#8 Read About Follow-up Care
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.
Click on the green text in each section for more information
Tree Care After Installation
There is a common saying in the world of horticulture that during the first year after installation, a plant sleeps, the second year it creeps, and the third year it leaps. In actuality, the installation shock period for trees is approximately one year for each inch of stem caliper. Therefore, a three-inch caliper B&B tree will need at least three years in the landscape to recover from the shock of root loss. However, if the installation site is a particularly harsh site, which is typical for many urban installation sites, this shock period may continue much longer before the tree can creep and then leap. Trees installed from containers or bare root will recover faster because all their roots are transplanted. The moisture level is the controlling factor with containerized trees, as you will read later. Bare root trees experience the least amount of transplant shock because they have most of their roots and there is no adjustment required to adapt to a different soil. Topic #7 covered all you need to know about bare root trees. It is the tiny hairs attached to roots that absorb water. The more tiny root hairs that are protected from drying out on the roots during installation, the faster the tree recovers from transplant shock.
Watering
The transplant shock period should be considered as the period of intensive care. Maintenance practices should focus on eliminating or reducing all unnecessary stresses such as water stress (too much, too little), competition for root space from other plants (especially turfgrass), insect pests or pathogens that wound or defoliate the tree, nutrient deficiencies and unnecessary wounding. During this period, the tree’s energy should be focused on root growth and establishing a more characteristic root/shoot balance for that particular species. Rapid root growth is important to minimizing water stress after installation. Installed trees rely almost entirely on root ball moisture for most of the first growing season. Root balls dry out more rapidly than the surrounding backfill. According to recent research, 4 weeks after installation, a 1-gallon shrub requires ½ quart (½ liter) of water per day. After 11 weeks or 2 1/2 months, 1 quart (1 liter) is used per day and at 21 weeks or 5 months after installation 2 quarts (2 liters) of water are used per day. By the 21st week however, the roots have grown to the point there are 28 quarts (23 liters) of water available in the enlarged root zone so irrigation is no longer necessary.
Duration of Installation Stress
The time it takes to become fully established depends on several factors. Small trees recover faster than large trees because of the time it takes for the roots to regrow the distance they were before being dug. Certain species are known for this ease of transplanting. Oaks for example are difficult to transplant and will require more time to become established and they require more attention than other species. The climate is also a factor, so the warmer the soil for the longer period of time, the less time it takes a tree to recover. For example, in Florida, trees can recover in approximately 3 months per caliper inch, compared to 12 months in the colder climates.
Most trees experience shock after installation because of the disturbance to the root system. For example, in the upper Midwest, where soils are frozen in winter, tree roots grow an average of 18 inches (0.5m) a year. In Florida's sandy soils and year round growing season, trees will average 6 feet (2m) a year.
In the drier parts of central and western US, irrigation may have to supplement rainfall to provide enough water for survival before establishment. This is especially important if the trees are not adapted to the dry climates. Maximum daily root growth increments range from just a few inches (millimeters) in some species to over 2 in (56 mm) in black locust {Robinia pseudoacacia) though average daily growth is usually much less. Trees provided with regular irrigation through the first growing season after installation require approximately 3 months, 6 months (hardiness zones 7-8), or one year or more (hardiness zones 2-6) per inch (2.5 cm) of trunk diameter to fully establish roots in the landscape soil. Trees that are under-irrigated during this establishment period are likely to require additional time to establish because roots grow more slowly. Most trees are in fact, under-irrigated during the establishment period.
In balled and burlapped (B&B) installations, it is estimated that between 5% and 82% of the original root system is contained within the root ball depending on how the root system is measured and if any actions were taken to alter root growth in the nursery. Trees grow in balance between the above-ground portion of the tree and the root system to support it. When the amount of the root system is reduced during installation, the above-ground portion of the tree is also affected. The tree is either stimulated to regenerate more roots to balance the top, or the top partially dies back, or both until the shoots and roots establish equilibrium.
Regular irrigation after installation protects the tiny root hairs and encourages rapid root growth that is essential for tree establishment. Irrigation also helps maintain and encourage the desirable dominant leader in the tree canopy on large-maturing trees. Instead of a dominant leader, trees that are under-irrigated during the establishment period often develop undesirable, low, co-dominant stems and double leaders that can split from the tree later. Splits along the lower trunk have also been associated with under-irrigation after irrigation as shut off. Since most root growth occurs in the summer months, irrigation during this time is crucial. You could loose almost an entire year's root growth if you under-irrigate the first summer.
Root Regeneration
Root regeneration occurs soon after installation and this term refers to the replacement of roots that were lost during the digging process and are being replaced at the tips of the cut roots. These new roots grow in the same direction as the original root.
The rate of regeneration varies depending primarily on soil moisture, but also on soil type and species. The root ball must be kept sufficiently moist from the time the tree is dug until the roots have grown beyond the planting pit at the new site. Drought stress can occur even if the surrounding soil is moist, because the roots have not grown into the surrounding soil.
New root initiation can vary by species. Easy to install species such as green ash will initiate new roots after 17 – 29 days. Red oak is a difficult to transplant species and will take 24 – 49 days to generate new roots. The soil temperature can also cause a variation. Cool soils take a longer time to develop good root systems than warm soils. This is why a "blanket" of mulch is desired for keeping the soil warm, moist, and uniform in temperature.
When a tree is established, many roots will have grown a distance equal to approximately 3 times the distance from the trunk to the branch tips. During the establishment period, shoots and trunk grow slower than they did before transplanting. When their growth rates become more or less consistent from one year to the next, the tree is considered established.
When roots of bare root and containerized plants are not spread out properly at installation, permanently kinked and twisted roots can result. Also, proper root development and anchorage will not occur, and vascular flow may also be restricted. Girdling roots of field-grown stock, which is different than circling roots on container stock, can be formed as a result of transplanting. When installation cuts primary roots, the existing branch roots often begin to grow more rapidly. Under normal circumstances, these branch roots would have remained small and probably live only a few years, before being replaced by other roots. But after the primary root is cut, they do sometimes become a part of the permanent structural root system. Their perpendicular orientation to the other major roots and proximity to the base of the trunk, results in development of girdling roots as both the roots and the trunk continue to increase in diameter. These girdling roots restrict the flow in the vascular system and can cause stress, and eventually death to the tree. Additional evidence that girdling roots may result from transplanting is provided by the low incidence of girdling roots in nature.
Follow Up Care
After installing, be sure to indicate on city maps or lists, the trees being installed and the date at the given locations. Then remove tags and labels from the trees and shrubs to prevent girdling the branches and/or trunks. Good follow up watering helps promote root growth. Mulch, but don't over mulch newly installed trees and shrubs. Mulching with no more than 4 inches of mulch will help keep the moisture in the ground. Mulch also protects the root zone from a severe freeze or severe heat, and it encourages mycorrhizal formation on the roots. Mulch should be kept at least 6 inches away from the trunk.
If a tree should die, care should be taken to determine its cause before another tree is installed. If poor drainage is a problem, it should be corrected. If vandalism is a problem, have neighborhood kids help install larger trees in these areas. The kids will develop a sense of "ownership" which will help protect the tree from future vandalism attacks. Also add a large stake, 5 feet tall beside a tree to help protect it for its' first year. Install smaller trees in the parks and residential areas where vandalism is less likely to be a problem. If vandalism still occurs, consider the reasons for vandalism and make the necessary corrections before replanting. Typical reasons for vandalism include, planting at the wrong site, planting without "the neighborhood" permission or input, planting the wrong size or species, planting in a rival gang's "turf", etc. In areas of high pedestrian traffic, it may be necessary to install pavers, stone or brick, set in sand over the tree ball. This will have a negative impact on the tree's growth, but allow it to continue growing albeit slower.
Trees In Planters
In areas where all else fails, a large, above ground tree in a planter or container can be set on pavement. The container should be obtained commercially to insure a high strength, engineered container. In colder climates, it is also best that the container be insulated on the sides and have an irrigation system or water reservoir built in. The best containers have fill pipes, overflow drains, and reservoir drains. Containerized trees will require weekly watering, weeding, and constant attention. The best solution at locations where a decorative, landscaped container is required, is to install a large shrub such as a yew (Taxus) or upright Juniper (Juniperus) surrounded with groundcovers and perennials. A small-sized crabapple (Malus) that grows to 10 ft (3 m) is also a good choice.
Winter Care
Harsh climate is often responsible for severe damage to landscape plants. Winter sun, wind, and cold temperatures can bleach and desiccate evergreen foliage, damage bark, and injure or kill branches, flower buds, and roots. Snow and ice can break branches and topple entire trees. Salt used for deicing streets, sidewalks, and parking lots is harmful to landscape plantings. Winter food shortages force rodents and deer to feed on bark, twigs, flower buds, and foliage, injuring and sometimes killing trees and shrubs. All is not bleak however, as landscape plants can be protected to minimize injury.
Winter Pruning
Many arborists suggest that late autumn is the best time to determine a tree's pruning needs, when it is bare and its exposed branch structure allows detection and correction of problems previously hidden by foliage. Arborists also need to note any conflicts with utility wires or structures and check for weak branch unions and decay. If possible, save the removals for the winter when the ground is frozen. Winter removals do less damage to existing landscapes and are more cost effective for the client. There are no leaves to deal with and there is often better access for equipment and crew.
Tree Health Inspections
Various visible physical features can be observed to indicate the survival and general well-being of a newly installed tree. These include the examination of the foliage, twigs, bark and roots. The color of the foliage is an excellent diagnostic tool. A uniform bright green color over the entire crown with leaves fully formed is a reliable indicator of good health on hardwood species. Yellowing indicates water stress from too little or too much soil moisture or may indicate various degrees of nutrient deficiencies. Yellowing and immature leaves early in the spring usually indicates stress due to soil water logging during the dormant season. This condition commonly occurs on trees installed in compacted soils. Diagnosis for moisture stress of conifer foliage is somewhat more difficult. Examination of the soil conditions and roots may eliminate moisture stress as a cause.
Length of twig elongation as compared to previous growth is another indicator of plant health. An abrupt shortening of elongation as compared to previous growth indicates a problem. Some twig shortening should be expected due to transplant shock. Installing the roots too deep can be fatal, cause rotting and eventual failure, or unwanted sprouting of many species.
Though root examination is difficult, it is recommended when serious growth symptoms appear. The color of healthy, vigorous tree root tips is white to light yellow, with smooth surfaces. Root tips affected by poor aeration as in waterlogged soils are dark brown, purple or even black and have rough-looking surfaces. Deciduous tree roots may also be examined for stored carbohydrates. Also check the soil ball to be sure the tree has the right amount of water. Too much or too little water is the biggest problem a newly installed tree will have for its first 2 years. On well-drained sites, 10 gallons of water 2 times a week will provide a sufficient amount of root ball moisture for the first summer.
Sunscald, characterized by sunken, dried, or cracked bark, is caused by the heating effect of the winter sun in cold weather. It usually occurs on the south or southwest side of newly installed trees. In the autumn, to prevent sunscald as well as borers, cankers, and mechanical damage, wrap young and thin-barked trees with commercial tree wrap from the bottom up to the first major branch. Remove the wrap in spring. Thin-barked species such as maples and honey locusts may require protection for several years after installation.
Tree Care After Installation
There is a common saying in the world of horticulture that during the first year after installation, a plant sleeps, the second year it creeps, and the third year it leaps. In actuality, the installation shock period for trees is approximately one year for each inch of stem caliper. Therefore, a three-inch caliper B&B tree will need at least three years in the landscape to recover from the shock of root loss. However, if the installation site is a particularly harsh site, which is typical for many urban installation sites, this shock period may continue much longer before the tree can creep and then leap. Trees installed from containers or bare root will recover faster because all their roots are transplanted. The moisture level is the controlling factor with containerized trees, as you will read later. Bare root trees experience the least amount of transplant shock because they have most of their roots and there is no adjustment required to adapt to a different soil. Topic #7 covered all you need to know about bare root trees. It is the tiny hairs attached to roots that absorb water. The more tiny root hairs that are protected from drying out on the roots during installation, the faster the tree recovers from transplant shock.
Watering
The transplant shock period should be considered as the period of intensive care. Maintenance practices should focus on eliminating or reducing all unnecessary stresses such as water stress (too much, too little), competition for root space from other plants (especially turfgrass), insect pests or pathogens that wound or defoliate the tree, nutrient deficiencies and unnecessary wounding. During this period, the tree’s energy should be focused on root growth and establishing a more characteristic root/shoot balance for that particular species. Rapid root growth is important to minimizing water stress after installation. Installed trees rely almost entirely on root ball moisture for most of the first growing season. Root balls dry out more rapidly than the surrounding backfill. According to recent research, 4 weeks after installation, a 1-gallon shrub requires ½ quart (½ liter) of water per day. After 11 weeks or 2 1/2 months, 1 quart (1 liter) is used per day and at 21 weeks or 5 months after installation 2 quarts (2 liters) of water are used per day. By the 21st week however, the roots have grown to the point there are 28 quarts (23 liters) of water available in the enlarged root zone so irrigation is no longer necessary.
Duration of Installation Stress
The time it takes to become fully established depends on several factors. Small trees recover faster than large trees because of the time it takes for the roots to regrow the distance they were before being dug. Certain species are known for this ease of transplanting. Oaks for example are difficult to transplant and will require more time to become established and they require more attention than other species. The climate is also a factor, so the warmer the soil for the longer period of time, the less time it takes a tree to recover. For example, in Florida, trees can recover in approximately 3 months per caliper inch, compared to 12 months in the colder climates.
Most trees experience shock after installation because of the disturbance to the root system. For example, in the upper Midwest, where soils are frozen in winter, tree roots grow an average of 18 inches (0.5m) a year. In Florida's sandy soils and year round growing season, trees will average 6 feet (2m) a year.
In the drier parts of central and western US, irrigation may have to supplement rainfall to provide enough water for survival before establishment. This is especially important if the trees are not adapted to the dry climates. Maximum daily root growth increments range from just a few inches (millimeters) in some species to over 2 in (56 mm) in black locust {Robinia pseudoacacia) though average daily growth is usually much less. Trees provided with regular irrigation through the first growing season after installation require approximately 3 months, 6 months (hardiness zones 7-8), or one year or more (hardiness zones 2-6) per inch (2.5 cm) of trunk diameter to fully establish roots in the landscape soil. Trees that are under-irrigated during this establishment period are likely to require additional time to establish because roots grow more slowly. Most trees are in fact, under-irrigated during the establishment period.
In balled and burlapped (B&B) installations, it is estimated that between 5% and 82% of the original root system is contained within the root ball depending on how the root system is measured and if any actions were taken to alter root growth in the nursery. Trees grow in balance between the above-ground portion of the tree and the root system to support it. When the amount of the root system is reduced during installation, the above-ground portion of the tree is also affected. The tree is either stimulated to regenerate more roots to balance the top, or the top partially dies back, or both until the shoots and roots establish equilibrium.
Regular irrigation after installation protects the tiny root hairs and encourages rapid root growth that is essential for tree establishment. Irrigation also helps maintain and encourage the desirable dominant leader in the tree canopy on large-maturing trees. Instead of a dominant leader, trees that are under-irrigated during the establishment period often develop undesirable, low, co-dominant stems and double leaders that can split from the tree later. Splits along the lower trunk have also been associated with under-irrigation after irrigation as shut off. Since most root growth occurs in the summer months, irrigation during this time is crucial. You could loose almost an entire year's root growth if you under-irrigate the first summer.
Root Regeneration
Root regeneration occurs soon after installation and this term refers to the replacement of roots that were lost during the digging process and are being replaced at the tips of the cut roots. These new roots grow in the same direction as the original root.
The rate of regeneration varies depending primarily on soil moisture, but also on soil type and species. The root ball must be kept sufficiently moist from the time the tree is dug until the roots have grown beyond the planting pit at the new site. Drought stress can occur even if the surrounding soil is moist, because the roots have not grown into the surrounding soil.
New root initiation can vary by species. Easy to install species such as green ash will initiate new roots after 17 – 29 days. Red oak is a difficult to transplant species and will take 24 – 49 days to generate new roots. The soil temperature can also cause a variation. Cool soils take a longer time to develop good root systems than warm soils. This is why a "blanket" of mulch is desired for keeping the soil warm, moist, and uniform in temperature.
When a tree is established, many roots will have grown a distance equal to approximately 3 times the distance from the trunk to the branch tips. During the establishment period, shoots and trunk grow slower than they did before transplanting. When their growth rates become more or less consistent from one year to the next, the tree is considered established.
When roots of bare root and containerized plants are not spread out properly at installation, permanently kinked and twisted roots can result. Also, proper root development and anchorage will not occur, and vascular flow may also be restricted. Girdling roots of field-grown stock, which is different than circling roots on container stock, can be formed as a result of transplanting. When installation cuts primary roots, the existing branch roots often begin to grow more rapidly. Under normal circumstances, these branch roots would have remained small and probably live only a few years, before being replaced by other roots. But after the primary root is cut, they do sometimes become a part of the permanent structural root system. Their perpendicular orientation to the other major roots and proximity to the base of the trunk, results in development of girdling roots as both the roots and the trunk continue to increase in diameter. These girdling roots restrict the flow in the vascular system and can cause stress, and eventually death to the tree. Additional evidence that girdling roots may result from transplanting is provided by the low incidence of girdling roots in nature.
Follow Up Care
After installing, be sure to indicate on city maps or lists, the trees being installed and the date at the given locations. Then remove tags and labels from the trees and shrubs to prevent girdling the branches and/or trunks. Good follow up watering helps promote root growth. Mulch, but don't over mulch newly installed trees and shrubs. Mulching with no more than 4 inches of mulch will help keep the moisture in the ground. Mulch also protects the root zone from a severe freeze or severe heat, and it encourages mycorrhizal formation on the roots. Mulch should be kept at least 6 inches away from the trunk.
If a tree should die, care should be taken to determine its cause before another tree is installed. If poor drainage is a problem, it should be corrected. If vandalism is a problem, have neighborhood kids help install larger trees in these areas. The kids will develop a sense of "ownership" which will help protect the tree from future vandalism attacks. Also add a large stake, 5 feet tall beside a tree to help protect it for its' first year. Install smaller trees in the parks and residential areas where vandalism is less likely to be a problem. If vandalism still occurs, consider the reasons for vandalism and make the necessary corrections before replanting. Typical reasons for vandalism include, planting at the wrong site, planting without "the neighborhood" permission or input, planting the wrong size or species, planting in a rival gang's "turf", etc. In areas of high pedestrian traffic, it may be necessary to install pavers, stone or brick, set in sand over the tree ball. This will have a negative impact on the tree's growth, but allow it to continue growing albeit slower.
Trees In Planters
In areas where all else fails, a large, above ground tree in a planter or container can be set on pavement. The container should be obtained commercially to insure a high strength, engineered container. In colder climates, it is also best that the container be insulated on the sides and have an irrigation system or water reservoir built in. The best containers have fill pipes, overflow drains, and reservoir drains. Containerized trees will require weekly watering, weeding, and constant attention. The best solution at locations where a decorative, landscaped container is required, is to install a large shrub such as a yew (Taxus) or upright Juniper (Juniperus) surrounded with groundcovers and perennials. A small-sized crabapple (Malus) that grows to 10 ft (3 m) is also a good choice.
Winter Care
Harsh climate is often responsible for severe damage to landscape plants. Winter sun, wind, and cold temperatures can bleach and desiccate evergreen foliage, damage bark, and injure or kill branches, flower buds, and roots. Snow and ice can break branches and topple entire trees. Salt used for deicing streets, sidewalks, and parking lots is harmful to landscape plantings. Winter food shortages force rodents and deer to feed on bark, twigs, flower buds, and foliage, injuring and sometimes killing trees and shrubs. All is not bleak however, as landscape plants can be protected to minimize injury.
Winter Pruning
Many arborists suggest that late autumn is the best time to determine a tree's pruning needs, when it is bare and its exposed branch structure allows detection and correction of problems previously hidden by foliage. Arborists also need to note any conflicts with utility wires or structures and check for weak branch unions and decay. If possible, save the removals for the winter when the ground is frozen. Winter removals do less damage to existing landscapes and are more cost effective for the client. There are no leaves to deal with and there is often better access for equipment and crew.
Tree Health Inspections
Various visible physical features can be observed to indicate the survival and general well-being of a newly installed tree. These include the examination of the foliage, twigs, bark and roots. The color of the foliage is an excellent diagnostic tool. A uniform bright green color over the entire crown with leaves fully formed is a reliable indicator of good health on hardwood species. Yellowing indicates water stress from too little or too much soil moisture or may indicate various degrees of nutrient deficiencies. Yellowing and immature leaves early in the spring usually indicates stress due to soil water logging during the dormant season. This condition commonly occurs on trees installed in compacted soils. Diagnosis for moisture stress of conifer foliage is somewhat more difficult. Examination of the soil conditions and roots may eliminate moisture stress as a cause.
Length of twig elongation as compared to previous growth is another indicator of plant health. An abrupt shortening of elongation as compared to previous growth indicates a problem. Some twig shortening should be expected due to transplant shock. Installing the roots too deep can be fatal, cause rotting and eventual failure, or unwanted sprouting of many species.
Though root examination is difficult, it is recommended when serious growth symptoms appear. The color of healthy, vigorous tree root tips is white to light yellow, with smooth surfaces. Root tips affected by poor aeration as in waterlogged soils are dark brown, purple or even black and have rough-looking surfaces. Deciduous tree roots may also be examined for stored carbohydrates. Also check the soil ball to be sure the tree has the right amount of water. Too much or too little water is the biggest problem a newly installed tree will have for its first 2 years. On well-drained sites, 10 gallons of water 2 times a week will provide a sufficient amount of root ball moisture for the first summer.
Sunscald, characterized by sunken, dried, or cracked bark, is caused by the heating effect of the winter sun in cold weather. It usually occurs on the south or southwest side of newly installed trees. In the autumn, to prevent sunscald as well as borers, cankers, and mechanical damage, wrap young and thin-barked trees with commercial tree wrap from the bottom up to the first major branch. Remove the wrap in spring. Thin-barked species such as maples and honey locusts may require protection for several years after installation.
Stabilizing
Stabilizing trees by using the latest products is rapidly replacing staking and guying as the preferred method to encourage rapid root growth on newly installed trees.
A below-grade system secures new plantings by the root-ball. A long “staple” or stake is placed through the root ball to hold and stabilize the roots in contact with the bottom of the planting pit and to hold the root system in place. Below-grade stabilizing replaces the roots left in the nursery. When the roots are stabilized, there is improved root growth and the trunk is allowed to move in response to its surrounding conditions. Below-grade stabilizing reduces the chance that newly sprouting roots will be broken off during wind gusts. Staple manufacturers indicate that the staple can be removed after one season or if left in place, will eventually rust away. Another option is to build staples out of three pieces of wood screwed together.
Stabilizing benefits include:
The American Nursery and Landscape Association (ANLA) encourages all municipalities, landscape architects, and landscape installers to consider using root stabilization systems. Research has shown that trunk guying may be detrimental to a tree’s growth but when secured by the root-ball, trees flex through the length of the trunk. They develop a better overall taper and become more tolerant of wind and vandalism.
Problem with stabilizing
Unless the metal staple product is removed after a couple of years, it might be a problem when the tree dies or is removed. The stump grinding equipment can be severely damaged when it hits the metal staple if it has not rusted away or been recycled to another tree.
Stabilizing trees by using the latest products is rapidly replacing staking and guying as the preferred method to encourage rapid root growth on newly installed trees.
A below-grade system secures new plantings by the root-ball. A long “staple” or stake is placed through the root ball to hold and stabilize the roots in contact with the bottom of the planting pit and to hold the root system in place. Below-grade stabilizing replaces the roots left in the nursery. When the roots are stabilized, there is improved root growth and the trunk is allowed to move in response to its surrounding conditions. Below-grade stabilizing reduces the chance that newly sprouting roots will be broken off during wind gusts. Staple manufacturers indicate that the staple can be removed after one season or if left in place, will eventually rust away. Another option is to build staples out of three pieces of wood screwed together.
Stabilizing benefits include:
- There are no above ground obstructions and the desired look of a completed landscape is immediate.
- No maintenance or disposal is required because there is no need to remove the staples, unless the arborist or landscape architect wishes to recycle the staple for another tree.
- Some below-grade stabilizers can be completely installed with a sledge-hammer in one minute.
- There is nothing to constrict the trunk; therefore, girdling, bark damage, and potential breaking from stress due to guying materials are eliminated.
- Recent research has discovered that the tree actually develops an oval cross section to deal with prevailing winds. This is not a problem if the tree is stabilized, but it cannot occur if the tree is staked or guyed.
The American Nursery and Landscape Association (ANLA) encourages all municipalities, landscape architects, and landscape installers to consider using root stabilization systems. Research has shown that trunk guying may be detrimental to a tree’s growth but when secured by the root-ball, trees flex through the length of the trunk. They develop a better overall taper and become more tolerant of wind and vandalism.
Problem with stabilizing
Unless the metal staple product is removed after a couple of years, it might be a problem when the tree dies or is removed. The stump grinding equipment can be severely damaged when it hits the metal staple if it has not rusted away or been recycled to another tree.
Staking
There are times when a tree needs to be supported with a stake and flexible guy wire that will control the amount of tree sway in the wind. Staking may be needed for street trees to stabilize against jostling from pedestrian traffic. Young trees standing alone with their tops free to move will develop stronger, more resilient trunks than those staked for several years. The stem from long term staking may in fact become thicker above the tie than below it because diameter growth increases in response to the movement of the crown. If the tree can flex only above the height of the guy wire, it is easy to snap the crown off by using the tie as a pivot.
A supported tree will initially gain height faster than the unsupported tree, but the stem will be thin and weak up to the tie and then it will taper rapidly. Normally, when a tree bends as a result of wind, root development on the windward side of the tree is increased, thereby aiding the tree in becoming stronger and eventually straightening up on its own.
Every newly installed tree should be assessed independently on whether or not it should be staked or stabilized. The tree is not as likely to be girdled by these attachments in one growing season, but if they are left on for too long they will girdle a tree or weaken it.
Staking Systems
Staking systems can vary from inexpensive wood stakes with wire or cable to very expensive manufactured staking systems. Staking systems can also vary according to the size of the tree. The common characteristic of any staking system is that it requires time to install and maintain.
Staking should only be used:
Problems with staking:
Guying
Trunk stabilizing with guy wires has been the traditional method for stabilizing newly installed trees for centuries. It is believed that trunk stabilizing came with the trees that were lashed to the decks of early trade ships. A guying system secures new plantings with long wires running from the ground to the first third the distance up the trunk where the wire is secured around the trunk. This system is designed for trees exceeding twenty feet in height and all evergreens over 8 feet and will have guy wire systems with turnbuckles and earth anchors. Tree bracing collars made of flexible plastic or nylon tape, manufactured for this purpose, or twist braces that allow for flexibility of the tree trunk should be used instead of hose and wire. These braces are also recyclable. Too often, a guy wire is tight around the trunk and will effectively girdle and kill the tree.
Problems with guying:
Wrapping
Most trees do not need to be wrapped except in extremely harsh sites or to protect thin barked trees. If a tree comes from the nursery with a wrapped trunk, remove it after installation. If wraps are desired because of a thin-barked tree, they should be removed within one year. To avoid trunk girdling, do not attach wraps with wire, nylon rope, plastic ties, or electrical tape. If cared for and maintained properly and regularly, wrapping materials are worthwhile until the tree becomes established.
Pros of Wrapping
Cons of Wrapping
Unfortunately, there is still a lot of controversy surrounding the use of tree wrap for winter protection. No harm will come from placing light-colored wrapping on the bole in late autumn and removing it in early spring, but the cold-damage benefits are debatable. To prevent rodent damage, install a plastic or woven wire collar around the trunk instead of tree wrap. Trees that are water-stressed going into dormancy are more likely to suffer splits to the bark. Tree shelters or growing tubes are better than tape because they allow sunlight and air to flow around the bark.
Trunk injury from equipment causes serious damage to trees. Regular weed control in a large diameter circle around the trunk is the best way to protect the trunk of a recently installed tree. Stakes protect the tree from accidental injury.
There are times when a tree needs to be supported with a stake and flexible guy wire that will control the amount of tree sway in the wind. Staking may be needed for street trees to stabilize against jostling from pedestrian traffic. Young trees standing alone with their tops free to move will develop stronger, more resilient trunks than those staked for several years. The stem from long term staking may in fact become thicker above the tie than below it because diameter growth increases in response to the movement of the crown. If the tree can flex only above the height of the guy wire, it is easy to snap the crown off by using the tie as a pivot.
A supported tree will initially gain height faster than the unsupported tree, but the stem will be thin and weak up to the tie and then it will taper rapidly. Normally, when a tree bends as a result of wind, root development on the windward side of the tree is increased, thereby aiding the tree in becoming stronger and eventually straightening up on its own.
Every newly installed tree should be assessed independently on whether or not it should be staked or stabilized. The tree is not as likely to be girdled by these attachments in one growing season, but if they are left on for too long they will girdle a tree or weaken it.
Staking Systems
Staking systems can vary from inexpensive wood stakes with wire or cable to very expensive manufactured staking systems. Staking systems can also vary according to the size of the tree. The common characteristic of any staking system is that it requires time to install and maintain.
Staking should only be used:
- when the new trees have abnormally small root systems that can't physically support the larger above-ground growth.
- when the tree is of a substantial size.
- when the stem is spindly and bends excessively if it is not supported.
- when the tree is a palm, which usually have a small root ball.
- when the planting site is very windy and trees will be uprooted if they are not visually supported.
- when there is a good chance vandals will uproot or damage visually unprotected trees.
- when the soil is comprised of sand or other loose-textured material.
Problems with staking:
- Trees need to move without restriction from the ground up in order to develop the proper trunk taper.
- Staking causes some trees to break above the tie and can also restrict the flow of sugars.
- Often the staking system is not adjusted properly or it is left on the tree for too long.
- Trunk staking requires time to install, maintain, and remove.
Guying
Trunk stabilizing with guy wires has been the traditional method for stabilizing newly installed trees for centuries. It is believed that trunk stabilizing came with the trees that were lashed to the decks of early trade ships. A guying system secures new plantings with long wires running from the ground to the first third the distance up the trunk where the wire is secured around the trunk. This system is designed for trees exceeding twenty feet in height and all evergreens over 8 feet and will have guy wire systems with turnbuckles and earth anchors. Tree bracing collars made of flexible plastic or nylon tape, manufactured for this purpose, or twist braces that allow for flexibility of the tree trunk should be used instead of hose and wire. These braces are also recyclable. Too often, a guy wire is tight around the trunk and will effectively girdle and kill the tree.
Problems with guying:
- Trees need to move without restriction from the root collar.
- Guying places unnatural stress and the chance of breaking the tree at the point where the guying materials attach to the trunk.
- Often the guying material is not adjusted properly or it is left on the tree for too long.
- Girdling occurs where the tree begins to grow around the offending guying materials, absorbing them into the trunk.
- Trunk stabilizing requires time to install, maintain, and remove.
Wrapping
Most trees do not need to be wrapped except in extremely harsh sites or to protect thin barked trees. If a tree comes from the nursery with a wrapped trunk, remove it after installation. If wraps are desired because of a thin-barked tree, they should be removed within one year. To avoid trunk girdling, do not attach wraps with wire, nylon rope, plastic ties, or electrical tape. If cared for and maintained properly and regularly, wrapping materials are worthwhile until the tree becomes established.
Pros of Wrapping
- Many arborists and landscape architects think that sunscald may be prevented with white tree wraps on thin-barked trees (ex. maple, birch, cherry and beech) especially if trees are installed on southern exposures or paved areas that accumulate heat.
- A wrap is useful in preventing injury during digging and transplanting.
Cons of Wrapping
- Gas exchange on the trunk is limited.
- Moisture is retained between the wrap and the tree trunk.
- Wrapping provides a habitat for insects, disease, and trapped water damage to tree trunks.
- Beneath the bark is a layer of green cortex that contains chlorophyll that traps energy from the sun. This bark should not be covered.
- Sometimes wrap is used to hide wounds, purchaser beware!
Unfortunately, there is still a lot of controversy surrounding the use of tree wrap for winter protection. No harm will come from placing light-colored wrapping on the bole in late autumn and removing it in early spring, but the cold-damage benefits are debatable. To prevent rodent damage, install a plastic or woven wire collar around the trunk instead of tree wrap. Trees that are water-stressed going into dormancy are more likely to suffer splits to the bark. Tree shelters or growing tubes are better than tape because they allow sunlight and air to flow around the bark.
Trunk injury from equipment causes serious damage to trees. Regular weed control in a large diameter circle around the trunk is the best way to protect the trunk of a recently installed tree. Stakes protect the tree from accidental injury.
Watering Trees After Installation
The most neglected part of the installation process is an extended commitment to watering during the critical months following installation. Part of the problem lies in the fact that specific recommendations about frequency and amount of water to apply are almost impossible to give, especially for sites where soils have been altered. Water is essential for the tree to manufacture food. It also acts as a coolant, keeping the tree from overheating on summer days. Water serves as a system for transporting food throughout the tree. The lack of available water reduces the tree’s ability to make food and maintain normal functions. Symptoms of water stress include wilting and loss of leaves.
The removal of branches at installation for compensatory pruning was a common practice in the past. It was thought that fewer leaves meant less demand for water, leading to better establishment. However, this practice was found to be wrong. Research has found that trees establish more quickly without compensatory pruning, provided they are watered frequently. The more leaves they have to provide food for new growth, the faster the tree recovers from transplant shock.
Watering New Trees
When a tree is installed, the hole should be filled with water when the installation is halfway done and again when the tree is completely installed. Jiggle the tree back and forth a couple of times, with water in the hole, to ensure that the roots are in contact with the soil. The saucer should be filled two more times within 24 hours after installation. Even if it is raining, a thorough watering will eliminate trapped air pockets and reduce transplant shock. After installation, a thorough watering once a week is necessary until the end of the first growing season. On extremely hot or windy days, a very fine misting of the leaves may be necessary several times a day. Watering may also be necessary during drought periods for a few years after installation.
Frequently irrigated trees and shrubs take less time to establish than those receiving infrequent irrigation. This seems especially true for container-grown nursery stock. Initially, the best place to check water need is in the root ball or soils in direct contact with the roots. Moisture in these relatively small areas will be the primary source of water for the tree until the root system grows into the backfill.
Recent evidence suggests frequent irrigation provides more benefit than applying large volumes of water infrequently. This is in direct contrast to the out-of-date recommendation for established trees, where occasional irrigation with large water volumes is considered better than light, frequent applications. Be sure to gradually increase the area irrigated around the tree to accommodate root growth.
Historically, tree-watering guidelines have suggested watering trees every seven to ten days with 1 to 1½ gallons per-stem-caliper inch. While this frequency and amount of water may work in some situations, recent research suggests more frequent watering is necessary for optimal root establishment. Within two to three days, root balls of newly installed trees will dry to levels that impede root growth.
The maximum size tree to purchase should be determined not only by the budget, but also by irrigation capabilities and climate. If irrigation cannot be provided, choose smaller nursery stock to ensure survival. If trees will be irrigated infrequently, only seeds, seedlings, or small saplings of drought tolerant trees should be installed. Small-sized nursery stock has a small top, so roots come into balance with the tree soon after installation. Once roots come into balance with the top of the tree, they usually grow well with rainfall alone. If trees will be irrigated only until they are established, drought tolerant trees should be chosen, and nursery stock of any size can be installed.
Roots must generate and grow into surrounding soils before a larger soil volume can be tapped for moisture. Tree roots grow approximately 18 inches in length annually in most locations. Trees will become established within 1 – 1½ years for each caliper inch of stem. Thus, it takes 3 – 4 years before a 3” tree is established; 1” – 2” trees have less root loss and recover faster than 2” – 3” trees. The major reason to not purchase a smaller tree is when vandalism is a potential problem but then tree size probably won't matter.
This is another reason why arborists and landscape architects should consider planting smaller trees whenever possible. Not only are they less expensive to purchase and plant, but they also require less maintenance to become established. Five years after installation there is no visual difference in size and appearance of two trees, one purchased an inch in diameter and another purchased with a 2 inch (5 cm) diameter. In addition, for the budget, you can purchase 2 – 1” (2.5 cm) trees for the same price as 1 – 2” tree.
Mulching trees to a 2 – 3 inch (5 – 8 cm) depth is recommended as it helps reduce evaporation and conserve water.
Water can be applied with the use of commercially manufactured water tubes. TreeDiaper®, Treegator®, Snake®, Growth Ring®, and others, designed to hold water and release it slowly, can maintain relatively uniform soil moisture conditions and are especially useful if the soil absorbs water very slowly. Frequency of watering should be reduced and the area to be watered enlarged as the root system grows and expands. Newly installed trees and shrubs should not be irrigated as frequently or with the same amount of water as newly installed turf grass. Shady spots may not require as much water as sunny areas. Automatic irrigation systems must be monitored continuously and turned off during periods of heavy rainfall. Apply water in the early morning or late evening to avoid quick evaporation that would occur during warmer daylight hours.
Different species of trees and different soils make a general, overall watering recommendation unrealistic. The arborist or landscape architect overseeing the tree installation program must adapt the watering recommendations to accommodate different species and different soils.
Autumn Watering
To prevent or reduce the incidence of winter injury (winter browning on conifers in particular), arborists have adopted the practice of thoroughly soaking their newly installed woody plants just prior to soil freeze-up. This implies that the critical time for watering is just prior to freeze-up and that trees need to replace moisture lost via transpiration.
But there are two problems with this long-standing recommendation:
1) In climates with severe winters, it is unlikely that trees would have the opportunity to replace lost moisture since the soil is frozen from early December to sometime in March.
2) Cold hardiness research has shown slight moisture stress accelerates cold acclimation, and lower tissue water levels frequently correspond to greater low temperature tolerance. Researchers have demonstrated plant root tissues actually become more resistant to water uptake and/or translocation during the onset of cold acclimation.
The most neglected part of the installation process is an extended commitment to watering during the critical months following installation. Part of the problem lies in the fact that specific recommendations about frequency and amount of water to apply are almost impossible to give, especially for sites where soils have been altered. Water is essential for the tree to manufacture food. It also acts as a coolant, keeping the tree from overheating on summer days. Water serves as a system for transporting food throughout the tree. The lack of available water reduces the tree’s ability to make food and maintain normal functions. Symptoms of water stress include wilting and loss of leaves.
The removal of branches at installation for compensatory pruning was a common practice in the past. It was thought that fewer leaves meant less demand for water, leading to better establishment. However, this practice was found to be wrong. Research has found that trees establish more quickly without compensatory pruning, provided they are watered frequently. The more leaves they have to provide food for new growth, the faster the tree recovers from transplant shock.
Watering New Trees
When a tree is installed, the hole should be filled with water when the installation is halfway done and again when the tree is completely installed. Jiggle the tree back and forth a couple of times, with water in the hole, to ensure that the roots are in contact with the soil. The saucer should be filled two more times within 24 hours after installation. Even if it is raining, a thorough watering will eliminate trapped air pockets and reduce transplant shock. After installation, a thorough watering once a week is necessary until the end of the first growing season. On extremely hot or windy days, a very fine misting of the leaves may be necessary several times a day. Watering may also be necessary during drought periods for a few years after installation.
Frequently irrigated trees and shrubs take less time to establish than those receiving infrequent irrigation. This seems especially true for container-grown nursery stock. Initially, the best place to check water need is in the root ball or soils in direct contact with the roots. Moisture in these relatively small areas will be the primary source of water for the tree until the root system grows into the backfill.
Recent evidence suggests frequent irrigation provides more benefit than applying large volumes of water infrequently. This is in direct contrast to the out-of-date recommendation for established trees, where occasional irrigation with large water volumes is considered better than light, frequent applications. Be sure to gradually increase the area irrigated around the tree to accommodate root growth.
Historically, tree-watering guidelines have suggested watering trees every seven to ten days with 1 to 1½ gallons per-stem-caliper inch. While this frequency and amount of water may work in some situations, recent research suggests more frequent watering is necessary for optimal root establishment. Within two to three days, root balls of newly installed trees will dry to levels that impede root growth.
The maximum size tree to purchase should be determined not only by the budget, but also by irrigation capabilities and climate. If irrigation cannot be provided, choose smaller nursery stock to ensure survival. If trees will be irrigated infrequently, only seeds, seedlings, or small saplings of drought tolerant trees should be installed. Small-sized nursery stock has a small top, so roots come into balance with the tree soon after installation. Once roots come into balance with the top of the tree, they usually grow well with rainfall alone. If trees will be irrigated only until they are established, drought tolerant trees should be chosen, and nursery stock of any size can be installed.
Roots must generate and grow into surrounding soils before a larger soil volume can be tapped for moisture. Tree roots grow approximately 18 inches in length annually in most locations. Trees will become established within 1 – 1½ years for each caliper inch of stem. Thus, it takes 3 – 4 years before a 3” tree is established; 1” – 2” trees have less root loss and recover faster than 2” – 3” trees. The major reason to not purchase a smaller tree is when vandalism is a potential problem but then tree size probably won't matter.
This is another reason why arborists and landscape architects should consider planting smaller trees whenever possible. Not only are they less expensive to purchase and plant, but they also require less maintenance to become established. Five years after installation there is no visual difference in size and appearance of two trees, one purchased an inch in diameter and another purchased with a 2 inch (5 cm) diameter. In addition, for the budget, you can purchase 2 – 1” (2.5 cm) trees for the same price as 1 – 2” tree.
Mulching trees to a 2 – 3 inch (5 – 8 cm) depth is recommended as it helps reduce evaporation and conserve water.
Water can be applied with the use of commercially manufactured water tubes. TreeDiaper®, Treegator®, Snake®, Growth Ring®, and others, designed to hold water and release it slowly, can maintain relatively uniform soil moisture conditions and are especially useful if the soil absorbs water very slowly. Frequency of watering should be reduced and the area to be watered enlarged as the root system grows and expands. Newly installed trees and shrubs should not be irrigated as frequently or with the same amount of water as newly installed turf grass. Shady spots may not require as much water as sunny areas. Automatic irrigation systems must be monitored continuously and turned off during periods of heavy rainfall. Apply water in the early morning or late evening to avoid quick evaporation that would occur during warmer daylight hours.
Different species of trees and different soils make a general, overall watering recommendation unrealistic. The arborist or landscape architect overseeing the tree installation program must adapt the watering recommendations to accommodate different species and different soils.
Autumn Watering
To prevent or reduce the incidence of winter injury (winter browning on conifers in particular), arborists have adopted the practice of thoroughly soaking their newly installed woody plants just prior to soil freeze-up. This implies that the critical time for watering is just prior to freeze-up and that trees need to replace moisture lost via transpiration.
But there are two problems with this long-standing recommendation:
1) In climates with severe winters, it is unlikely that trees would have the opportunity to replace lost moisture since the soil is frozen from early December to sometime in March.
2) Cold hardiness research has shown slight moisture stress accelerates cold acclimation, and lower tissue water levels frequently correspond to greater low temperature tolerance. Researchers have demonstrated plant root tissues actually become more resistant to water uptake and/or translocation during the onset of cold acclimation.
Mulching Trees
The use of organic mulches in landscape situations mimics the natural processes that occur in deciduous forests where a "blanket" of leaves is deposited on the forest floor every autumn. Leaves act to insulate the soil in winter and are the mechanism by which carbon and mineral nutrients are recycled through the ecosystem. In the urban situation, adding mulch is a very important part of tree care that mimics the leaves in the forest.
Mulch Types
Mulch is anything that will facilitate the improvement of the microorganisms in the soil and can be any locally available product that will simulate the natural processes. Organic mulches include: composted yard waste, shredded or chunk pine bark, pine needles or pine straw, wood chips, lumber yard wood waste, nut shells, ground corn cobs, cocoa shells, buckwheat hulls, cow and horse manure, and garden composts. Inorganic mulches include volcanic or lava rock, crushed coral, pea gravel, crushed brick, and river rocks. Organic mulches break down over time and become part of the soil while inorganic mulch does not. Though there is no best mulch, except leaves on the forest floor, organic mulches are better for the tree. Mulch from coniferous plants is best for conifers; hardwood mulch is best for around hardwood trees.
Mulch Depth
Coarse-textured mulches should be placed 2 – 4 inches (5 – 10 cm) deep to provide oxygen diffusion into the soil. Finer-textured mulch may need only a 1 – 2 inches (2½ – 5 cm) layer. On poorly drained or wet soils, mulch depths should not exceed 2 inches (5 cm), especially for shallow rooted plants. Trees installed on wet sites might also appreciate being somewhat elevated if there is no oxygen in the super saturated soils. In this case, the mulch should be just a single layer thick.
Renewing mulch layers periodically should be done with as much care as the first layer. A light raking of existing mulch may be all that is needed to break through the layers. However, an annual addition of 1 – 2 inches (2½ – 5 cm) of new mulch is usually best. Newly installed trees should have mulch in the plant saucers 3 – 4 inches (8 – 10 cm) deep to form a 3 – 6 foot (1 – 2 m) diameter circle around the plant. As a tree becomes larger, annually expand the mulch to a 10 – 12 foot (3 – 4 m) diameter ring.
Benefits of Organic Mulch
Since inorganic mulches, such as rubber or lava rock, add nothing to the soil they may be less desirable than organic mulches. Inorganic mulches have applications in locations where organic mulches might blow away or be damaged by traffic on the mulch.
Problems with Mulch
Nutrient Levels of Mulch
Decomposing bacteria and fungi must have an ample supply of nitrogen to provide benefits to the tree. The bacteria in the soil utilize the existing nitrogen to break down the mulch, causing temporary nitrogen deficiencies on new growth.
Acid Levels
“Sour” mulch can occur when mulch is piled such that inadequate air exchange occurs. Without adequate oxygen, anaerobic microorganisms become active and cause the mulch to give off odors and to produce extremely acidic pH levels. Such mulch is highly toxic to plants. Avoid using it until it is properly composted. The continuous use of the same type of mulch may also contribute to plant stress by changing the soil’s acidity level. Acidic mulches like pine bark may have a pH of 3.5 – 4.5 when applied frequently. Due to the increased solubility of many micro-nutrients in acidic soil, toxic levels may lead to plant stress, which allows pathogens and insects to invade. Conversely, hardwood bark mulch may cause the soil to become too basic. Periodically monitoring soil pH and rotating the type of mulch used can reduce changes in soil acidity.
Allelopathic toxins
Allelopathic toxins are compounds produced by plants that inhibit the growth of other plants. The classic example of allelopathy is found in the black walnut (Juglans nigra). It produces juglone and juglonic acid, which inhibit the growth of many plants. Fresh wood chips from black walnut should not be used as mulch unless well composted. Other allelopathic mulches include uncomposted sawdust of redwood (Sequoia) and cedar (Cedrus) and the bark of spruce (Picea), larch (Larix), and Douglas fir (Pseudotsuga).
Excessive Mulch
Excessive use of piled mulch such as "volcanoes", which are inverted cones of mulch creeping up the trunks of trees, can induce fermentation, immobilize nutrients, increase the amount of moisture next to the trunk, cut off the oxygen supply, and kill trees. The application of an excessive layer of mulch is common where mulch is used decoratively around a tree. Tree roots, in an effort to find more oxygen, will commonly grow above the soil surface into the mulch. This makes those roots more susceptible to drought, temperature extremes, frost heaving, and bark abrasion especially if using inorganic mulches. Trees that have been wounded on the stem are predisposed to stem canker pathogens if the mulch is covering the wound. Trees are prone to form adventitious roots that develop into stem girdling roots. These effects of over-mulching are not immediately observed. It may take a few years for the affects to be noticed.
Keep mulch from touching tree trunks and shrub stems. A rule of thumb is 3 to 5 inches (8 – 12 cm) away from young plants, and 8 to 12 inches (20 – 30 cm) away from mature tree trunks.
Root Suffocation
Suffocation of roots is the most common cause of death from over-mulching. Excessive mulch can contribute to a waterlogged root zone. With water occupying most soil pore space, air content is minimal and diffusion of oxygen is blocked. When soil oxygen levels drop below 10%, root growth declines. Oxygen starvation is especially common in the spring, autumn, during wet periods, and in soils that do not have good drainage.
Bark Death
Inner bark death comes from these volcanoes because the trunk tissue is quite different from root tissue and cannot survive in a continually moist environment. This also occurs when trees are installed too deep and the flare is buried. Most diseases require moisture to reproduce and spread. Trunk diseases gain a foothold in the moist, decaying bark tissue under the mulch. The disease organisms ultimately invade the inner bark, disrupting food transport and finally killing the plant. This is compounded by the presence of bark beetles and borers.
Wet mulch layers piled up next to the trunk may begin to heat up when the mulch begins to decompose (similar to composting), where temperatures may reach 120° – 140° F (50° – 60°C). This high heat level may kill the inner bark of young trees and prevent the hardening-off period, causing the tissue to die.
Rodents
Piles of mulch next to the trunk may also provide cover for chewing rodents. These rodents live in the warm mulch and chew on the nutritious inner bark. This often goes unnoticed until spring when the tree is dead. If the trunk is chewed over 50%, there is little that can be done to save it except for bridge grafting.
Solution
If mulch volcanoes are observed in the landscape, pull them down and away from the stems and spread them out over a larger area.
The use of organic mulches in landscape situations mimics the natural processes that occur in deciduous forests where a "blanket" of leaves is deposited on the forest floor every autumn. Leaves act to insulate the soil in winter and are the mechanism by which carbon and mineral nutrients are recycled through the ecosystem. In the urban situation, adding mulch is a very important part of tree care that mimics the leaves in the forest.
Mulch Types
Mulch is anything that will facilitate the improvement of the microorganisms in the soil and can be any locally available product that will simulate the natural processes. Organic mulches include: composted yard waste, shredded or chunk pine bark, pine needles or pine straw, wood chips, lumber yard wood waste, nut shells, ground corn cobs, cocoa shells, buckwheat hulls, cow and horse manure, and garden composts. Inorganic mulches include volcanic or lava rock, crushed coral, pea gravel, crushed brick, and river rocks. Organic mulches break down over time and become part of the soil while inorganic mulch does not. Though there is no best mulch, except leaves on the forest floor, organic mulches are better for the tree. Mulch from coniferous plants is best for conifers; hardwood mulch is best for around hardwood trees.
Mulch Depth
Coarse-textured mulches should be placed 2 – 4 inches (5 – 10 cm) deep to provide oxygen diffusion into the soil. Finer-textured mulch may need only a 1 – 2 inches (2½ – 5 cm) layer. On poorly drained or wet soils, mulch depths should not exceed 2 inches (5 cm), especially for shallow rooted plants. Trees installed on wet sites might also appreciate being somewhat elevated if there is no oxygen in the super saturated soils. In this case, the mulch should be just a single layer thick.
Renewing mulch layers periodically should be done with as much care as the first layer. A light raking of existing mulch may be all that is needed to break through the layers. However, an annual addition of 1 – 2 inches (2½ – 5 cm) of new mulch is usually best. Newly installed trees should have mulch in the plant saucers 3 – 4 inches (8 – 10 cm) deep to form a 3 – 6 foot (1 – 2 m) diameter circle around the plant. As a tree becomes larger, annually expand the mulch to a 10 – 12 foot (3 – 4 m) diameter ring.
Benefits of Organic Mulch
- Conserves soil moisture
- Minimizes weed competition with tree roots
- Moderates extremes in surface soil temperatures
- Reduces soil erosion
- In dry situations, restricts soil cracking
- Reduces soil crusting
- Reduces soil compaction
- Improves soil aeration and soil structure
- May increase soil fertility
- Can reduce salt buildup
- Protects tree trunk from mowers, weed whips, etc.
- Mulched trees grow faster and healthier than non-mulched trees.
- Reduces maintenance costs
- Green mulch also brings many of these benefits, although it will compete with the tree for water and nutrients.
Since inorganic mulches, such as rubber or lava rock, add nothing to the soil they may be less desirable than organic mulches. Inorganic mulches have applications in locations where organic mulches might blow away or be damaged by traffic on the mulch.
Problems with Mulch
- Fresh organic mulches (green mulch) temporarily deplete soil nitrogen in the top inch of soil, which is not really a problem because the nitrogen is replaced when the mulch has finished decomposing and is cured.
- Geotextile fabrics used as mulch can lead to higher soil temperatures and rainwater barriers.
- Black plastic and peat moss can cause many problems such as root surfacing and creating a moisture barrier.
- Supplemental nitrogen is sometimes needed to speed up the decomposition process.
- Mulch can provide habitat for rodents, as well as for slugs and snails.
- Improperly applied mulches can prevent water from moving into the soil.
- Certain fungi grow in dry mulches and prevent water from penetrating the soil.
- Mulch that is too thick or piled against the trunk increases stress, which can lead to disease,
and insect problems.
Nutrient Levels of Mulch
Decomposing bacteria and fungi must have an ample supply of nitrogen to provide benefits to the tree. The bacteria in the soil utilize the existing nitrogen to break down the mulch, causing temporary nitrogen deficiencies on new growth.
Acid Levels
“Sour” mulch can occur when mulch is piled such that inadequate air exchange occurs. Without adequate oxygen, anaerobic microorganisms become active and cause the mulch to give off odors and to produce extremely acidic pH levels. Such mulch is highly toxic to plants. Avoid using it until it is properly composted. The continuous use of the same type of mulch may also contribute to plant stress by changing the soil’s acidity level. Acidic mulches like pine bark may have a pH of 3.5 – 4.5 when applied frequently. Due to the increased solubility of many micro-nutrients in acidic soil, toxic levels may lead to plant stress, which allows pathogens and insects to invade. Conversely, hardwood bark mulch may cause the soil to become too basic. Periodically monitoring soil pH and rotating the type of mulch used can reduce changes in soil acidity.
Allelopathic toxins
Allelopathic toxins are compounds produced by plants that inhibit the growth of other plants. The classic example of allelopathy is found in the black walnut (Juglans nigra). It produces juglone and juglonic acid, which inhibit the growth of many plants. Fresh wood chips from black walnut should not be used as mulch unless well composted. Other allelopathic mulches include uncomposted sawdust of redwood (Sequoia) and cedar (Cedrus) and the bark of spruce (Picea), larch (Larix), and Douglas fir (Pseudotsuga).
Excessive Mulch
Excessive use of piled mulch such as "volcanoes", which are inverted cones of mulch creeping up the trunks of trees, can induce fermentation, immobilize nutrients, increase the amount of moisture next to the trunk, cut off the oxygen supply, and kill trees. The application of an excessive layer of mulch is common where mulch is used decoratively around a tree. Tree roots, in an effort to find more oxygen, will commonly grow above the soil surface into the mulch. This makes those roots more susceptible to drought, temperature extremes, frost heaving, and bark abrasion especially if using inorganic mulches. Trees that have been wounded on the stem are predisposed to stem canker pathogens if the mulch is covering the wound. Trees are prone to form adventitious roots that develop into stem girdling roots. These effects of over-mulching are not immediately observed. It may take a few years for the affects to be noticed.
Keep mulch from touching tree trunks and shrub stems. A rule of thumb is 3 to 5 inches (8 – 12 cm) away from young plants, and 8 to 12 inches (20 – 30 cm) away from mature tree trunks.
Root Suffocation
Suffocation of roots is the most common cause of death from over-mulching. Excessive mulch can contribute to a waterlogged root zone. With water occupying most soil pore space, air content is minimal and diffusion of oxygen is blocked. When soil oxygen levels drop below 10%, root growth declines. Oxygen starvation is especially common in the spring, autumn, during wet periods, and in soils that do not have good drainage.
Bark Death
Inner bark death comes from these volcanoes because the trunk tissue is quite different from root tissue and cannot survive in a continually moist environment. This also occurs when trees are installed too deep and the flare is buried. Most diseases require moisture to reproduce and spread. Trunk diseases gain a foothold in the moist, decaying bark tissue under the mulch. The disease organisms ultimately invade the inner bark, disrupting food transport and finally killing the plant. This is compounded by the presence of bark beetles and borers.
Wet mulch layers piled up next to the trunk may begin to heat up when the mulch begins to decompose (similar to composting), where temperatures may reach 120° – 140° F (50° – 60°C). This high heat level may kill the inner bark of young trees and prevent the hardening-off period, causing the tissue to die.
Rodents
Piles of mulch next to the trunk may also provide cover for chewing rodents. These rodents live in the warm mulch and chew on the nutritious inner bark. This often goes unnoticed until spring when the tree is dead. If the trunk is chewed over 50%, there is little that can be done to save it except for bridge grafting.
Solution
If mulch volcanoes are observed in the landscape, pull them down and away from the stems and spread them out over a larger area.
Protecting Trees from Winter Damage
Proper winter care begins in the summer. Trees take advantage of the autumn and early winter to build reserves for supporting life functions during winter dormancy.
Fertilizer
A fertilization regimen in the autumn can help prepare trees for spring. Many arborists and landscape architects recommend a slow-release fertilizer after plants have gone dormant following a good hard freeze. Autumn fertilization with an effective slow-release fertilizer is great preventative maintenance for nutrient-deficient, high-value trees. Avoid using fertilizers with highly available nitrogen after July because it can force too much new growth at the wrong time of year.
Water
Watering can be decreased in early autumn to promote dormancy and increased in late autumn to provide the water needed to withstand the drying winds of winter just prior to the soil freezing.
Mulch
Assist trees by mulching to retain moisture and to insulate roots from the temperature extremes of winter.
Cold Temperature
Plants that are not hardy will be killed during the winter unless protected. Injury is more severe when low temperatures occur in early autumn or late spring, when there is little snow cover, or when low temperatures are prolonged.
Sunscald
Sunscald or cracked areas of dead bark usually occur on the south side of the trunk. On cold winter days, the sun can heat the bark and when the sun is blocked or sets, the bark temperature drops rapidly, freezing and killing tissues just under the bark. Young and thin-barked trees (cherry, birch, crabapple, honey locust, linden, maple, mountain ash, plum) are most susceptible for one year after installation. Trees that have been pruned or transplanted from a shady location are also sensitive. Thicker bark will insulate tissue from the sun’s heat ensuring it will remain dormant. Wrapping the trunk with a white tree wrap or other material can prevent sunscald. The wrap will reflect the sun and keep the bark at a constant temperature. Sometimes a wide, tall board set in front of the trunk will provide sufficient sun protection and it is easily removed in the spring. Remove the wrap in the spring after the last frost.
Dieback
Little can be done to protect deciduous plants that incur shoot dieback and bud death during winter. Plants that are marginally hardy should be installed in sheltered locations and those in a vigorous growing condition in the autumn are most likely to suffer winter dieback on the tender new growth. Avoid late summer pruning, fertilizing, and over watering.
Root Injury
Roots do not become dormant quickly and are less hardy than stems. Roots of most trees and shrubs are killed at temperatures at or below 0° to +10°F (– 18° to – 9° C). Plants survive because soil temperatures are much higher than air temperatures. Snow cover, mulch, and moist soil hold more heat than dry soil. Cracks in the installation backfill will allow cold air to penetrate into the root zone, reducing autumn root growth, or killing newly formed roots. They should be filled. New trees and shrubs should be mulched with wood chips or straw. If the autumn has been dry, water heavily before the ground freezes to reduce frost penetration.
Frost Heaving
Repeated freezing and thawing of soil causes expansion and contraction, which can heave new plantings out of the ground. A layer of mulch will prevent this by maintaining more constant soil temperatures.
Snow and Ice Damage
Most trees are tolerant of ice storms, especially those that receive proper care and pruning. Prune to reduce the number of weak, dead, or diseased branches that can fall in a storm. Pruning also encourages proper branching structure.
A frequent cause of damage occurs during an ice event that has followed a major snowfall. The weight of the wet snow causes large branches of a tree to fail. Many trees will bend way over in an ice storm, but by spring, most have regained their upright stature. However, those that do not recover must be removed or modified with temporary cabling to pull the tree upright. Proper structural pruning, to eliminate multiple leaders and weak branch attachments must be done in early spring to reduce snow and ice damage. Other trees have disease problems that cause the tree to fail during ice events. Even without a storm, the same tree probably would die the following summer. Still others fail because they have weak wood. Often branches bend way over and snap even in the lightest snow. When the weight of ice is added, the whole tree can be destroyed.
The most common case of tree failure during ice storms occurs in trees with tight unions and in trees having too many branches coming from a common length of trunk. Attempts to correct this problem by careful pruning will sometimes work. A better solution is to avoid installing these trees in the first place.
Salt Damage
Salt spray can cause desiccation because the high concentration of salt draws water out of the root and into the soil. This causes a drought condition to occur in the tree. In desert regions, the lack of rainfall and evaporation in the soil will result in an accumulation of salt in the soil. Many trees can be disfigured and killed by salt (sodium chloride). The worst damage occurs to sensitive species installed near heavily salted roads, especially when they lie downhill or have poor drainage. Winter salt damage can be recognized by looking for "witch's brooms" (cluster of twigs growing out of branch ends) on deciduous trees or yellow tips on evergreen needles. In early summer look for marginal leaf scorch on deciduous trees. Look for yellow, brown or fallen needles on evergreens especially on the side toward the road.
Fortunately many trees will tolerate salt excesses. Well-drained soil is an important factor in reducing salt damage. Flooding the root zone with water should reverse the problem. Melting snow and spring rains will usually flush the salt lower into the soil profile. Reduce salt application rates by lowering the throwing distance of snowplows and salt applications to the streets before the roads freeze. Use less harmful ice melting products such as calcium chloride instead of sodium chloride and mix in inert materials like sand. Raise the installation site, or shelter the trees with a barrier so salt is easily leached away from trees.
Insects & Disease
Because plant disease and insect pests tend to linger from one season to the next, an important first step toward preparation for the coming growing season is the application of a dormant season spray. This activity should only be done if the situation warrants treatment. Apply dormant sprays or horticultural oil on trees in the early spring when the temperature is above 40° F (4° C). Evergreens should be sprayed before winter to kill as many insects and eggs as possible. Before spraying, make sure that plants are truly dormant to prevent devastating results.
Animal Damage
Rodents and deer can all cause severe damage to plants and trees in the winter. These animals feed on the tender twigs, bark, and foliage during the winter. They can girdle trees and shrubs and eat shrubs to the ground line. Trees can be protected from rodent damage by placing a cylinder of ¼ inch (0.6 cm) mesh hardware cloth around the trunk. The cylinder should extend 2 – 3 inches (5 – 7 cm) below the ground line for mice damage prevention and 18 – 24 inches (47 – 54 cm) above the anticipated snow line for rabbit damage prevention. Plastic tree guards and chicken wire are also effective. Deer feed on branches of small trees and shrubs. Deer can cause significant injury and breakage by rubbing their antlers on trees during the autumn. Deer can also be successfully deterred with fencing. To be effective, fences must be more than 6 feet (2 m) high and constructed properly. If deer are starving, there is little that will prevent feeding damage.
For many trees, repellents may be the best solution. The most effective repellents for rodents are those containing thiram, a common fungicide sprayed on trees and shrubs. Repeat applications are necessary after heavy precipitation. Commercial baits containing poisoned grain may be hazardous to humans, pets, and beneficial wildlife. Shelter or containerize baits so that they stay dry and are accessible only to targeted pests. Trapping and shooting, where legal, will also control wildlife.
Winter Discoloration of Evergreens
Browning or bleaching of evergreen foliage occurs because:
Foliar damage normally occurs on the south, southwest, and windward sides of the plant, but in severe cases the whole plant may be affected. Yew, arborvitae, and hemlock are most susceptible, but winter browning can affect all evergreens. New transplants or plants with succulent, late season growth are particularly sensitive.
Minimize winter injury by proper placement of evergreens in the landscape by not installing them on the south sides of buildings or in windy, sunny places. Also prop pine boughs against evergreens to protect them from wind and sun.
Winter injury can be prevented by constructing a barrier of burlap on the windward sides or surrounding the evergreen but leaving the top open to allow for air and light penetration. Never stress plants by under watering or over watering. Decrease watering slightly in September to encourage hardening off, and then water thoroughly in October until freeze-up. Anti-desiccant and anti-transpiration sprays are often recommended but studies have shown them to be ineffective.
If an evergreen has suffered winter injury, wait until mid-spring before pruning. Buds are more cold hardy than foliage and will often grow and fill in areas where brown foliage was removed. Prune dead branches back to living tissue. Fertilize injured plants in early spring and water them well throughout the season.
Proper winter care begins in the summer. Trees take advantage of the autumn and early winter to build reserves for supporting life functions during winter dormancy.
Fertilizer
A fertilization regimen in the autumn can help prepare trees for spring. Many arborists and landscape architects recommend a slow-release fertilizer after plants have gone dormant following a good hard freeze. Autumn fertilization with an effective slow-release fertilizer is great preventative maintenance for nutrient-deficient, high-value trees. Avoid using fertilizers with highly available nitrogen after July because it can force too much new growth at the wrong time of year.
Water
Watering can be decreased in early autumn to promote dormancy and increased in late autumn to provide the water needed to withstand the drying winds of winter just prior to the soil freezing.
Mulch
Assist trees by mulching to retain moisture and to insulate roots from the temperature extremes of winter.
Cold Temperature
Plants that are not hardy will be killed during the winter unless protected. Injury is more severe when low temperatures occur in early autumn or late spring, when there is little snow cover, or when low temperatures are prolonged.
Sunscald
Sunscald or cracked areas of dead bark usually occur on the south side of the trunk. On cold winter days, the sun can heat the bark and when the sun is blocked or sets, the bark temperature drops rapidly, freezing and killing tissues just under the bark. Young and thin-barked trees (cherry, birch, crabapple, honey locust, linden, maple, mountain ash, plum) are most susceptible for one year after installation. Trees that have been pruned or transplanted from a shady location are also sensitive. Thicker bark will insulate tissue from the sun’s heat ensuring it will remain dormant. Wrapping the trunk with a white tree wrap or other material can prevent sunscald. The wrap will reflect the sun and keep the bark at a constant temperature. Sometimes a wide, tall board set in front of the trunk will provide sufficient sun protection and it is easily removed in the spring. Remove the wrap in the spring after the last frost.
Dieback
Little can be done to protect deciduous plants that incur shoot dieback and bud death during winter. Plants that are marginally hardy should be installed in sheltered locations and those in a vigorous growing condition in the autumn are most likely to suffer winter dieback on the tender new growth. Avoid late summer pruning, fertilizing, and over watering.
Root Injury
Roots do not become dormant quickly and are less hardy than stems. Roots of most trees and shrubs are killed at temperatures at or below 0° to +10°F (– 18° to – 9° C). Plants survive because soil temperatures are much higher than air temperatures. Snow cover, mulch, and moist soil hold more heat than dry soil. Cracks in the installation backfill will allow cold air to penetrate into the root zone, reducing autumn root growth, or killing newly formed roots. They should be filled. New trees and shrubs should be mulched with wood chips or straw. If the autumn has been dry, water heavily before the ground freezes to reduce frost penetration.
Frost Heaving
Repeated freezing and thawing of soil causes expansion and contraction, which can heave new plantings out of the ground. A layer of mulch will prevent this by maintaining more constant soil temperatures.
Snow and Ice Damage
Most trees are tolerant of ice storms, especially those that receive proper care and pruning. Prune to reduce the number of weak, dead, or diseased branches that can fall in a storm. Pruning also encourages proper branching structure.
A frequent cause of damage occurs during an ice event that has followed a major snowfall. The weight of the wet snow causes large branches of a tree to fail. Many trees will bend way over in an ice storm, but by spring, most have regained their upright stature. However, those that do not recover must be removed or modified with temporary cabling to pull the tree upright. Proper structural pruning, to eliminate multiple leaders and weak branch attachments must be done in early spring to reduce snow and ice damage. Other trees have disease problems that cause the tree to fail during ice events. Even without a storm, the same tree probably would die the following summer. Still others fail because they have weak wood. Often branches bend way over and snap even in the lightest snow. When the weight of ice is added, the whole tree can be destroyed.
The most common case of tree failure during ice storms occurs in trees with tight unions and in trees having too many branches coming from a common length of trunk. Attempts to correct this problem by careful pruning will sometimes work. A better solution is to avoid installing these trees in the first place.
Salt Damage
Salt spray can cause desiccation because the high concentration of salt draws water out of the root and into the soil. This causes a drought condition to occur in the tree. In desert regions, the lack of rainfall and evaporation in the soil will result in an accumulation of salt in the soil. Many trees can be disfigured and killed by salt (sodium chloride). The worst damage occurs to sensitive species installed near heavily salted roads, especially when they lie downhill or have poor drainage. Winter salt damage can be recognized by looking for "witch's brooms" (cluster of twigs growing out of branch ends) on deciduous trees or yellow tips on evergreen needles. In early summer look for marginal leaf scorch on deciduous trees. Look for yellow, brown or fallen needles on evergreens especially on the side toward the road.
Fortunately many trees will tolerate salt excesses. Well-drained soil is an important factor in reducing salt damage. Flooding the root zone with water should reverse the problem. Melting snow and spring rains will usually flush the salt lower into the soil profile. Reduce salt application rates by lowering the throwing distance of snowplows and salt applications to the streets before the roads freeze. Use less harmful ice melting products such as calcium chloride instead of sodium chloride and mix in inert materials like sand. Raise the installation site, or shelter the trees with a barrier so salt is easily leached away from trees.
Insects & Disease
Because plant disease and insect pests tend to linger from one season to the next, an important first step toward preparation for the coming growing season is the application of a dormant season spray. This activity should only be done if the situation warrants treatment. Apply dormant sprays or horticultural oil on trees in the early spring when the temperature is above 40° F (4° C). Evergreens should be sprayed before winter to kill as many insects and eggs as possible. Before spraying, make sure that plants are truly dormant to prevent devastating results.
Animal Damage
Rodents and deer can all cause severe damage to plants and trees in the winter. These animals feed on the tender twigs, bark, and foliage during the winter. They can girdle trees and shrubs and eat shrubs to the ground line. Trees can be protected from rodent damage by placing a cylinder of ¼ inch (0.6 cm) mesh hardware cloth around the trunk. The cylinder should extend 2 – 3 inches (5 – 7 cm) below the ground line for mice damage prevention and 18 – 24 inches (47 – 54 cm) above the anticipated snow line for rabbit damage prevention. Plastic tree guards and chicken wire are also effective. Deer feed on branches of small trees and shrubs. Deer can cause significant injury and breakage by rubbing their antlers on trees during the autumn. Deer can also be successfully deterred with fencing. To be effective, fences must be more than 6 feet (2 m) high and constructed properly. If deer are starving, there is little that will prevent feeding damage.
For many trees, repellents may be the best solution. The most effective repellents for rodents are those containing thiram, a common fungicide sprayed on trees and shrubs. Repeat applications are necessary after heavy precipitation. Commercial baits containing poisoned grain may be hazardous to humans, pets, and beneficial wildlife. Shelter or containerize baits so that they stay dry and are accessible only to targeted pests. Trapping and shooting, where legal, will also control wildlife.
Winter Discoloration of Evergreens
Browning or bleaching of evergreen foliage occurs because:
- Winter sun and wind cause excessive transpiration while the roots are in frozen soil.
- Bright sunny days cause warming of tissue above; that in turn initiates cellular activity. Then, when the temperature drops the foliage is injured or killed.
- During bright, cold winter days, chlorophyll in the foliage is destroyed and is not re-synthesized when temperatures are below 28° F (–2° C). This results in a bleaching of the foliage.
- Cold temperatures persist before plants have hardened off completely in the autumn, or late in the spring, after new growth has occurred, and it can result in injury or death of this tissue.
Foliar damage normally occurs on the south, southwest, and windward sides of the plant, but in severe cases the whole plant may be affected. Yew, arborvitae, and hemlock are most susceptible, but winter browning can affect all evergreens. New transplants or plants with succulent, late season growth are particularly sensitive.
Minimize winter injury by proper placement of evergreens in the landscape by not installing them on the south sides of buildings or in windy, sunny places. Also prop pine boughs against evergreens to protect them from wind and sun.
Winter injury can be prevented by constructing a barrier of burlap on the windward sides or surrounding the evergreen but leaving the top open to allow for air and light penetration. Never stress plants by under watering or over watering. Decrease watering slightly in September to encourage hardening off, and then water thoroughly in October until freeze-up. Anti-desiccant and anti-transpiration sprays are often recommended but studies have shown them to be ineffective.
If an evergreen has suffered winter injury, wait until mid-spring before pruning. Buds are more cold hardy than foliage and will often grow and fill in areas where brown foliage was removed. Prune dead branches back to living tissue. Fertilize injured plants in early spring and water them well throughout the season.
Improve Tree Performance at Installation Time
Improving a tree’s performance in the landscape requires attention to many different potential problems. It is preferable that the freshly delivered trees be installed as soon as possible. However, very often trees are delivered a few weeks prior to the scheduled installation date. During this period the trees must be properly stored and monitored to ensure survival and a vigorous root response after final installation. The roots and root balls should never be allowed to dry out. Listed below are some typical problems and the best solution to that problem.
Poor Roots
Poor root systems are the result of several problems including poor installation procedures and root-bound containers. Bare root trees, for example, lose all their fine-fibrous roots during harvest and storage. New roots are produced during the spring bud swell, but these new roots often dehydrate during storage and installation if the care is not good and the roots are allowed to dry out.
Many young trees have their roots buried by cultivation at the nursery. Liners installed with a planting machine will often have roots spreading only in the direction of the planting trench because the soil was compacted by the planter wheels. Other trees have their roots cut too close to the trunk by a tree spade. Liners installed from conventional containers are often root bound or have other root deformities.
Solution
Install trees with good, dense root systems. Wash all soil from the roots so that upon inspection, trees with circling or deformed roots can be rejected.
Small Root Balls
Tree roots are often buried by cultivators during nursery maintenance. When this happens the surface soil covers the flare and when the trees are dug to their typical depth, fewer roots are taken with the tree than if the soil covering the flare was removed before the trees were dug. For example, if the tree had 6 inches of soil piled on top of the trunk flare and the tree was dug to its conventional 18 inches deep, the actual area of roots would only be 12 inches deep; so far fewer roots would be dug with the tree and that would not be desirable. Trees are sometimes intentionally dug with root balls too small to sustain the top of the tree for more than a brief period. The most frequent reasons for this are to reduce weight during shipping, to sell the tree for less cost, and to avoid the loss of good field soil. (Another good reason to purchase trees bare root.)
Solution
Inspect the root ball and locate the flare at the point of picking up the tree. Reject all undersized root balls after the flare is located.
Poor Nutrition
Trees need the sugars produced by their leaves. When fertilizer in the soil is low and the plants are harvested, any limited nutrition in the roots will be quickly exhausted. When the energy reserves decline in the root ball, the rate of root production also declines. Nutrition must also be ample to provide for root growth during the winter months.
Solutions
Root Growth in Mulch
After digging, most B&B trees have root buds and energy to make one good flush of new roots. If the tree has not been installed, then that root flush might extend into the mulch that surrounds the root ball in storage. When the trees are then moved to a planting hole, the roots that have extended into the mulch are lost due to breakage, dehydration or both. Root production must then start over with the tree in a much weaker condition. The few roots that are produced following installation must sustain the tree, including bud development.
Solutions
Poor Quality Mulch
Fresh hardwood bark or wood chips make very poor mulch in the storage area. The small particles decompose quickly and tie up any nitrogen present, making it unavailable for the tree. Hardwood chips also release substantial concentrations of calcium and manganese. Unfortunately, high levels of manganese are toxic and cause leaf chlorosis and browning of leaf margins.
Solution
Conifer bark is better for mulch in the storage area and does not accumulate calcium, manganese, and other elements like hardwood mulch does.
Poor Water Management
Water management of a B&B tree is challenging because of the contrast between the field soil in the ball and the coarse mulch that surrounds the root ball in storage. The mulch allows rapid penetration of water which flows to the ground beneath the tree. The root ball soils absorb water at a much slower rate. When leaves are present, water in the root ball is typically used up in a day or less.
Solution
When watering the root ball, it should be done very slowly. For example, one gallon of water should be applied during a period of 30 to 60 minutes. Applying that gallon of water in 5 minutes will mean that most of the water has run off the ball and not soaked into it.
Poor Drainage
Many tree storage areas are poorly drained due to soil compaction, spillage of soil and mulch materials, and the grinding of soil into very small particles by equipment tires. Water is often applied by large sprinklers and the water can not run off in a timely fashion. Many trees such as redbud, dogwood, and most conifers, can not tolerate this excess water.
Solutions
Trees Held Too Long
The longer a tree is held under adverse conditions, the greater the problems that develop and the less likely it will be that the tree will survive and thrive after it is installed at its permanent location.
Solution
If B&B trees are going to be stored for long periods of time, they should be transplanted into containers that encourage the development of fibrous roots. That way, when the trees are installed they will be better able to deal with the transplanting shock.
Bare Root Trees
The care of bare root trees in storage is completely different. The roots of these trees should be stored in pea gravel or wood chip mulch and kept frequently watered. The tops of the trees may need anchoring to prevent blow down in windy locations. If the roots are kept moist every second from the time they are dug and kept in the
storage area until they are covered with soil at the final location, there should be very little transplant shock.
Improving a tree’s performance in the landscape requires attention to many different potential problems. It is preferable that the freshly delivered trees be installed as soon as possible. However, very often trees are delivered a few weeks prior to the scheduled installation date. During this period the trees must be properly stored and monitored to ensure survival and a vigorous root response after final installation. The roots and root balls should never be allowed to dry out. Listed below are some typical problems and the best solution to that problem.
Poor Roots
Poor root systems are the result of several problems including poor installation procedures and root-bound containers. Bare root trees, for example, lose all their fine-fibrous roots during harvest and storage. New roots are produced during the spring bud swell, but these new roots often dehydrate during storage and installation if the care is not good and the roots are allowed to dry out.
Many young trees have their roots buried by cultivation at the nursery. Liners installed with a planting machine will often have roots spreading only in the direction of the planting trench because the soil was compacted by the planter wheels. Other trees have their roots cut too close to the trunk by a tree spade. Liners installed from conventional containers are often root bound or have other root deformities.
Solution
Install trees with good, dense root systems. Wash all soil from the roots so that upon inspection, trees with circling or deformed roots can be rejected.
Small Root Balls
Tree roots are often buried by cultivators during nursery maintenance. When this happens the surface soil covers the flare and when the trees are dug to their typical depth, fewer roots are taken with the tree than if the soil covering the flare was removed before the trees were dug. For example, if the tree had 6 inches of soil piled on top of the trunk flare and the tree was dug to its conventional 18 inches deep, the actual area of roots would only be 12 inches deep; so far fewer roots would be dug with the tree and that would not be desirable. Trees are sometimes intentionally dug with root balls too small to sustain the top of the tree for more than a brief period. The most frequent reasons for this are to reduce weight during shipping, to sell the tree for less cost, and to avoid the loss of good field soil. (Another good reason to purchase trees bare root.)
Solution
Inspect the root ball and locate the flare at the point of picking up the tree. Reject all undersized root balls after the flare is located.
Poor Nutrition
Trees need the sugars produced by their leaves. When fertilizer in the soil is low and the plants are harvested, any limited nutrition in the roots will be quickly exhausted. When the energy reserves decline in the root ball, the rate of root production also declines. Nutrition must also be ample to provide for root growth during the winter months.
Solutions
- Trees should be dug at the proper time so stored sugars are not needed immediately. This is usually in the autumn going into dormancy or in the spring, before bud break.
- Fertilizer should be added to root balls that have not been installed soon after digging.
Root Growth in Mulch
After digging, most B&B trees have root buds and energy to make one good flush of new roots. If the tree has not been installed, then that root flush might extend into the mulch that surrounds the root ball in storage. When the trees are then moved to a planting hole, the roots that have extended into the mulch are lost due to breakage, dehydration or both. Root production must then start over with the tree in a much weaker condition. The few roots that are produced following installation must sustain the tree, including bud development.
Solutions
- Keep mulch use to a minimum or not at all if the tree will be installed in less than one week.
- If the tree is going to be stored for more than a week, make a plan to save and protect the new roots in mulch in the storage area and at the job site.
- Another time when mulch should be used on B&B trees is to protect the root balls from cold injury. Roots are more sensitive to cold temperatures than tree tops. Several studies determined the level of cold at which tree roots are damaged. Generally this is around 15° F (-10° C), depending on the species. Below this temperature, the roots die. Root balls not mulched can reach this temperature an inch or more from the root ball surface when the air temperature is 10° F (-12° C) or lower overnight.
- Remove all mulch from B&B trees before the spring growth begins. When the buds swell in spring, the tree roots begin to grow and will grow into the mulch if it is still present. Without the mulch around the root ball, tree roots will still begin to grow, but the root growth will occur within the root ball, and a healthier, more fibrous root system will develop.
- It is better to heel the tree into soil instead of on the surface and covered with mulch.
Poor Quality Mulch
Fresh hardwood bark or wood chips make very poor mulch in the storage area. The small particles decompose quickly and tie up any nitrogen present, making it unavailable for the tree. Hardwood chips also release substantial concentrations of calcium and manganese. Unfortunately, high levels of manganese are toxic and cause leaf chlorosis and browning of leaf margins.
Solution
Conifer bark is better for mulch in the storage area and does not accumulate calcium, manganese, and other elements like hardwood mulch does.
Poor Water Management
Water management of a B&B tree is challenging because of the contrast between the field soil in the ball and the coarse mulch that surrounds the root ball in storage. The mulch allows rapid penetration of water which flows to the ground beneath the tree. The root ball soils absorb water at a much slower rate. When leaves are present, water in the root ball is typically used up in a day or less.
Solution
When watering the root ball, it should be done very slowly. For example, one gallon of water should be applied during a period of 30 to 60 minutes. Applying that gallon of water in 5 minutes will mean that most of the water has run off the ball and not soaked into it.
Poor Drainage
Many tree storage areas are poorly drained due to soil compaction, spillage of soil and mulch materials, and the grinding of soil into very small particles by equipment tires. Water is often applied by large sprinklers and the water can not run off in a timely fashion. Many trees such as redbud, dogwood, and most conifers, can not tolerate this excess water.
Solutions
- Watering the root ball should be done very slowly, preferably with a water bag dripping all day long.
- Long term storage areas should have good surface drainage and not be mulched.
Trees Held Too Long
The longer a tree is held under adverse conditions, the greater the problems that develop and the less likely it will be that the tree will survive and thrive after it is installed at its permanent location.
Solution
If B&B trees are going to be stored for long periods of time, they should be transplanted into containers that encourage the development of fibrous roots. That way, when the trees are installed they will be better able to deal with the transplanting shock.
Bare Root Trees
The care of bare root trees in storage is completely different. The roots of these trees should be stored in pea gravel or wood chip mulch and kept frequently watered. The tops of the trees may need anchoring to prevent blow down in windy locations. If the roots are kept moist every second from the time they are dug and kept in the
storage area until they are covered with soil at the final location, there should be very little transplant shock.
Watering Established Trees
Water plays many key roles in the lives of trees. The amount of water a soil can hold following the drainage of water due to the force of gravity is called field capacity. The tree root takes in water at and below field capacity until it reaches the permanent wilting point. When water is between field capacity and the wilting point, landscape plants function normally.
Watering Established Trees
The tree's roots are between 8 – 18 inches (20 – 45 cm) under the surface and they spread out to a radius that exceeds the height of the tree. In situations where grass is growing under the tree branches, the grass will out-compete a tree root for moisture, oxygen, and other nutrients. Therefore, trees should have their own irrigation system that will provide water at a slower rate over a longer period of time. Sprinkler heads should have low volume nozzles. Soaker hoses and drip irrigation are other options. This allows the water to penetrate at least 12 inches (30 cm) deep. Soil soakers tend not to soak in as deep and almost need to be left running overnight to adequately water a large tree. Sprinklers are the best because the spray will wash dirt and pollutants off the leaves; the spray will increase the humidity and lower the temperature; the system is easily checked for maintenance; and the water will easily soak into the mulch.
For the most part, trees can only take up water from soil in proximity to the roots. Established trees are in contact with greater volumes of soil due to wide-spreading root systems, and are more capable of obtaining water. Trees that have root systems severed to facilitate transplanting or construction have fewer roots and a smaller soil volume in contact with roots.
While irrigation maybe needed to get water to a tree, mulch is very useful in keeping the water in the soil. The mulch will reduce the amount of evaporation that occurs, while also keeping the soil temperature cooler and reducing the number of weeds competing for soil moisture. In a good year, with regular and adequate rainfall coupled with a layer of mulch over the tree’s root system, irrigation may never be necessary beyond the establishment period. However, rainfall is unpredictable.
In addition, soil texture, structure, and percolation influence the amount of water available to a tree. Trees growing on sandy soils will probably need irrigation more frequently, especially for larger trees in sunny, windy, and hot climates. Conversely, trees installed in clayey soils that do not percolate adequately require less irrigation. In fact, frequent irrigation may do harm by displacing essential soil oxygen.
Examine the soil moisture 4-8 inches (10-20 cm) deep to determine the need for water. If the soil feels dry or just slightly damp, watering is needed. A slow trickle of the garden hose at the base of the plant until the soil is thoroughly soaked is the best method. Short, frequent watering should be avoided as this promotes the development of a shallow root system that is vulnerable to various environmental stresses.
Watering should occur when less than an inch of rain has fallen in a two-week period and temperature has passed 85° F (30° C). While the soil surface is drying out, deep moisture concentrations are attracting roots. The end result is less root death due to temperature extremes. Additionally, root growth increases at lower soil levels since soil temperatures are cooler at twelve or more inches deep.
Water is essential for the tree to manufacture food. Water dissolves fertilizer salts that can then be absorbed by the roots. It also acts as a coolant by evaporation through the leaves, keeping the tree from overheating on summer days. Finally, water serves as a system for transporting nutrients and hormones throughout the tree and being a part of biochemical reactions within the tree. Symptoms of water stress include wilting and loss of leaves. Branches may also bend during periods of extreme drought.
Most of the tree roots that absorb water, called feeder roots, are within the top fifteen inches of soil. These roots are generally congregated under the outer branches of the tree. Mature trees may have feeder roots extending 50 feet (15 m) past the drip line. Few water absorbing roots are under the plant’s canopy or near the trunk. Feeder roots are not large. Most are finer than a strand of hair. They are easily severed when digging or can dry out during droughts. On the other hand, they are easily replaced.
Recycled Water
The use of recycled water from sewage treatment plants is often a poorer quality than potable water and is therefore unsuitable for use in landscapes. The recycled water often contains high levels of salts and nutrient ions that are detrimental to tree growth. The use of recycled water should only be considered if the plants will tolerate salt, boron, and other chemicals found in this water. The use of this water also requires a long-term effort to monitor plant health and soil chemical changes. Drainage is also especially critical for plant survival.
Wetting Agents
The molecular structure of water provides a strong attachment to the soil's pore space between the grains of soil. This attachment makes the water and molecules clump together rather than spread out through the soil. Boundaries of soil appear at the surface, so water does not soak into the soil very quickly. Boundaries also occur between the root ball and parent soil of a newly installed tree, or between the topsoil and other layers of subsoil. Wetting agents are materials that make the water molecules less attractive to each other so these molecules move more quickly through the soil pores and move effectively through any boundaries of soil. The soil microbes will also use the wetting agent as an additional food source.
Wetting agents should not be considered a substitute for other soil preparation or maintenance needs. It only makes water wetter, hence more easily absorbed by the plant's roots. Wetting agents do not change a plant's water needs either. One inch of water per week is required, with or without wetting agents. Management practices such as topdressing, mulch, compaction management, etc. should continue.
Wetting agents must be applied according to the manufacturer's instructions. Abuse by overdosing can cause harm to the soil and to the plant's root system. Wetting agents are most effective for relieving extremely dry soil. Using this material for routine watering is a waste of the product. Wetting agents can be purchased from a horticulture or arboriculture supply house, or can be a dish-washing detergent.
Frequency of Irrigation
The amount and frequency of irrigation really depends on several environmental, soil, and plant characteristics. In general:
Too Much Water
Plants may wilt if there is too much water in the soil because the oxygen and gas exchange is blocked. Plants may also wilt because of soil compaction or diseases that affect cell membranes.
Antitranspirants
Antitranspirants (also known as anti-desiccants) have also been suggested to aid transplant success. Antitranspirants reduce water loss through stomates by either causing stomate closure or covering stomates with a waxy film that is a barrier to water loss. In theory antitranspirants seem reasonable, but in practice they may lengthen the establishment period. While closed or blocked stomates reduce water loss, they also decrease carbon dioxide entry into leaves. Less carbon dioxide accordingly reduces the manufacture of energy compounds from photosynthesis.
Water plays many key roles in the lives of trees. The amount of water a soil can hold following the drainage of water due to the force of gravity is called field capacity. The tree root takes in water at and below field capacity until it reaches the permanent wilting point. When water is between field capacity and the wilting point, landscape plants function normally.
Watering Established Trees
The tree's roots are between 8 – 18 inches (20 – 45 cm) under the surface and they spread out to a radius that exceeds the height of the tree. In situations where grass is growing under the tree branches, the grass will out-compete a tree root for moisture, oxygen, and other nutrients. Therefore, trees should have their own irrigation system that will provide water at a slower rate over a longer period of time. Sprinkler heads should have low volume nozzles. Soaker hoses and drip irrigation are other options. This allows the water to penetrate at least 12 inches (30 cm) deep. Soil soakers tend not to soak in as deep and almost need to be left running overnight to adequately water a large tree. Sprinklers are the best because the spray will wash dirt and pollutants off the leaves; the spray will increase the humidity and lower the temperature; the system is easily checked for maintenance; and the water will easily soak into the mulch.
For the most part, trees can only take up water from soil in proximity to the roots. Established trees are in contact with greater volumes of soil due to wide-spreading root systems, and are more capable of obtaining water. Trees that have root systems severed to facilitate transplanting or construction have fewer roots and a smaller soil volume in contact with roots.
While irrigation maybe needed to get water to a tree, mulch is very useful in keeping the water in the soil. The mulch will reduce the amount of evaporation that occurs, while also keeping the soil temperature cooler and reducing the number of weeds competing for soil moisture. In a good year, with regular and adequate rainfall coupled with a layer of mulch over the tree’s root system, irrigation may never be necessary beyond the establishment period. However, rainfall is unpredictable.
In addition, soil texture, structure, and percolation influence the amount of water available to a tree. Trees growing on sandy soils will probably need irrigation more frequently, especially for larger trees in sunny, windy, and hot climates. Conversely, trees installed in clayey soils that do not percolate adequately require less irrigation. In fact, frequent irrigation may do harm by displacing essential soil oxygen.
Examine the soil moisture 4-8 inches (10-20 cm) deep to determine the need for water. If the soil feels dry or just slightly damp, watering is needed. A slow trickle of the garden hose at the base of the plant until the soil is thoroughly soaked is the best method. Short, frequent watering should be avoided as this promotes the development of a shallow root system that is vulnerable to various environmental stresses.
Watering should occur when less than an inch of rain has fallen in a two-week period and temperature has passed 85° F (30° C). While the soil surface is drying out, deep moisture concentrations are attracting roots. The end result is less root death due to temperature extremes. Additionally, root growth increases at lower soil levels since soil temperatures are cooler at twelve or more inches deep.
Water is essential for the tree to manufacture food. Water dissolves fertilizer salts that can then be absorbed by the roots. It also acts as a coolant by evaporation through the leaves, keeping the tree from overheating on summer days. Finally, water serves as a system for transporting nutrients and hormones throughout the tree and being a part of biochemical reactions within the tree. Symptoms of water stress include wilting and loss of leaves. Branches may also bend during periods of extreme drought.
Most of the tree roots that absorb water, called feeder roots, are within the top fifteen inches of soil. These roots are generally congregated under the outer branches of the tree. Mature trees may have feeder roots extending 50 feet (15 m) past the drip line. Few water absorbing roots are under the plant’s canopy or near the trunk. Feeder roots are not large. Most are finer than a strand of hair. They are easily severed when digging or can dry out during droughts. On the other hand, they are easily replaced.
Recycled Water
The use of recycled water from sewage treatment plants is often a poorer quality than potable water and is therefore unsuitable for use in landscapes. The recycled water often contains high levels of salts and nutrient ions that are detrimental to tree growth. The use of recycled water should only be considered if the plants will tolerate salt, boron, and other chemicals found in this water. The use of this water also requires a long-term effort to monitor plant health and soil chemical changes. Drainage is also especially critical for plant survival.
Wetting Agents
The molecular structure of water provides a strong attachment to the soil's pore space between the grains of soil. This attachment makes the water and molecules clump together rather than spread out through the soil. Boundaries of soil appear at the surface, so water does not soak into the soil very quickly. Boundaries also occur between the root ball and parent soil of a newly installed tree, or between the topsoil and other layers of subsoil. Wetting agents are materials that make the water molecules less attractive to each other so these molecules move more quickly through the soil pores and move effectively through any boundaries of soil. The soil microbes will also use the wetting agent as an additional food source.
Wetting agents should not be considered a substitute for other soil preparation or maintenance needs. It only makes water wetter, hence more easily absorbed by the plant's roots. Wetting agents do not change a plant's water needs either. One inch of water per week is required, with or without wetting agents. Management practices such as topdressing, mulch, compaction management, etc. should continue.
Wetting agents must be applied according to the manufacturer's instructions. Abuse by overdosing can cause harm to the soil and to the plant's root system. Wetting agents are most effective for relieving extremely dry soil. Using this material for routine watering is a waste of the product. Wetting agents can be purchased from a horticulture or arboriculture supply house, or can be a dish-washing detergent.
Frequency of Irrigation
The amount and frequency of irrigation really depends on several environmental, soil, and plant characteristics. In general:
- supplemental irrigation is rarely needed during rainy periods,
- the need for irrigation increases with increasing temperature,
- windy conditions may necessitate more frequent irrigation,
- poorly drained, clay-type soils require less frequent irrigation than sandy soils,
- plants with small or poorly developed root systems are particularly sensitive to moisture deficits,
- newly installed trees and shrubs rely heavily on ample soil moisture in the root area throughout the first
growing season, - root growth is slowed or will stop completely in soils that are too wet or too dry,
- until the roots of newly installed trees begin to grow into the backfill, moisture available to the plant can be depleted very quickly.
Too Much Water
Plants may wilt if there is too much water in the soil because the oxygen and gas exchange is blocked. Plants may also wilt because of soil compaction or diseases that affect cell membranes.
Antitranspirants
Antitranspirants (also known as anti-desiccants) have also been suggested to aid transplant success. Antitranspirants reduce water loss through stomates by either causing stomate closure or covering stomates with a waxy film that is a barrier to water loss. In theory antitranspirants seem reasonable, but in practice they may lengthen the establishment period. While closed or blocked stomates reduce water loss, they also decrease carbon dioxide entry into leaves. Less carbon dioxide accordingly reduces the manufacture of energy compounds from photosynthesis.
Dealing with Drought
By Gordon Mann
Trees provide so many benefits and amenities like clean air, energy conservation, ambient temperature reduction, and sun protection. Trees are also one of the best investments in times of low water availability.
Water Runoff Challenges
In contrast to trees, most lawns and many shrubs require water over their entire root systems to stay viable. Lawns use more water than any other element of the landscape. Water falling on sloped landscapes tends to run off faster than it soaks in. Water runoff often discharges directly into gutters and storm drains, then moves to streams, lakes, and rivers. This water frequently contains fertilizers, pesticides, and other pollutants. Improving water retention practices has greater gains than just conservation. It includes higher water quality and better tree health.
Water Tips for Home and Work
The following are some best management practices for responding to water resource challenges during reduced water availability:
Estimated Faucet/hose = Leakage Rates (# of drips)
60 drops/minute = 192 gallons(572 liters)/month
90 drops/minute = 210 gallons(583 liters)/month
120 drops/minute = 429 gallons(1650 liters)/month
Watering tip for estimating the amount of water a tree needs per week:
Along with landscape water improvements, there are many other ways to reduce water use that will provide water capacity for landscapes.
Installing Trees During a Drought
Installing trees during times of drought and water restrictions should continue with caution. An understanding of the risks and consideration of proper maintenance activities to establish trees during these periods is crucial.
Why Install Trees During a Drought?
Installing trees and shrubs during drought can be risky. Watering restrictions are in place and establishing trees in a semi-arid region is difficult enough without an extended drought to contend with. However, by eliminating all tree installations we are missing many opportunities to sustain our urban forest. It is critical to not only have a diverse set 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, especially during times of drought, to replace trees that will be lost to age, injury 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.
Editor's note: The use of trade names in this article is meant for the convenience of the reader and does not constitute an endorsement or approval of any product to the exclusion of others.
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, Tree Worker Specialist, Utility Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA management 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.
By Gordon Mann
Trees provide so many benefits and amenities like clean air, energy conservation, ambient temperature reduction, and sun protection. Trees are also one of the best investments in times of low water availability.
- They need to be regularly watered in a limited area for the first three years of growth or until they become established and the root system develops to where it can obtain water from the soil. Most trees require very little irrigation water after establishment.
- Plant growth and decomposition provide organic matter to the soil, which will improve soil infiltration and
water holding capacity to 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. - Other trees growing in shaded areas require less water.
- Trees (after establishment) do not require their entire root system to receive water in order to survive. Comparatively, trees require less water per canopy area than landscape shrubs, flowers, and turf.
Water Runoff Challenges
In contrast to trees, most lawns and many shrubs require water over their entire root systems to stay viable. Lawns use more water than any other element of the landscape. Water falling on sloped landscapes tends to run off faster than it soaks in. Water runoff often discharges directly into gutters and storm drains, then moves to streams, lakes, and rivers. This water frequently contains fertilizers, pesticides, and other pollutants. Improving water retention practices has greater gains than just conservation. It includes higher water quality and better tree health.
Water Tips for Home and Work
The following are some best management practices for responding to water resource challenges during reduced water availability:
- Deeply soak trees and shrubs only after they show initial signs of water stress, and apply water in the morning or evening during off-peak use hours (between 9 pm and 9 am) to prevent excessive evaporation.
- Use a drip emitter, soaker hose, targeted bubbler, or other low-flow garden hose to direct water to the trees, and allow the water to slowly seep deep into the soil. A slow trickle is the most effective method for absorption. Watering with a hose at high speed usually results in run-off.
- 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.
- 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 runoff can provide non-potable water to irrigate trees.
- Cover bare soil with mulch to retain more soil moisture. Irrigation should be set so it wets the soil under the mulch.
- Remove weeds from flower and vegetable gardens as they begin to appear. Weeds are notorious for
stealing water away from desirable trees. - Use cultural practices such as such as mowing lawns higher and controlling water runoff on slopes will also help.
- Lawns are typically watered several times a week in hot weather, when one longer watering will be sufficient. Trees and shrubs require watering less frequently 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 tree needs.
- Add hydrogels to 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.
- Collect cold water from the sink or shower while waiting for the hot water to arrive.
- "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 the tree during a drought or water rationing restriction.
- Install a separate landscape water meter for monitoring water use and leak detection.
Estimated Faucet/hose = Leakage Rates (# of drips)
60 drops/minute = 192 gallons(572 liters)/month
90 drops/minute = 210 gallons(583 liters)/month
120 drops/minute = 429 gallons(1650 liters)/month
Watering tip for estimating the amount of water a tree needs per week:
- The tree needs 5 gallons (19 liters) plus 5 gallons for each inch of dbh. 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.
Along with landscape water improvements, 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.
- Use an automatic shutoff nozzle when washing cars or go to a water recycling car wash.
- Check pool and equipment for water leaks.
- Cover swimming pools to reduce evaporation.
Installing Trees During a Drought
Installing trees during times of drought and water restrictions should continue with caution. An understanding of the risks and consideration of proper maintenance activities 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.
- Keep trees in the landscape to reduce soil erosion, stabilize soils, significantly reduce storm water runoff, and shade 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.
- 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 investment risk of installing during drought periods. Plus the smaller tree can establish more quickly than installing a larger tree and it will also require less maintenance over time.
- Select trees from species that are hardy to the region and fit well with the periscope 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 Install Trees During a Drought?
Installing trees and shrubs during drought can be risky. Watering restrictions are in place and establishing trees in a semi-arid region is difficult enough without an extended drought to contend with. However, by eliminating all tree installations we are missing many opportunities to sustain our urban forest. It is critical to not only have a diverse set 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, especially during times of drought, to replace trees that will be lost to age, injury 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.
Editor's note: The use of trade names in this article is meant for the convenience of the reader and does not constitute an endorsement or approval of any product to the exclusion of others.
Sources
- Appleton, Bonnie Lee, "To Stake or Not to Stake?", Landscape Architecture, April 2004.
- "Basic Tree Biology", City Trees, The Journal of The Society of Municipal Arborists Vol. 37, Number 6 November/December 2001.
- Clatterbuck, Wayne K, "Post-Planting Tree Care: Fallacies and Recommendations", Wildlife & Fisheries Agricultural Extension Service, The University of Tennessee.
- Del Tredici, Peter, "Mulch", City Trees, The Journal of The Society of Municipal Arborists Vol. 36, Number 6 Nov/Dec 2000.
- Denver Water Co. "Planting Trees and Shrubs in Times of Drought and Water Restrictions", 2009.
- Dunwell, Winston C. and Robert E. McNeil, "Over Wintering Nursery Crops", University of Kentucky, College of Agriculture, 2005.
- Gilman, Edward F., "Planting Trees in Landscapes", Environmental Horticulture Department, IFAS, University of Florida, 2004.
- Gilman, E.F., R.J. Black, and B. Dehgan, “Irrigation volume and frequency and tree size affect
establishment rate”, Journal of Arboriculture 24(1):1-9. 1998. - Hauer, Rich, "Too much Mulch is Not a Good Thing!", Minnesota Department of Agriculture, 2001.
- Jin, Zhenfu, Byung Yeoup Chung, Kenji Iiyama, and Satomi Watanabe, "Components of Leaf Litter during Mulching", Journal of Arboriculture, July 2002.
- Johnson, Gary, “Establishing New Trees", University of Minnesota, Department of Forestry, 2010.
- Keslick and Son, "Technical Tree Biology Dictionary", Modern Arboriculture Associates, 2008.
- King, John, "Staking versus Tree Staples", City Trees, Vol. 38, Number 6 November/December
2002. - King, John, "How to Stabilize Newly Planted Trees", City Trees, Vol. 40, Number 1 January/February 2004.
- Krause, Charles, "Root Hardiness and Influence of DNA Herbicides in Over-wintered Containers", USDSA Research project, Funded FY 2004 Research, 2003 – 2008.
- Marzalina, E. Philip, M. and P.N. Avadhani, "Recovery Patterns Of Transplanted Trees", Arboricultural Journal 2002.
- Miller, Robert S., "Bare Root Tree Planting Advantages", City Trees, Vol. 39, Number 5 September/October 2003.
- Quinn, W., “Should Newly Planted Trees Be Staked and Tied?” ANLA Memorandum, Purdue University Extension Service, June 21, 2002.
- Pickering, J. S. and A. Sheperd, “Organic Landscape Mulches", Arboricultural Journal, 2000.
- Robinson, Lana, "Prep Trees Now for Growth Next Year", TCI Magazine, September 2003.
- Sacramento Tree Foundation, "Trees Are Great Especially During A Drought", 2008.
- Spafford, Anne, "Tree Staking and Guying", Landscape Architecture, November 2000.
- Struve. Daniel K. et. al., "Survival Of Transplanted Red Oaks", Journal of Arboriculture 26(3): 162-169.
- Trowbridge, Peter J. and Nina L. Bassuk, "Trees in the Urban Landscape", John Wiley & Sons, Inc. 2004.
- University of Minnesota Extension Service, "Protecting Trees & Shrubs Against Winter Damage", Advocate, Winter 2004.
- Watson, Gary W. and E. B. Himelick, "Principals and Practice of Planting Trees and Shrubs", International Society of Arboriculture, Savoy, IL 1997.
- Watson, G. and G. Himelick. “The Planting Basics”, American Nurseryman 187(10):40-44. 1998.
- Weicherding, Patrick, "Mulching Trees and Shrubs", University of Minnesota Extension Service - Andover, Minnesota. 2002.
- Whitcomb, Carl E., “Shrinkage can Destroy Profits”, Nursery Management & Production, September 2007.
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, Tree Worker Specialist, Utility Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA management 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.