overnight.
- Trees and shrubs require watering for longer periods but less frequently than grass and should be on separate zones or valves from turf to provide the correct amount of water.
- Is the lawn really necessary? Consider re-landscaping with low-water-using trees and shrubs where lawn is not needed. Monitor tree water use and irrigate only to meet the tree's needs.
- Add hydrogels to the soil around trees that dry out quickly. These water-absorbing polymer crystals swell to several times their original size and slowly release water into the surrounding soil.
- Perform regular maintenance on irrigation systems and regular adjustment to irrigation controllers as the weather changes.
- "Shower with a friend" take a bucket (or more) into the shower to collect water that would run down the drain. These buckets can be placed directly on a new tree's root ball to help establish a tree during a drought or water rationing restriction. This practice will also require re-plumbing the home.
- Install a separate landscape water meter for monitoring water use and leak detection. Cities that have sewerage systems will have lower rates for landscape water because it will not need treatment.
- A tree needs 5 gallons (19 liters) of water plus 5 gallons for each inch of dbh. For example: a tree with a dbh of 10" (25 cm) needs 55 gallons (200 liters) of water per week to roughly equal 1" (2.5 cm) of rainfall.
Reduce Water Use
Along with water tips, there are many other ways to reduce water use that will provide water capacity for landscapes.
- Sweep pavement and driveways instead of hosing them down.
- Use hoses with a shutoff valve to prevent water loss from leaks.
- Use a shutoff nozzle when washing cars or go to a water recycling car wash facility.
- Check the swimming pool and equipment for water leaks.
- Cover swimming pool during the day, when not in use, to reduce evaporation and warm the water.
Planting Trees During a Drought
Installing smaller trees 2 in. (5 cm) or less caliper for deciduous trees and 6 feet (1.8 m) or less height for evergreen trees, reduces the monetary investment and increases the survival rate of installation during drought periods. Installing smaller trees allows the tree to establish more quickly than installing a large tree and will require less maintenance over time.
Why Plant Trees During a Drought?
Installing trees and shrubs during drought can be risky. If watering restrictions are in place, establishing trees in a semi-arid region may be difficult enough without an extended drought to contend with. However, by eliminating all tree plantings, opportunities to sustain the urban forest may be missed. It is critical to not only have diversity of species in the landscape but also a diversity of age among those species in the landscape. This means installing new and replacement trees each year, even during times of drought, to replace trees that will be lost to age, injury, drought, and other causes.
Carefully installed trees continues to maintain soil stability, reduce soil erosion, control and utilize storm water runoff, shade moisture-starved lawns and reduce energy usage by shading homes in summer and blocking winds in winter. A well-stocked urban forest also acts as an air filter and purifier, absorbing carbon dioxide and emitting oxygen to help provide cleaner air.
Some plants are more tolerant of drought stress. This may be attributed to an aggressive, deep root system or thickened, waxy leaves. Drought tolerance may also be attributed to physiological responses within the plant.
Large Drought Tolerant Trees
Scientific Name Common Name
Acer leucoderme Chalkbark maple
Acer platanoides Norway maple
Acer pseudoplatanus Sycamore maple
Acer rubrum Red maple
Acer x freemanii Freeman maple
Alnus glutinosa Common alder
Betula lenta Sweet birch
Calocedrus decurrens Incense cedar
Carpinus betulus European hornbeam
Carya illinoensis Pecan
Castanea sativa Spanish chestnut
Catalpa speciosa Northern catalpa
Cedrus atlantica 'Glauca' Blue atlas cedar
Cedrus deodara Deodar cedar
Cedrus libani Cedar of Lebanon
Celtis laevigata Hackberry
Celtis occidentalis Hackberry
Cladrastis kentuckea Yellowwood
Cryptomeria japonica
Cryptomeria Cunninghamia lanceolata China fir
Cupressus arizonica Arizona cypress
Eucommia ulmoides Hardy rubber tree
Fraxinus americana White ash (in non-EAB infested areas)
Fraxinus pennsylvanica Green ash (in non-EAB infested areas)
Ginkgo biloba (male) Ginkgo
Gleditsia triacanthos Honeylocust
Gleditsia triacanthos inermis Thornless honeylocust
Gymnocladus dioicus Kentucky coffeetree
Ilex opaca American holly
Juniperus saliciola Southern red cedar
Juniperus virginiana Eastern red cedar
Kalopanax pictus Castor-aralia
Liquidambar styraciflua Sweetgum
Maclura pomifera Osage-orange
Magnolia grandiflora Southern magnolia
Metasequoia stroboscopes Dawn redwood
Nyssa ogeche Ogeche gum
Oxydendrum arboreum Sourwood
Phellodendron amurense Amur cork tree
Picea glauca Alberta spruce
Picea pungens Colorado blue spruce
Pinus bungeana Lacebark pine
Pinus cembra Swiss stone pine
Pinus echinata Shortleaf pine
Pinus elliottii Slash pine
Pinus flexilis Limber pine
Pinus heldreichii Bosnian pine
Pinus koraiensis Korean pine
Pinus mugo Mugo pine
Pinus nigra Austrian pine
Pinus rigida Pitch pine
Pinus sylvestris Scotch pine
Pinus taeda Loblolly pine
Pinus thunbergiana Japanese black pine
Pinus virginiana Virginia pine P
inus wallichiana Himalayan pine
Platanus acerifolia London plane tree
Pyrus calleryana cvs. Cleveland, Aristocrat, Capital, New Bradford, Redspire
Quercus acutissima Sawtooth oak
Quercus alba White oak
Quercus bicolor Swamp white oak
Quercus coccinea Scarlet oak
Quercus falcata Southern red oak
Quercus hemisphaerica Darlington oak
Quercus imbricaria Shingle oak
Quercus lyrata Overcup oak
Quercus macrocarpa Bur oak
Quercus nigra Water oak
Quercus nuttalii Nuttall oak
Quercus palustris Pin oak
Quercus phellos Willow oak
Quercus prinus Chestnut oak
Quercus rubra Red oak
Quercus shumardii Shumard oak
Quercus stellata Post oak
Quercus virginiana Live oak
Robinia pseudoacacia Black locust
Sassafras albidum Sassafras
Taxodium ascendens Pond cypress
Taxodium distichum Baldcypress
Tilia americana American linden
Tilia cordata Littleleaf linden
Tilia tomentosa Silver linden
Ulmus alata Winged elm
Ulmus americana cvs. Liberty, Valley Forge Ulmus parvifolia Lacebark elm
Zelkova serrata Zelkova
Small Drought Tolerant Trees
Scientific Name Common Name
Acer barbatum Southern sugar maple
A. saccharum ssp. floridanum
Acer buergeranum Trident maple
Acer campestre Hedge maple
Acer ginnala Amur maple
Acer leucoderme Whitebark maple, calk maple
Acer negundo Boxelder
Acer truncatum Purple blow maple
Aesculus californica California buckeye
Aesculus pavia Red buckeye
Albizia julibrissin Mimosa
Alnus japonica Japanese alder
Alnus serrulata Tag alder
Carpinus betulus European Hornbeam
Carpinus betulus fastigiata Upright European hornbeam
Carpinus caroliniana American hornbeam, Ironwood
Carpinus japonica Japanese hornbeam
Carpinus orientalis Oriental hornbeam
Cercis canadensis Eastern redbud
Cercis canadensis ssp retisus Oklahoma redbud
Cercis canadensis ssp. texensis Texas redbud
Cercis chinensis Chinese redbud
Chionanthus retusus Chinese fringe tree
Cornus mas Cornelian cherry dogwood
Cotinus coggygria Smoketree
Cotinus hybrids Grace
Cotinus obovatus American smoke tree
Crataegus crus-galli Cockspur hawthorn
Crataegus laevigata Scarlet hawthorn, English hawthorn
Crataegus phaenopyrum Washington hawthorn
Crataegus x lavallei Lavalle hawthorn
Crataegus viridis Green hawthorn
Cupressus sempervirens Italian cypress
Cydonia sinensis Chinese quince
Cupressus arizonica cvs. Arizona cypress
Elaeagnus angustifolia Russian olive
Euscaphis japonica Korean sweetheart tree
Heptacodium miconiodes Seven-son flower
Hovenia dulcis Japanese raisin tree
Ilex ‘China Boy’, ‘China Girl’ China holly
Ilex cassine Dahoon holly
Ilex cornuta cvs. Burfordii, D’Or, O’ Spring
Ilex decidua Possumhaw
Ilex latifolia Lusterleaf holly
Ilex pedunculosa Long stalk holly
Ilex vomitoria Yaupon holly
Ilex x ‘Emily Bruner’ Emily Bruner holly
Ilex x ‘Mary Nell’ Mary Nell holly
Ilex x 'Nellie R. Stevens' Nellie R. Stevens holly
Ilex x attenuata Savannah, Foster, Sunny Foster, East Palatka
Ilex x koehneana Koehne holly
Juniperus scopulorum Rocky Mountain juniper: Blue Haven, Skyrocket, Wichita Blue,
Juniperus virginiana cvs. Blue Mountain, Hillii, Canaertii
Juniperus chinensis Chinese juniper: Wintergreen, Spartan, Hooks
Koelreuteria bipinnata Goldenraintree
Koelreuteria paniculata Goldenraintree
Lagerstroemia fauriei Japanese crapemyrtle
Lagerstroemia indica Crapemyrtle
Lagerstroemia indica x fauriei Choctaw, Muskogee, Natchez, Tuscarora
Lithocarpus henryi Henry tanbark oak
Ilex vomitoria 'Pendula' Weeping yaupon holly
Maackia amurensis Amur Maackia
Magnolia grandiflora ‘Little Gem’ Little Gem magnolia
Magnolia hybrids Ann, Betty, Judy, Mary Nell, Galaxy
Malus hybrids David, Harvest Gold, Indian Summer, Callaway Malus spp. Crabapple
Morus australis ‘Unryo’ Contorted mulberry
Ostrya virginiana American hophornbeam or ironwood
Oxydendrum arboreum Sourwood
Parrotia persica Persian ironwood
Persea borbonia Redbay
Photinia serrulata Chinese photinia
Picea glauca (dwarf cultivars) Conica
Picea pungens (dwarf cultivars) Bakeri, Fat Albert, Foxtail
Pinus mugo Mugo pine
Pinus nigra cvs. Arnold Sentinel, Monstrosa
Pinus rigida Sherman Eddy
Pinus strobus cvs.
Pinus thunbergiana cvs.
Pistacia chinensis Chinese pistache
Poncirus trifoliata Hardy orange
Ptelea trifoliata Hop tree
Rhamnus caroliniana Carolina buckthorn
Rhus typhina Staghorn sumac
Trachycarpus fortunei Windmill palm
Ulmus glabra ‘Horizontalis’ Tabletop Scotch elm
Vitex agnus-castus Chastetree; vitex
Ziziphus jujuba Common jujuba
Installing smaller trees 2 in. (5 cm) or less caliper for deciduous trees and 6 feet (1.8 m) or less height for evergreen trees, reduces the monetary investment and increases the survival rate of installation during drought periods. Installing smaller trees allows the tree to establish more quickly than installing a large tree and will require less maintenance over time.
- Installing trees during times of drought and water restrictions should only be done with caution and if there is a persuasive need. An understanding of the risks and consideration of proper maintenance activities necessary to establish trees during these periods is crucial.
- Install trees to replace drought stressed and dead trees, which can help reduce the negative effects of drought on the landscape by lowering the heat and solar radiation reaching the soil.
- Keeping trees in the landscape helps reduce soil erosion, by stabilizing soils and intercepting rainfall.
- Trees also significantly reduce storm water runoff and provide shade for landscapes and structures to help minimize water and energy use.
- Factors to consider when installing trees and shrubs include soil conditions, available space above and below ground, exposure, moisture, and light requirements.
- Select trees from species that are hardy to the region and fit well with the xeriscape principles of maintaining an attractive landscape with minimal water use.
- Proper mulching and adherence to watering guidelines for trees and shrubs will help establish newly installed trees in times of drought.
Why Plant Trees During a Drought?
Installing trees and shrubs during drought can be risky. If watering restrictions are in place, establishing trees in a semi-arid region may be difficult enough without an extended drought to contend with. However, by eliminating all tree plantings, opportunities to sustain the urban forest may be missed. It is critical to not only have diversity of species in the landscape but also a diversity of age among those species in the landscape. This means installing new and replacement trees each year, even during times of drought, to replace trees that will be lost to age, injury, drought, and other causes.
Carefully installed trees continues to maintain soil stability, reduce soil erosion, control and utilize storm water runoff, shade moisture-starved lawns and reduce energy usage by shading homes in summer and blocking winds in winter. A well-stocked urban forest also acts as an air filter and purifier, absorbing carbon dioxide and emitting oxygen to help provide cleaner air.
Some plants are more tolerant of drought stress. This may be attributed to an aggressive, deep root system or thickened, waxy leaves. Drought tolerance may also be attributed to physiological responses within the plant.
Large Drought Tolerant Trees
Scientific Name Common Name
Acer leucoderme Chalkbark maple
Acer platanoides Norway maple
Acer pseudoplatanus Sycamore maple
Acer rubrum Red maple
Acer x freemanii Freeman maple
Alnus glutinosa Common alder
Betula lenta Sweet birch
Calocedrus decurrens Incense cedar
Carpinus betulus European hornbeam
Carya illinoensis Pecan
Castanea sativa Spanish chestnut
Catalpa speciosa Northern catalpa
Cedrus atlantica 'Glauca' Blue atlas cedar
Cedrus deodara Deodar cedar
Cedrus libani Cedar of Lebanon
Celtis laevigata Hackberry
Celtis occidentalis Hackberry
Cladrastis kentuckea Yellowwood
Cryptomeria japonica
Cryptomeria Cunninghamia lanceolata China fir
Cupressus arizonica Arizona cypress
Eucommia ulmoides Hardy rubber tree
Fraxinus americana White ash (in non-EAB infested areas)
Fraxinus pennsylvanica Green ash (in non-EAB infested areas)
Ginkgo biloba (male) Ginkgo
Gleditsia triacanthos Honeylocust
Gleditsia triacanthos inermis Thornless honeylocust
Gymnocladus dioicus Kentucky coffeetree
Ilex opaca American holly
Juniperus saliciola Southern red cedar
Juniperus virginiana Eastern red cedar
Kalopanax pictus Castor-aralia
Liquidambar styraciflua Sweetgum
Maclura pomifera Osage-orange
Magnolia grandiflora Southern magnolia
Metasequoia stroboscopes Dawn redwood
Nyssa ogeche Ogeche gum
Oxydendrum arboreum Sourwood
Phellodendron amurense Amur cork tree
Picea glauca Alberta spruce
Picea pungens Colorado blue spruce
Pinus bungeana Lacebark pine
Pinus cembra Swiss stone pine
Pinus echinata Shortleaf pine
Pinus elliottii Slash pine
Pinus flexilis Limber pine
Pinus heldreichii Bosnian pine
Pinus koraiensis Korean pine
Pinus mugo Mugo pine
Pinus nigra Austrian pine
Pinus rigida Pitch pine
Pinus sylvestris Scotch pine
Pinus taeda Loblolly pine
Pinus thunbergiana Japanese black pine
Pinus virginiana Virginia pine P
inus wallichiana Himalayan pine
Platanus acerifolia London plane tree
Pyrus calleryana cvs. Cleveland, Aristocrat, Capital, New Bradford, Redspire
Quercus acutissima Sawtooth oak
Quercus alba White oak
Quercus bicolor Swamp white oak
Quercus coccinea Scarlet oak
Quercus falcata Southern red oak
Quercus hemisphaerica Darlington oak
Quercus imbricaria Shingle oak
Quercus lyrata Overcup oak
Quercus macrocarpa Bur oak
Quercus nigra Water oak
Quercus nuttalii Nuttall oak
Quercus palustris Pin oak
Quercus phellos Willow oak
Quercus prinus Chestnut oak
Quercus rubra Red oak
Quercus shumardii Shumard oak
Quercus stellata Post oak
Quercus virginiana Live oak
Robinia pseudoacacia Black locust
Sassafras albidum Sassafras
Taxodium ascendens Pond cypress
Taxodium distichum Baldcypress
Tilia americana American linden
Tilia cordata Littleleaf linden
Tilia tomentosa Silver linden
Ulmus alata Winged elm
Ulmus americana cvs. Liberty, Valley Forge Ulmus parvifolia Lacebark elm
Zelkova serrata Zelkova
Small Drought Tolerant Trees
Scientific Name Common Name
Acer barbatum Southern sugar maple
A. saccharum ssp. floridanum
Acer buergeranum Trident maple
Acer campestre Hedge maple
Acer ginnala Amur maple
Acer leucoderme Whitebark maple, calk maple
Acer negundo Boxelder
Acer truncatum Purple blow maple
Aesculus californica California buckeye
Aesculus pavia Red buckeye
Albizia julibrissin Mimosa
Alnus japonica Japanese alder
Alnus serrulata Tag alder
Carpinus betulus European Hornbeam
Carpinus betulus fastigiata Upright European hornbeam
Carpinus caroliniana American hornbeam, Ironwood
Carpinus japonica Japanese hornbeam
Carpinus orientalis Oriental hornbeam
Cercis canadensis Eastern redbud
Cercis canadensis ssp retisus Oklahoma redbud
Cercis canadensis ssp. texensis Texas redbud
Cercis chinensis Chinese redbud
Chionanthus retusus Chinese fringe tree
Cornus mas Cornelian cherry dogwood
Cotinus coggygria Smoketree
Cotinus hybrids Grace
Cotinus obovatus American smoke tree
Crataegus crus-galli Cockspur hawthorn
Crataegus laevigata Scarlet hawthorn, English hawthorn
Crataegus phaenopyrum Washington hawthorn
Crataegus x lavallei Lavalle hawthorn
Crataegus viridis Green hawthorn
Cupressus sempervirens Italian cypress
Cydonia sinensis Chinese quince
Cupressus arizonica cvs. Arizona cypress
Elaeagnus angustifolia Russian olive
Euscaphis japonica Korean sweetheart tree
Heptacodium miconiodes Seven-son flower
Hovenia dulcis Japanese raisin tree
Ilex ‘China Boy’, ‘China Girl’ China holly
Ilex cassine Dahoon holly
Ilex cornuta cvs. Burfordii, D’Or, O’ Spring
Ilex decidua Possumhaw
Ilex latifolia Lusterleaf holly
Ilex pedunculosa Long stalk holly
Ilex vomitoria Yaupon holly
Ilex x ‘Emily Bruner’ Emily Bruner holly
Ilex x ‘Mary Nell’ Mary Nell holly
Ilex x 'Nellie R. Stevens' Nellie R. Stevens holly
Ilex x attenuata Savannah, Foster, Sunny Foster, East Palatka
Ilex x koehneana Koehne holly
Juniperus scopulorum Rocky Mountain juniper: Blue Haven, Skyrocket, Wichita Blue,
Juniperus virginiana cvs. Blue Mountain, Hillii, Canaertii
Juniperus chinensis Chinese juniper: Wintergreen, Spartan, Hooks
Koelreuteria bipinnata Goldenraintree
Koelreuteria paniculata Goldenraintree
Lagerstroemia fauriei Japanese crapemyrtle
Lagerstroemia indica Crapemyrtle
Lagerstroemia indica x fauriei Choctaw, Muskogee, Natchez, Tuscarora
Lithocarpus henryi Henry tanbark oak
Ilex vomitoria 'Pendula' Weeping yaupon holly
Maackia amurensis Amur Maackia
Magnolia grandiflora ‘Little Gem’ Little Gem magnolia
Magnolia hybrids Ann, Betty, Judy, Mary Nell, Galaxy
Malus hybrids David, Harvest Gold, Indian Summer, Callaway Malus spp. Crabapple
Morus australis ‘Unryo’ Contorted mulberry
Ostrya virginiana American hophornbeam or ironwood
Oxydendrum arboreum Sourwood
Parrotia persica Persian ironwood
Persea borbonia Redbay
Photinia serrulata Chinese photinia
Picea glauca (dwarf cultivars) Conica
Picea pungens (dwarf cultivars) Bakeri, Fat Albert, Foxtail
Pinus mugo Mugo pine
Pinus nigra cvs. Arnold Sentinel, Monstrosa
Pinus rigida Sherman Eddy
Pinus strobus cvs.
Pinus thunbergiana cvs.
Pistacia chinensis Chinese pistache
Poncirus trifoliata Hardy orange
Ptelea trifoliata Hop tree
Rhamnus caroliniana Carolina buckthorn
Rhus typhina Staghorn sumac
Trachycarpus fortunei Windmill palm
Ulmus glabra ‘Horizontalis’ Tabletop Scotch elm
Vitex agnus-castus Chastetree; vitex
Ziziphus jujuba Common jujuba
Heat Tolerant Trees
There are several species of trees that will tolerate heat, but there are now many new cultivars or introductions that have been selected for their heat tolerance in addition to other desirable features. Keep in mind that although these trees are heat tolerant, that does not mean that they are also resistant to disease and pest problems or other abiotic conditions. So when you are selecting a tree for planting, make sure you plant the right tree in the right spot, for the right reason.
Heat Tolerant Species
The following is a list of species that are tolerant of urban heat.
Botanical Name Trade Name Hardiness Zone Heat Zone Photo
Acer buergerianum Trident Maple 5 – 9 9 - 5 Photo
Acer campestre Hedge Maple 5 – 8* 8 - 4 Photo
Acer rubrum Red Maple 3 – 9 8 - 1 Photo
Catalpa speciosa Catalpa 4 – 8 8 - 1 Photo
Cedrus spp. Cedar 5 – 9* 9 - 6 Photo
Celtis occidentalis Hackberry 2 – 9 9 - 1 Photo
Cryptomeria japonica Japanese Cryptomeria 5 – 9 9 - 4 Photo
Eucommia ulmoides Hardy Rubber Tree 4 – 7 7 - 1 Photo
Ginkgo biloba Ginkgo – male cultivars 3 – 9 9 - 3 Photo
Juniperus virginiana Eastern Redcedar 2 – 9 9 - 1 Photo
Lagerstroemia spp. Crape Myrtle 7 – 9* 12 - 9 Photo
Pinus spp. Pine 2 – 9* 8 - 1 Photo
Pistacia chinensis Chinese Pistache 6 – 9 9 - 6 Photo
Quercus acutissima Sawtooth Oak 5 – 9 8 - 1 Photo
Quercus phellos Willow Oak 5 – 9 9 - 3 Photo
Quercus rubra Red Oak 4 – 8 9 - 5 Photo
Sophora japonica Japanese Pagodatree 4 – 8 9 - 5 Photo
Tilia cordata Littleleaf Linden 3 – 7 8 - 1 Photo
Tilia tomentosa Silver Linden 4 – 7 9 - 1 Photo
Ulmus parvifolia Lacebark Elm 4 – 9 9 - 1 Photo
Zelkova serrata Japanese Zelkova 5 – 8 9 - 5 Photo
* Zone range depends on the species selected, as some are more heat tolerant than others.
Heat Tolerant Cultivars
This second list contains heat tolerant cultivars selected from species that are not noted for being heat tolerant. These cultivars were selected for their excellent tolerance to heat within the climatic range of the species.
Botanical Name Trade Name Hardiness Zone Heat Zone Photo
Acer ginnala 'JFS-UGA' Red November™ Maple 2 – 8 7 – 1 Photo
Acer saccharum 'Autumn Splendor' Autumn Splendor Sugar Maple 5 – 9 8 – 1 Photo
A. s. ‘Bailsta’ Fall Fiesta® Sugar Maple 4 – 8 8 – 1 Photo
A. s. ‘Green Mountain’ Green Mountain® Sugar Maple 4 – 8 8 – 1 Photo
A. s. ‘JFS-Caddo2’ Flashfire® Sugar Maple 5 – 9 8 – 1 Photo
A. s. 'John Pair' John Pair Sugar Maple 5 – 9 8 – 1 Photo
A. s. ‘Legacy’ Legacy’® Sugar Maple 4 – 8 8 – 1 Photo
A. s. 'Morton' Crescendo™ Sugar Maple 5 – 9 8 – 1 Photo
A. s. 'Reba' Belle Tower™ Sugar Maple 5 – 8 8 – 1 Photo
Acer x freemanii 'Jeffersred' Autumn Blaze® Maple 3 – 8 8 – 1 Photo
Acer truncatum x plat. ‘JFS-KW202’ Crimson Sunset® Maple 4 – 8 8 – 1 Photo
Ulmus propinqua 'JFS-Bieberich Emerald Sunshine Elm 5 – 9 9 – 1 Photo
** non-EAB areas only
There are several species of trees that will tolerate heat, but there are now many new cultivars or introductions that have been selected for their heat tolerance in addition to other desirable features. Keep in mind that although these trees are heat tolerant, that does not mean that they are also resistant to disease and pest problems or other abiotic conditions. So when you are selecting a tree for planting, make sure you plant the right tree in the right spot, for the right reason.
Heat Tolerant Species
The following is a list of species that are tolerant of urban heat.
Botanical Name Trade Name Hardiness Zone Heat Zone Photo
Acer buergerianum Trident Maple 5 – 9 9 - 5 Photo
Acer campestre Hedge Maple 5 – 8* 8 - 4 Photo
Acer rubrum Red Maple 3 – 9 8 - 1 Photo
Catalpa speciosa Catalpa 4 – 8 8 - 1 Photo
Cedrus spp. Cedar 5 – 9* 9 - 6 Photo
Celtis occidentalis Hackberry 2 – 9 9 - 1 Photo
Cryptomeria japonica Japanese Cryptomeria 5 – 9 9 - 4 Photo
Eucommia ulmoides Hardy Rubber Tree 4 – 7 7 - 1 Photo
Ginkgo biloba Ginkgo – male cultivars 3 – 9 9 - 3 Photo
Juniperus virginiana Eastern Redcedar 2 – 9 9 - 1 Photo
Lagerstroemia spp. Crape Myrtle 7 – 9* 12 - 9 Photo
Pinus spp. Pine 2 – 9* 8 - 1 Photo
Pistacia chinensis Chinese Pistache 6 – 9 9 - 6 Photo
Quercus acutissima Sawtooth Oak 5 – 9 8 - 1 Photo
Quercus phellos Willow Oak 5 – 9 9 - 3 Photo
Quercus rubra Red Oak 4 – 8 9 - 5 Photo
Sophora japonica Japanese Pagodatree 4 – 8 9 - 5 Photo
Tilia cordata Littleleaf Linden 3 – 7 8 - 1 Photo
Tilia tomentosa Silver Linden 4 – 7 9 - 1 Photo
Ulmus parvifolia Lacebark Elm 4 – 9 9 - 1 Photo
Zelkova serrata Japanese Zelkova 5 – 8 9 - 5 Photo
* Zone range depends on the species selected, as some are more heat tolerant than others.
Heat Tolerant Cultivars
This second list contains heat tolerant cultivars selected from species that are not noted for being heat tolerant. These cultivars were selected for their excellent tolerance to heat within the climatic range of the species.
Botanical Name Trade Name Hardiness Zone Heat Zone Photo
Acer ginnala 'JFS-UGA' Red November™ Maple 2 – 8 7 – 1 Photo
Acer saccharum 'Autumn Splendor' Autumn Splendor Sugar Maple 5 – 9 8 – 1 Photo
A. s. ‘Bailsta’ Fall Fiesta® Sugar Maple 4 – 8 8 – 1 Photo
A. s. ‘Green Mountain’ Green Mountain® Sugar Maple 4 – 8 8 – 1 Photo
A. s. ‘JFS-Caddo2’ Flashfire® Sugar Maple 5 – 9 8 – 1 Photo
A. s. 'John Pair' John Pair Sugar Maple 5 – 9 8 – 1 Photo
A. s. ‘Legacy’ Legacy’® Sugar Maple 4 – 8 8 – 1 Photo
A. s. 'Morton' Crescendo™ Sugar Maple 5 – 9 8 – 1 Photo
A. s. 'Reba' Belle Tower™ Sugar Maple 5 – 8 8 – 1 Photo
Acer x freemanii 'Jeffersred' Autumn Blaze® Maple 3 – 8 8 – 1 Photo
Acer truncatum x plat. ‘JFS-KW202’ Crimson Sunset® Maple 4 – 8 8 – 1 Photo
Ulmus propinqua 'JFS-Bieberich Emerald Sunshine Elm 5 – 9 9 – 1 Photo
** non-EAB areas only
Trees that Survive Landslides
Research on the relationship between forests and landslides indicates that tree roots reduce the risk of landslides. This is because during periods of heavy rainfall, the force created by water flow contributes to soil movement. However, soil stabilization is enhanced by tree roots forming anchors and networks to slow down erosion and landslides. Trees also modify the soil moisture regime through increased evapotranspiration.
Landslides occur on sloping land. Installing trees on this land to prevent landslides may be done at the top of the slope as well as along the slope itself. In planning for plantings, spacing of no more than 25 feet (7 m) apart is needed for the development of the overlapping root networks that provide soil cohesion across an area. If the soil or growing conditions of the site are not uniform, then closer spacing is essential to provide root networks despite the poor growing conditions. In addition to tree density, the extent of root cohesion is dependent upon the species uniformity at a site because root cohesion within a stand of trees is much more effective with the same species that will link roots together and share soil space.
Rooting characteristics are a critical aspect to consider during species selection for tree installations needed to reduce the risk of landslides in urban areas where soil conditions are probably extremely poor. Because deep or tap root trees produce more depth in the root cohesion network, tap root trees should be preferred for installation to reduce the risk of landslides. Installing tap rooted trees however is a challenge for arborists and landscape architects because traditional methods of transplanting do not accommodate tap roots.
A study of landslide covered slopes showed that saplings of the tap root system species, such as the following could stabilize soil as thick as 3 feet (1 m):
Trident Maple (Acer buergerianum),
American Smoketree (Cotinus obovatus),
Hawthorn (Crataegus spp.),
Hornbeam (Carpinus spp.),
Hackberry (Celtis spp.),
Turkish Filbert (Corylus colurna),
Tuliptree (Liriodendron tulipifera),
Black Tupelo (Nyssa sylvatica),
American Hophornbeam (Ostrya virginiana),
most oak varieties (Quercus spp.).
Most other trees such as sugar maple saplings with a lateral root system seldom stabilize soil thicker than 20 inches (0.5 m). Tap roots provide greater depth for anchoring the root network; however, tap roots of both broadleaf and conifer species lose importance in regard to tree stability relative to the spread of lateral roots as a tree ages.
Consideration must be given to site conditions such as soil depth, bedrock geology, and water table elevation to increase the likelihood of tree installation success. When feasible, modifications of a site to reduce the limiting conditions should be done to enhance tree growth and stabilize landslide-prone urban areas.
Selection of Trees for New Installations
Selection of species for plantings and retention of existing trees in landslide-prone urban areas is important to urban forest management and gives rise to research questions in regard to urban tree species and landslides. Based upon the results of this research at locations where landslides have occurred, certain species were classified as having deep roots and are recommended for landslide prevention. These trees below plus those mentioned above, and trees growing from seeds planted on the site are the best for landslide prone areas:
blue atlas cedar (Cedrus atlantica ‘Glauca’),
deodar cedar (Cedrus deodara ),
eastern redbud (Cercis canadensis),
ash (Fraxinus spp.), (in non EAB susceptible areas)
ginkgo (Ginkgo biloba),
Kentucky Coffee Tree (Gymnocladius dioicus),
hybrid crepe myrtles (Lagerstroemia indica X fauriei),
saucer magnolia (Magnolia soulangiana),
Canary Island pine (Pinus canariensis),
Chinese pistache (Pistacia chinensis),
hybrid chitalpa (Salix X Chitalpa),
Not Suitable
Based upon the results of research at locations where landslides have occurred, certain species were classified as having surface root systems and therefore should not be installed where there is the potential for future landslides. These trees include:
red maple (Acer rubrum),
sugar maple (Acer saccharum),
common hackberry (Celtis occidentalis),
sugarberry (Celtis laevigata),
willow (Salix spp.).
Urban trees are not affected differently by landslides in regard to species, soil type, slope steepness, or root system type, but saplings are lost much less frequently than large trees. Management of urban areas with landslide potential should be based on landslide history to identify locales of special concern and to prioritize sites for tree installations since a landslide recurrence at a site is unlikely for decades, or at least until a sufficient mass of potential landslide soil redevelops.
Research on the relationship between forests and landslides indicates that tree roots reduce the risk of landslides. This is because during periods of heavy rainfall, the force created by water flow contributes to soil movement. However, soil stabilization is enhanced by tree roots forming anchors and networks to slow down erosion and landslides. Trees also modify the soil moisture regime through increased evapotranspiration.
Landslides occur on sloping land. Installing trees on this land to prevent landslides may be done at the top of the slope as well as along the slope itself. In planning for plantings, spacing of no more than 25 feet (7 m) apart is needed for the development of the overlapping root networks that provide soil cohesion across an area. If the soil or growing conditions of the site are not uniform, then closer spacing is essential to provide root networks despite the poor growing conditions. In addition to tree density, the extent of root cohesion is dependent upon the species uniformity at a site because root cohesion within a stand of trees is much more effective with the same species that will link roots together and share soil space.
Rooting characteristics are a critical aspect to consider during species selection for tree installations needed to reduce the risk of landslides in urban areas where soil conditions are probably extremely poor. Because deep or tap root trees produce more depth in the root cohesion network, tap root trees should be preferred for installation to reduce the risk of landslides. Installing tap rooted trees however is a challenge for arborists and landscape architects because traditional methods of transplanting do not accommodate tap roots.
A study of landslide covered slopes showed that saplings of the tap root system species, such as the following could stabilize soil as thick as 3 feet (1 m):
Trident Maple (Acer buergerianum),
American Smoketree (Cotinus obovatus),
Hawthorn (Crataegus spp.),
Hornbeam (Carpinus spp.),
Hackberry (Celtis spp.),
Turkish Filbert (Corylus colurna),
Tuliptree (Liriodendron tulipifera),
Black Tupelo (Nyssa sylvatica),
American Hophornbeam (Ostrya virginiana),
most oak varieties (Quercus spp.).
Most other trees such as sugar maple saplings with a lateral root system seldom stabilize soil thicker than 20 inches (0.5 m). Tap roots provide greater depth for anchoring the root network; however, tap roots of both broadleaf and conifer species lose importance in regard to tree stability relative to the spread of lateral roots as a tree ages.
Consideration must be given to site conditions such as soil depth, bedrock geology, and water table elevation to increase the likelihood of tree installation success. When feasible, modifications of a site to reduce the limiting conditions should be done to enhance tree growth and stabilize landslide-prone urban areas.
Selection of Trees for New Installations
Selection of species for plantings and retention of existing trees in landslide-prone urban areas is important to urban forest management and gives rise to research questions in regard to urban tree species and landslides. Based upon the results of this research at locations where landslides have occurred, certain species were classified as having deep roots and are recommended for landslide prevention. These trees below plus those mentioned above, and trees growing from seeds planted on the site are the best for landslide prone areas:
blue atlas cedar (Cedrus atlantica ‘Glauca’),
deodar cedar (Cedrus deodara ),
eastern redbud (Cercis canadensis),
ash (Fraxinus spp.), (in non EAB susceptible areas)
ginkgo (Ginkgo biloba),
Kentucky Coffee Tree (Gymnocladius dioicus),
hybrid crepe myrtles (Lagerstroemia indica X fauriei),
saucer magnolia (Magnolia soulangiana),
Canary Island pine (Pinus canariensis),
Chinese pistache (Pistacia chinensis),
hybrid chitalpa (Salix X Chitalpa),
Not Suitable
Based upon the results of research at locations where landslides have occurred, certain species were classified as having surface root systems and therefore should not be installed where there is the potential for future landslides. These trees include:
red maple (Acer rubrum),
sugar maple (Acer saccharum),
common hackberry (Celtis occidentalis),
sugarberry (Celtis laevigata),
willow (Salix spp.).
Urban trees are not affected differently by landslides in regard to species, soil type, slope steepness, or root system type, but saplings are lost much less frequently than large trees. Management of urban areas with landslide potential should be based on landslide history to identify locales of special concern and to prioritize sites for tree installations since a landslide recurrence at a site is unlikely for decades, or at least until a sufficient mass of potential landslide soil redevelops.
Trees that Resist Wildfires
Finding trees that resist wildfires is a challenge because trees are composed of wood that readily burns. Fortunately, some trees have actually adapted themselves to be protected against forest fires. A new study has found that trees worldwide develop thicker bark when they live in fire-prone areas. These trees are called "pyrophytes," which means fire-traited plants. Bark protects the inside of the trunk from overheating and is one of a handful of adaptations that trees use to survive fire. Other trees bear seed cones called "serotinous cones." These cones have seeds inside that are opened only by the intense heat of a wildfire. A serotinous cone, such as that of the lodgepole pine, can contain enough seeds to cover the forest with lots of seeds.
Some plants are more flammable than others. Evergreen conifers, such as juniper, pine, spruce, and cedar, are high in resins and waxes, the properties that keep them evergreen and durable. Unfortunately for each of these trees, the resins and waxes are highly flammable.
Fire Prevention Around Homes
The top priority of a fire-dissuading landscape is to create a “defendable space”. This is an area that will serve as a buffer zone should a wildfire approach a home. The goal is to keep a fire moving “slow and low” until it can be extinguished.
Highly flammable plant varieties should be removed from around a home. Replace them with deciduous plants. Deciduous plants retain more water in their foliage, which makes them much more difficult to ignite and burn. However, they also drop their foliage during the winter months and the dead leaves left on the ground may dry into a significant amount of combustible material. Picking up and composting or discarding freshly fallen leaves removes a source of ignition from around a home.
Avoid “ladder fuels”. An example of this is a burning, dry, ornamental grass where the ground fire, climbs up the tall leaves of the ornamental grass and that ignites a taller shrub that allows the flames to jump up to some pine branches, which then jumps up to the roof. The goal of a fire wise landscape is to hold the fire on the ground and out of a tree's canopy.
Ideally, garden designs should also consist of islands in the yard with an interesting plant mix and hardscapes separating one garden from the next. The hardscape can be a driveway, patio or rock lawn. This technique also allows firefighters some precious space between gardens should they have to fight the flames.
There are also measures that an arborist and landscape architect can take to install trees in a manner that will minimize the damage that might occur during a wildfire. For example:
The overall goal is to keep in mind that all trees are flammable under certain conditions. Care should be taken to lessen factors that contribute to their flammability and risk.
Developing lists of trees that resist wildfires have been prepared by twenty state Cooperative Extension Service offices around the U.S. The following list from Maryland seems pretty typical. These sources are science-based, consistent with Firewise principles, and are updated periodically.
Trees that Resist Wildfires
Scientific Name Common Name
Acer palmatum Japanese Maple
Acer rubrum Red Maple
Acer saccharinum Silver/River Maple
Acer saccharum Sugar Maple
Acer spicatum Mountain Maple
Adansonia sp. Baobab Tree
Aesculus hippocastanum Horsechestnut
Amelanchier canadensis Shadbush / Serviceberry
Betula nigra River birch
Betula papyrifera Paper/White Birch
Carpinus caroliniana Hornbeam
Carya illinoiensis Pecan
Carya tomentosa Mockernut Hickory
Castanea mollissima Chinese Chestnut
Celtis occidentalis Common Hackberry
Cercis canadensis Eastern Redbud
Chionanthus virginicus Fringetree
Cladrastis kentuckea Yellowwood
Cornus florida Flowering Dogwood
Cornus kousa Kousa/Chinese Dogwood
Crataegus spp. Hawthorn
Diospyros virginiana Persimmon
Eucalyptus sp. Eucalyptus
Fagus grandifolia American Beech
Fraxinus americana White Ash
Fraxinus pennsylvanica Green Ash
Ginkgo biloba Ginkgo Maidenhair Tree
Gleditsia triancanthos var. inermis Thornless Honeylocust
Gymnocladus dioicus Kentucky Coffeetree
Halesia carolina Carolina Silverbell
Juglans nigra Black Walnut
Liquidambar styraciflua Sweetgum
Liriodendron tulipifera Yellow Poplar, Tulip Poplar, Tulip Tree
Magnolia acuminata Cucumber Magnolia
Magnolia grandiflora Southern Magnolia or bull bay
Magnolia virginiana Sweetbay Magnolia
Malus spp. Apples & Crabapples
Nyssa sylvatica Black Gum, Black Tupelo, Sour Gum
Oxydendrum arboreum Sourwood, Sorrel Tree
Pinus banksiana Jack Pine
Pinus ponderosa Ponderosa Pine
Pistacia chinensis Chinese Pistache
Platanus x acerifolia London Planetree
Populus grandidentata Big-Toothed Aspen
Prunus serotina Black Cherry
Prunus subhirtella Weeping/Rosebud Cherry
Pyrus communis Common Pear
Quercus agrifolia Coast Live Oak
Quercus alba White Oak
Quercus bicolor Swamp White Oak
Quercus coccinea Scarlet Oak
Quercus macrocarpa Bur Oak
Quercus palustris Pin Oak
Quercus rubra Northern Red Oak
Salix babylonica Weeping Willow
Salix nigra Black Willow
Sequoiadendron giganteum Giant Sequoia
Sorbus americana American Mountain-ash
Tilia cordata Littleleaf Linden
Ulmus americana American Elm
Ulmus davidiana var. japonica Japanese Elm
Viburnum prunifolium Blackhaw Viburnum
Zelkova serrata Japanese Zelkova
Note: One tree that is noted for its resistance to wildfires is Sequoia sempervirens, Coast Redwood. This tree has bark that is up to one foot thick and contains no flammable resins. If damaged by fire, a redwood will readily sprout new branches or even an entirely new crown, and if the parent tree is killed, new buds will sprout from its base. Fires, moreover, appear to actually benefit redwoods by causing substantial mortality in competing species while having only minor effects on redwood. Burned areas are favorable to the successful germination of redwood seeds. Unfortunately, coast redwoods grow best in the foggy regions of coastal California and southern Oregon and not in fire prone areas.
Sources
The test that follows contains 80 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award 4.0 CEUs* for a passing grade. SAF members will earn 1.0 Cat. 1-CT credit for a passing grade. The cost for taking this test is $20 per credit. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 4.0 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, or BCMA science credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA and MTOA members may submit your ISA certification record to these organizations and receive credits one for one.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant / gibneyCE.com’. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website. *SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Finding trees that resist wildfires is a challenge because trees are composed of wood that readily burns. Fortunately, some trees have actually adapted themselves to be protected against forest fires. A new study has found that trees worldwide develop thicker bark when they live in fire-prone areas. These trees are called "pyrophytes," which means fire-traited plants. Bark protects the inside of the trunk from overheating and is one of a handful of adaptations that trees use to survive fire. Other trees bear seed cones called "serotinous cones." These cones have seeds inside that are opened only by the intense heat of a wildfire. A serotinous cone, such as that of the lodgepole pine, can contain enough seeds to cover the forest with lots of seeds.
Some plants are more flammable than others. Evergreen conifers, such as juniper, pine, spruce, and cedar, are high in resins and waxes, the properties that keep them evergreen and durable. Unfortunately for each of these trees, the resins and waxes are highly flammable.
Fire Prevention Around Homes
The top priority of a fire-dissuading landscape is to create a “defendable space”. This is an area that will serve as a buffer zone should a wildfire approach a home. The goal is to keep a fire moving “slow and low” until it can be extinguished.
Highly flammable plant varieties should be removed from around a home. Replace them with deciduous plants. Deciduous plants retain more water in their foliage, which makes them much more difficult to ignite and burn. However, they also drop their foliage during the winter months and the dead leaves left on the ground may dry into a significant amount of combustible material. Picking up and composting or discarding freshly fallen leaves removes a source of ignition from around a home.
Avoid “ladder fuels”. An example of this is a burning, dry, ornamental grass where the ground fire, climbs up the tall leaves of the ornamental grass and that ignites a taller shrub that allows the flames to jump up to some pine branches, which then jumps up to the roof. The goal of a fire wise landscape is to hold the fire on the ground and out of a tree's canopy.
Ideally, garden designs should also consist of islands in the yard with an interesting plant mix and hardscapes separating one garden from the next. The hardscape can be a driveway, patio or rock lawn. This technique also allows firefighters some precious space between gardens should they have to fight the flames.
There are also measures that an arborist and landscape architect can take to install trees in a manner that will minimize the damage that might occur during a wildfire. For example:
- Install trees that have a low surface area to volume ratio, such as plants with thick, broad leaves instead of those with narrow, needle-like leaves.
- Select trees that have a high moisture content, as found in succulents and other plants with fleshy foliage.
- Select trees that will have a low percentage of dead matter or debris in their crowns and keep the forest floor clear of unnecessary flammable material.
- Select trees that are drought tolerant or keep them irrigated so they do not have a low moisture content especially when the likelihood of a wildfire is high.
- Select trees that grow well in the local climate and soil type.
- Select trees with an open, loose branching habit so the fire can not jump from one branch to the next.
The overall goal is to keep in mind that all trees are flammable under certain conditions. Care should be taken to lessen factors that contribute to their flammability and risk.
Developing lists of trees that resist wildfires have been prepared by twenty state Cooperative Extension Service offices around the U.S. The following list from Maryland seems pretty typical. These sources are science-based, consistent with Firewise principles, and are updated periodically.
Trees that Resist Wildfires
Scientific Name Common Name
Acer palmatum Japanese Maple
Acer rubrum Red Maple
Acer saccharinum Silver/River Maple
Acer saccharum Sugar Maple
Acer spicatum Mountain Maple
Adansonia sp. Baobab Tree
Aesculus hippocastanum Horsechestnut
Amelanchier canadensis Shadbush / Serviceberry
Betula nigra River birch
Betula papyrifera Paper/White Birch
Carpinus caroliniana Hornbeam
Carya illinoiensis Pecan
Carya tomentosa Mockernut Hickory
Castanea mollissima Chinese Chestnut
Celtis occidentalis Common Hackberry
Cercis canadensis Eastern Redbud
Chionanthus virginicus Fringetree
Cladrastis kentuckea Yellowwood
Cornus florida Flowering Dogwood
Cornus kousa Kousa/Chinese Dogwood
Crataegus spp. Hawthorn
Diospyros virginiana Persimmon
Eucalyptus sp. Eucalyptus
Fagus grandifolia American Beech
Fraxinus americana White Ash
Fraxinus pennsylvanica Green Ash
Ginkgo biloba Ginkgo Maidenhair Tree
Gleditsia triancanthos var. inermis Thornless Honeylocust
Gymnocladus dioicus Kentucky Coffeetree
Halesia carolina Carolina Silverbell
Juglans nigra Black Walnut
Liquidambar styraciflua Sweetgum
Liriodendron tulipifera Yellow Poplar, Tulip Poplar, Tulip Tree
Magnolia acuminata Cucumber Magnolia
Magnolia grandiflora Southern Magnolia or bull bay
Magnolia virginiana Sweetbay Magnolia
Malus spp. Apples & Crabapples
Nyssa sylvatica Black Gum, Black Tupelo, Sour Gum
Oxydendrum arboreum Sourwood, Sorrel Tree
Pinus banksiana Jack Pine
Pinus ponderosa Ponderosa Pine
Pistacia chinensis Chinese Pistache
Platanus x acerifolia London Planetree
Populus grandidentata Big-Toothed Aspen
Prunus serotina Black Cherry
Prunus subhirtella Weeping/Rosebud Cherry
Pyrus communis Common Pear
Quercus agrifolia Coast Live Oak
Quercus alba White Oak
Quercus bicolor Swamp White Oak
Quercus coccinea Scarlet Oak
Quercus macrocarpa Bur Oak
Quercus palustris Pin Oak
Quercus rubra Northern Red Oak
Salix babylonica Weeping Willow
Salix nigra Black Willow
Sequoiadendron giganteum Giant Sequoia
Sorbus americana American Mountain-ash
Tilia cordata Littleleaf Linden
Ulmus americana American Elm
Ulmus davidiana var. japonica Japanese Elm
Viburnum prunifolium Blackhaw Viburnum
Zelkova serrata Japanese Zelkova
Note: One tree that is noted for its resistance to wildfires is Sequoia sempervirens, Coast Redwood. This tree has bark that is up to one foot thick and contains no flammable resins. If damaged by fire, a redwood will readily sprout new branches or even an entirely new crown, and if the parent tree is killed, new buds will sprout from its base. Fires, moreover, appear to actually benefit redwoods by causing substantial mortality in competing species while having only minor effects on redwood. Burned areas are favorable to the successful germination of redwood seeds. Unfortunately, coast redwoods grow best in the foggy regions of coastal California and southern Oregon and not in fire prone areas.
Sources
- Abby, Buck, “Weather and Trees”, Landscape Online, November, 2012.
- Baughman, Mel, “Flooding Effects on Trees”, University of Minnesota Extension, 2012.
- Burban, Lisa and Andresen, John, “Storms Over the Urban Forest: Planning, Responding, and Regreening” USDA Forest Service, 1994.
- Craig, Charles C., “Storm Surges”, Volusia County Florida, 2012.
- Denver Water Co. "Planting Trees and Shrubs in Times of Drought and Water Restrictions", 2009.
- Duryea, Mary Eliana Kampf, “Wind and Trees: Lesson Learned from Hurricanes”, University of Florida, Publication No FOR 118, February 2011.
- Evans, Erv, “Drought Tolerant Trees”, North Carolina State University, 2000.
- Fire wise Communities, “Fire wise Landscaping and Plant Lists”, 2013.
- Hauer, Richard J., Jeffrey O. Dawson, and Les P. Werner, "Trees and Ice Storms: The Development of Ice Storm-Resistant Urban Tree Populations", Joint Publication 06-1, University of Wisconsin, and the University of Illinois, 2006.
- Iles, Jeff and Mark Gleason, “Understanding the Effects of Flooding on Trees”, Iowa State University Extension, 2008.
- Lain, Ken, “Landscapes that Resist Threats from Wildfires”, Watters Garden Center Blog, June 2013.
- Loeb, Robert E. and Samuel King, “Landslides and the Urban Forest”, Arboriculture & Urban Forestry, 37(5): September 2011.
- Mann, Gordon, “Trees during a Drought”, Archive #39 from Online Seminars for Municipal Arborists, July/August 2011.
- McIvor, Anna, et. al. “Storm Surge Reduction by Mangroves”, Natural Coastal Protection Series, Published by The Nature Conservancy and Wetlands International, 2012.
- Relf, Diane, and Bonnie Appleton, “Managing Winter Injury to Trees and Shrubs”, Virginia Cooperative Extension, Virginia Tech, and Virginia State University, May 1, 2009.
- Sacramento Tree Foundation, "Trees Are Great Especially During A Drought", 2008
- The UC Forest Products Laboratory, “Vegetation Guide for Landscaping in High Fire Risk Areas”, 1997.
- Urban Forest Manager, Approved Trees for the City of Chico, City of Chico General Services Department, December 2011.
The test that follows contains 80 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award 4.0 CEUs* for a passing grade. SAF members will earn 1.0 Cat. 1-CT credit for a passing grade. The cost for taking this test is $20 per credit. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 4.0 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, or BCMA science credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA and MTOA members may submit your ISA certification record to these organizations and receive credits one for one.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant / gibneyCE.com’. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website. *SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.