#12 Read About Planning for a Greener Environment
Edited by Len Phillips, updated January 2023
Illustrated by Ethan Charles
Sections You may go directly to the section by clicking on titles listed here.
Edited by Len Phillips, updated January 2023
Illustrated by Ethan Charles
Sections You may go directly to the section by clicking on titles listed here.
Note: Click on green text in each section for more information and photos.
This topic is a collection of ideas that can be considered by municipal arborists and landscape architects in an attempt to assist the city with developing a greener environment. Some of the ideas are useful, but impractical in some cities, while others should be considered mandatory in every city. Additional information can be obtained by contacting the cities where examples have been provided. The list of sources at the end of this topic will also provide a place to look for more information.
This topic is a collection of ideas that can be considered by municipal arborists and landscape architects in an attempt to assist the city with developing a greener environment. Some of the ideas are useful, but impractical in some cities, while others should be considered mandatory in every city. Additional information can be obtained by contacting the cities where examples have been provided. The list of sources at the end of this topic will also provide a place to look for more information.
Sustainable Trees
What does "sustainability" mean when dealing with trees? Can trees be produced with an official sustainability label on them? In the near future, we may be asking nurseries to undergo a periodic review process to maintain their claim that they are using sustainable practices. The nursery industry has always been in the business of improving the environment. Millions of trees are grown each year to beautify our surroundings, fix carbon, create oxygen, and moderate temperatures. However, some ecological impact during the growing process is unavoidable, but nurseries can minimize their impact by using management techniques, sprays, fertilizers, and equipment that are all sustainable.
There is widespread confusion about sustainability that has arborists as well as nurseries believing that sustainability is all about using "organic" products and production methods or growing native trees only. While some growers feel that inorganic fertilizer and chemical use are not sustainable, others feel that it is the process that defines sustainability. Actually, sustainability requires leaving a small environmental footprint and using the most effective products in the most efficient manner.
A sustainable urban forestry program should include goals for all elements of the sustainability system such as vehicles, buildings, employees, tree species selection, tree placement and stabilization, soil volume characteristics, design guidelines, municipal code, green-gray infrastructure interface, solar access and building envelopes, waste stream, delivery stream, pruning rotation, etc. Sustainability does not mean trees must be native. All trees regardless of their origin can be sustainable if they meet the sustainability requirements. These details include selecting species to match site-specific environmental factors. This includes consideration to mature tree size, hardiness, urban tolerances, minimal insect and disease problems, nuisance fruit, soil conditions, biological activity, water holding capacity, and soil concerns. Soil concerns deal with compaction, fertility, microbial activity, and what needs to be done to meet any shortcomings. Also look at species diversification, proper installation, root stabilizing (if warranted), and irrigation requirements. Consideration should be given to pruning, maintenance, and future replacement. Do not overlook the importance of young tree care and preservation guidelines such as impacts of root pruning for sidewalk, curb, and gutter programs.
Bare Root Tree
The Process
Efficient sustainability can be achieved by the following:
Using products and labor efficiently is necessary as costs have risen in recent years. This may require inventive managers to discover new and efficient ways to apply products as well as effectively managing the trees growth.
For example, using root stabilizers instead of staking and guy wires, etc. saves time and money not only to purchase the product but to install it as well. Furthermore, the stabilizer does not need to ever be removed unless desired to recycle for a future installation. Metal stabilizers tend to be expensive but they are recyclable, while wood stabilizers are homemade for low cost, but never need to be removed.
Being pro-active is necessary when selecting and applying fertilizers or pesticides. For example, use a certain fertilizer or pesticide if it will save time and money in the long run. Fix insect and disease problems when first detected rather than waiting for the infestation to become a major problem or a nutrient deficiency to cause tree decline. Also select products that have longevity. When applying pesticides, be sure to read the label and calibrate the equipment so the correct rate, measurements, and dilution ratios are used. Mixing a slow-release fertilizer into the container or backfill soil will feed the trees what they need, when they need it, for months. Try to focus on quality to maximize the return on your investment.
Price does not have anything to do with sustainability. Higher-priced products may be more concentrated so they can be used less frequently. Or they may produce a higher quality product. An expensive product that is used once to grow the best trees is more sustainable than a poorer quality product that needs to be repeated.
The biodegradable container may be considered sustainable by some. But if it has to be shipped a long distance, is expensive to purchase, and used only once rather than being recycled, it may not be sustainable.
Consider also that chemical fertilizer is not organic but pound for pound, it has a much higher nutrient content than organic fertilizers, plus it is cheaper to ship and more readily available to the tree roots. Therefore it may be sustainable. On the other hand, slow-release fertilizers with a highly efficient technology are also sustainable.
Sustainable Trees
Not long ago, trees from around the world could be introduced into the landscape and provided with the care needed to ensure their long-term beauty and success. Pesticide use was widespread and its effectiveness unquestioned. Labor for intensive care was available and affordable, and the supply of natural resources was considered unlimited.
However, much has changed in recent decades. We have become painfully aware of the limits of our natural resources and the precarious balance of nature in which we play a pivotal role. Many in our society are looking for ways to reduce human impacts on the environment. Arborists and foresters should find that a list of sustainable trees and sustainable practices is an invaluable resource.
Tree Lists
Careful tree selection is the first step in developing a balanced and self-perpetuating landscape. However, tree survival with minimal maintenance is not the only issue in sustainability. Invasive exotic trees have escaped from managed landscapes, displaced native trees, and disrupted natural ecosystems. The use of these invasive trees cannot be seen as sustainable except in very controlled situations. For example if a site was very hostile toward trees, an invasive tree that survives might be the right choice for that site.
A key to sustainable planting is matching the tree to the conditions at the installation site. The best installation procedures will not save a tree that is poorly suited for the site. Trees vary in their ability to tolerate site conditions such as soil type, extreme heat or cold; wet or dry soils; sun or shade; and high or low pH. Plus, climatic conditions, exposure to sun and wind, subsurface soil, and moisture conditions, available space for the tree's roots as well as branches, etc. must all be considered when selecting trees for a particular location. Sustainable or not, if one ignores the site and a tree's cultural requirements, that tree will suffer. The tree also should not outgrow its allotted space and should be healthy and vigorous when installed.
Some of the best sustainable trees:
Botanical name Common Name
Abies species Fir
Acer rubrum and other small maples
Aesculus species Buckeye
Alnus incana White Alder
Amelanchier species Serviceberry
Betula nigra River Birch
Carpinus species Hornbeam
Cedrus libani Cedar of Lebanon
Cercidiphyllum japonicum Katsuratree
Cercis canadensis Redbud
Chamaecyparis species Falsecypress
Chionanthus retusus Chinese Fringetree
Cladrastis kentukea (lutea) American Yellowwood
Cornus kousa Kousa Dogwood
Corylus species Filbert
Cratageus viridis Green Hawthorn
Cryptomeria japonica Japanese Cedar
Davidia involucrata Dove-tree
Eucommia ulmoides Hardy Rubber Tree
Fagus species Beech
Franklinia alatamaha Franklin Tree
Ginkgo biloba Maidenhair Tree
Gymnocladus dioicus Kentucky Coffeetree
Halesia species Silverbell
Hammamelis species Witchhazel
Juniperus virginiana Eastern Red Cedar
Kalopanax septemlobus Castor-aralia
Koelreuteria paniculata Goldenraintree
Larix species Larch
Liquidambar styraciflua American Sweetgum
Liriodendron tulipifera Tuliptree
Maackia amurensis Amur Maackia
Magnolia species Magnolia
Malus species Crabapple
Metasequoia glyptostroboides Dawn Redwood
Nyssa sylvatica Black Tupelo
Ostrya virginiana American Hop Hornbeam
Oxydendrum arboreum Sourwood
Parrotia persica Persian Parrotia
Phellodendron amurense Amur Corktree
Picea species Spruce
Pinus species Pine
Prunus sargentii Sargent Cherry
Pseudolarix amabilis Golden-larch
Pyrus calleryana Callery Pear
Quercus species Oak
Sassafras albidum Common Sassafras
Sophora japonica Japanese Pagoda Tree
Stewartia species Stewartia
Styrax japonica Japanese Snowbell
Syringa reticulata Japanese Tree Lilac
Taxodium species Baldcypress
Thuja species Arborvitae
Tilia species Linden
Tsuga species Hemlock
Ulmus parvifolia Lacebark Elm
What does "sustainability" mean when dealing with trees? Can trees be produced with an official sustainability label on them? In the near future, we may be asking nurseries to undergo a periodic review process to maintain their claim that they are using sustainable practices. The nursery industry has always been in the business of improving the environment. Millions of trees are grown each year to beautify our surroundings, fix carbon, create oxygen, and moderate temperatures. However, some ecological impact during the growing process is unavoidable, but nurseries can minimize their impact by using management techniques, sprays, fertilizers, and equipment that are all sustainable.
There is widespread confusion about sustainability that has arborists as well as nurseries believing that sustainability is all about using "organic" products and production methods or growing native trees only. While some growers feel that inorganic fertilizer and chemical use are not sustainable, others feel that it is the process that defines sustainability. Actually, sustainability requires leaving a small environmental footprint and using the most effective products in the most efficient manner.
A sustainable urban forestry program should include goals for all elements of the sustainability system such as vehicles, buildings, employees, tree species selection, tree placement and stabilization, soil volume characteristics, design guidelines, municipal code, green-gray infrastructure interface, solar access and building envelopes, waste stream, delivery stream, pruning rotation, etc. Sustainability does not mean trees must be native. All trees regardless of their origin can be sustainable if they meet the sustainability requirements. These details include selecting species to match site-specific environmental factors. This includes consideration to mature tree size, hardiness, urban tolerances, minimal insect and disease problems, nuisance fruit, soil conditions, biological activity, water holding capacity, and soil concerns. Soil concerns deal with compaction, fertility, microbial activity, and what needs to be done to meet any shortcomings. Also look at species diversification, proper installation, root stabilizing (if warranted), and irrigation requirements. Consideration should be given to pruning, maintenance, and future replacement. Do not overlook the importance of young tree care and preservation guidelines such as impacts of root pruning for sidewalk, curb, and gutter programs.
Bare Root Tree
The Process
Efficient sustainability can be achieved by the following:
- select products that are known to work,
- be proactive toward potential problems,
- avoid using pesticides on trees that do not need treatment,
- add compost to the soil and mulch on the surface after tree installation,
- use products and stabilizers that require little labor and are very easy to use,
- use products that do not escape into the environment or beyond their intended use,
- follow recommended product directions exactly,
- recycle whenever possible,
- reduce waste.
Using products and labor efficiently is necessary as costs have risen in recent years. This may require inventive managers to discover new and efficient ways to apply products as well as effectively managing the trees growth.
For example, using root stabilizers instead of staking and guy wires, etc. saves time and money not only to purchase the product but to install it as well. Furthermore, the stabilizer does not need to ever be removed unless desired to recycle for a future installation. Metal stabilizers tend to be expensive but they are recyclable, while wood stabilizers are homemade for low cost, but never need to be removed.
Being pro-active is necessary when selecting and applying fertilizers or pesticides. For example, use a certain fertilizer or pesticide if it will save time and money in the long run. Fix insect and disease problems when first detected rather than waiting for the infestation to become a major problem or a nutrient deficiency to cause tree decline. Also select products that have longevity. When applying pesticides, be sure to read the label and calibrate the equipment so the correct rate, measurements, and dilution ratios are used. Mixing a slow-release fertilizer into the container or backfill soil will feed the trees what they need, when they need it, for months. Try to focus on quality to maximize the return on your investment.
Price does not have anything to do with sustainability. Higher-priced products may be more concentrated so they can be used less frequently. Or they may produce a higher quality product. An expensive product that is used once to grow the best trees is more sustainable than a poorer quality product that needs to be repeated.
The biodegradable container may be considered sustainable by some. But if it has to be shipped a long distance, is expensive to purchase, and used only once rather than being recycled, it may not be sustainable.
Consider also that chemical fertilizer is not organic but pound for pound, it has a much higher nutrient content than organic fertilizers, plus it is cheaper to ship and more readily available to the tree roots. Therefore it may be sustainable. On the other hand, slow-release fertilizers with a highly efficient technology are also sustainable.
Sustainable Trees
Not long ago, trees from around the world could be introduced into the landscape and provided with the care needed to ensure their long-term beauty and success. Pesticide use was widespread and its effectiveness unquestioned. Labor for intensive care was available and affordable, and the supply of natural resources was considered unlimited.
However, much has changed in recent decades. We have become painfully aware of the limits of our natural resources and the precarious balance of nature in which we play a pivotal role. Many in our society are looking for ways to reduce human impacts on the environment. Arborists and foresters should find that a list of sustainable trees and sustainable practices is an invaluable resource.
Tree Lists
Careful tree selection is the first step in developing a balanced and self-perpetuating landscape. However, tree survival with minimal maintenance is not the only issue in sustainability. Invasive exotic trees have escaped from managed landscapes, displaced native trees, and disrupted natural ecosystems. The use of these invasive trees cannot be seen as sustainable except in very controlled situations. For example if a site was very hostile toward trees, an invasive tree that survives might be the right choice for that site.
A key to sustainable planting is matching the tree to the conditions at the installation site. The best installation procedures will not save a tree that is poorly suited for the site. Trees vary in their ability to tolerate site conditions such as soil type, extreme heat or cold; wet or dry soils; sun or shade; and high or low pH. Plus, climatic conditions, exposure to sun and wind, subsurface soil, and moisture conditions, available space for the tree's roots as well as branches, etc. must all be considered when selecting trees for a particular location. Sustainable or not, if one ignores the site and a tree's cultural requirements, that tree will suffer. The tree also should not outgrow its allotted space and should be healthy and vigorous when installed.
Some of the best sustainable trees:
Botanical name Common Name
Abies species Fir
Acer rubrum and other small maples
Aesculus species Buckeye
Alnus incana White Alder
Amelanchier species Serviceberry
Betula nigra River Birch
Carpinus species Hornbeam
Cedrus libani Cedar of Lebanon
Cercidiphyllum japonicum Katsuratree
Cercis canadensis Redbud
Chamaecyparis species Falsecypress
Chionanthus retusus Chinese Fringetree
Cladrastis kentukea (lutea) American Yellowwood
Cornus kousa Kousa Dogwood
Corylus species Filbert
Cratageus viridis Green Hawthorn
Cryptomeria japonica Japanese Cedar
Davidia involucrata Dove-tree
Eucommia ulmoides Hardy Rubber Tree
Fagus species Beech
Franklinia alatamaha Franklin Tree
Ginkgo biloba Maidenhair Tree
Gymnocladus dioicus Kentucky Coffeetree
Halesia species Silverbell
Hammamelis species Witchhazel
Juniperus virginiana Eastern Red Cedar
Kalopanax septemlobus Castor-aralia
Koelreuteria paniculata Goldenraintree
Larix species Larch
Liquidambar styraciflua American Sweetgum
Liriodendron tulipifera Tuliptree
Maackia amurensis Amur Maackia
Magnolia species Magnolia
Malus species Crabapple
Metasequoia glyptostroboides Dawn Redwood
Nyssa sylvatica Black Tupelo
Ostrya virginiana American Hop Hornbeam
Oxydendrum arboreum Sourwood
Parrotia persica Persian Parrotia
Phellodendron amurense Amur Corktree
Picea species Spruce
Pinus species Pine
Prunus sargentii Sargent Cherry
Pseudolarix amabilis Golden-larch
Pyrus calleryana Callery Pear
Quercus species Oak
Sassafras albidum Common Sassafras
Sophora japonica Japanese Pagoda Tree
Stewartia species Stewartia
Styrax japonica Japanese Snowbell
Syringa reticulata Japanese Tree Lilac
Taxodium species Baldcypress
Thuja species Arborvitae
Tilia species Linden
Tsuga species Hemlock
Ulmus parvifolia Lacebark Elm
Tree Benefits Estimator
One of the greatest sustainability challenges facing public power, municipalities, and others is environmental stewardship. It is increasingly important that everyone not only take steps toward local environmental improvements, but measure the effectiveness of their efforts. The measurements are important to local communities in understanding how they can control their environmental future and the cost of doing so. It is also important for utilities to be able to measure environmental impacts that, in the future, may be reported to state and federal governments on a voluntary or mandatory basis.
The Estimator
The Tree Benefits Estimator has been developed by a utility as a web-based application to help utilities, municipalities, and others quantify and track the benefits of installing shade trees. This program estimates the amount of energy savings in kilowatt hours (KWh), capacity savings in kilowatts (KW) and carbon and carbon dioxide (CO2) sequestration in pounds (lbs) resulting from mature trees installed in urban and suburban settings. The Tree Benefits Estimator can be used by those who have no formal background in urban forestry or demand side management utility practices.
The Tree Benefit Estimator was developed by Sacramento Municipal Utility District (SMUD) and is based on the experience of the SMUD's Shade Tree program. In developing this simplified and easy-to-use method for estimating the tree installation benefits, broad assumptions have been made regarding the impact of trees on direct shading benefits, impacts of indirect or evapotranspiration effect, heating penalty in winter months, tree growth rates, and tree survival rates. As a result, this method may yield less precise results than a more tailored approach. Forestry staff from the Center for Urban Forest Research, the Pacific Southwest Research Station, the USDA Forest Service, and the University of California at Davis, have all worked on and reviewed the Tree Benefits Estimator.
How it Works
The Estimator will require the following items in order to calculate the benefit of installing trees:
Items to Consider
Here again is the link to the Tree Benefit Estimator.
One of the greatest sustainability challenges facing public power, municipalities, and others is environmental stewardship. It is increasingly important that everyone not only take steps toward local environmental improvements, but measure the effectiveness of their efforts. The measurements are important to local communities in understanding how they can control their environmental future and the cost of doing so. It is also important for utilities to be able to measure environmental impacts that, in the future, may be reported to state and federal governments on a voluntary or mandatory basis.
The Estimator
The Tree Benefits Estimator has been developed by a utility as a web-based application to help utilities, municipalities, and others quantify and track the benefits of installing shade trees. This program estimates the amount of energy savings in kilowatt hours (KWh), capacity savings in kilowatts (KW) and carbon and carbon dioxide (CO2) sequestration in pounds (lbs) resulting from mature trees installed in urban and suburban settings. The Tree Benefits Estimator can be used by those who have no formal background in urban forestry or demand side management utility practices.
The Tree Benefit Estimator was developed by Sacramento Municipal Utility District (SMUD) and is based on the experience of the SMUD's Shade Tree program. In developing this simplified and easy-to-use method for estimating the tree installation benefits, broad assumptions have been made regarding the impact of trees on direct shading benefits, impacts of indirect or evapotranspiration effect, heating penalty in winter months, tree growth rates, and tree survival rates. As a result, this method may yield less precise results than a more tailored approach. Forestry staff from the Center for Urban Forest Research, the Pacific Southwest Research Station, the USDA Forest Service, and the University of California at Davis, have all worked on and reviewed the Tree Benefits Estimator.
How it Works
The Estimator will require the following items in order to calculate the benefit of installing trees:
- the average cost of electricity in summer and winter months (cost of KWh),
- the tree species (common or botanical name),
- the age of the tree from the tree installation date or the tree diameter at the breast height (DBH),
- the number of trees installed (1 or more),
- the location in the US, which would determine the climate zone,
- the direction the tree faces (for trees installed next to buildings),
- the distance between the tree and the building that is being shaded.
Items to Consider
- The standardized climate zones in the US would allow the Tree Benefit Estimator to calculate the impact of ambient temperature and relative humidity on the summer cooling load and on the winter heating requirements using the Cooling and Heating Degree Days and Latent Enthalpy Hours data. The summer cooling load requirements and winter heating penalty are essentially a function of the cooling and heating degree days and direct shading impacts. The KWh impact of the tree evapotranspiration effect (or indirect effects) is essentially a function of the Latent Enthalpy Hours. However, regardless of whether a tree is installed for the energy saving benefits, the method will estimate carbon and CO2 sequestration values for the specified tree species. Fortunately, the Tree Benefit Estimator has all this climate information built into it. When using the Estimator, simply select the city closest to the location where the trees are being surveyed.
- The methodology is based on the "standard" nursery raised trees which are typically sold in 5-gallon containers, and which are usually 1 inch (2.5 cm) in diameter at the tree base (1 foot [30 cm] above the ground). The SMUD Shade Tree program has experienced that 5-gallon container trees will grow quickly and catch up with the larger 15-gallon container trees within a couple of years and thus the methodology applies for both the 5 and 15 gallon container trees. This methodology assumes that the typical (5 gallon) trees are "0" age when installed. The Tree Benefit Estimator will provide the estimates for the large selection of common species of deciduous, broadleaf evergreen, and conifer trees in the US.
- For the existing trees, the age of the tree from the installation date or the tree DBH information will determine the tree growth rate factor, which in turn determines the level of energy and carbon sequestration benefits for any year. For the trees installed by the utility, the age of the tree from the installation date or the tree DBH and the tree survival rate factor in that year will then determine together the program tree factor, which will in turn determine the level of energy and carbon sequestration benefits for the program trees in any year. In other words, the combination of the tree growth rate and the tree survival rate will determine the final multiplier factor that will estimate the appropriate level of the program tree benefits for any year. Given the age of the program tree from the installation date, the estimator will automatically multiply the energy, capacity and carbon sequestration benefit values of mature trees with the appropriate tree growth and survival rate factor. Additional manual calculations are not needed.
- If a tree is not listed, select a tree species from the list with similar characteristics (deciduous, conifer or broadleaf evergreen), and tree size (small tree or large tree).
- If carbon sequestration for shrubs is desired, use a small tree species (such as Japanese maple) to provide environmental benefits.
- A random sample could be calculated by randomly selecting at least 380 trees. That would provide a 15% plus or minus error. Then collect the data on an average tree and use the estimator for the sample data. That would give an average benefit per tree. The next step would be to multiply the average tree benefit with the total number of trees installed to derive total benefits.
Here again is the link to the Tree Benefit Estimator.
Dealing with Climate Change
By Dick Miller
The height of Hawaii’s Mauna Kea from the ocean floor base to the peak at 33,500 feet makes this the world’s tallest mountain from its base to the peak. (Mt. Everest reaches just the highest elevation.) This mass of former molten lava represents a model of the existence of all life on earth. Is it possible to alter the land and air that supports all life from ocean bottom to mountain top of this planet? Can the seven billion, seven hundred million plus humans (still growing) afford to enter uncharted territory as the atmospheric levels of greenhouse gases continue to rise?
Global warming is having an unquestionable impact on forest eco-systems everywhere. The climatic ramifications could be staggering for most all eco-systems on the planet and one segment of those systems is the urban forest. I am writing this as I watch the news of the wild fires burning in various parts of the world. The future of important urban forest functions includes their effect on storm water, wildlife management decisions, carbon storage, energy conservation, air quality, continuing an aesthetic sense of place and most importantly the effect that the shaded forest cover will have on the over-all health of this planet. To break it down even further, all forest systems will experience over a relatively short period of time, unknown biological thresholds not experienced in their evolutionary development.
Ecological indicators of change and shifts in species distribution are not new to forest science in the Americas. The decline of Populus tremuloides (quaking aspen), possibly due to effects of climate change in the western U.S. has made news for years. Digging through an outdated Harlow and Harrar 1969 “Textbook of Dendrology”, shows the original range map of P. tremuloides in central/southern Ohio. I can no longer locate the species in that area and native stands apparently are disappearing from northern reaches of the state as well. Also noted by Harlow and Harrar, Ilex opaca (American Holly) in the 200 years prior to the middle of the 20th century, was considered a southern tree. Soon after the beginning of the industrial revolution the species marched steadily northward. The ‘natural shift’ of this plant species toward the north could be due to the warming phenomena in combination with bird species (e.g. Northern Mockingbird), also simultaneously moving northward) that would aid in Ilex seed dissemination.
The primary reason for forest canopy decline where insect and disease are presently moving through forest stands may be directly related to warming. Simply put, insects and disease are secondary or even tertiary in response to other changes in the forest. Jim Chatfield, associate professor at The Ohio State University notes in 2012 "The bagworm moth (Thyridoptery x ephemeraeformis) has altered its range due to mild winters in Ohio. Prior to 1980, the insect was rarely able to survive north of the central regions of the state. Now the insect can survive the winters of Michigan.” How a species arrives in a new eco-region by migration or some form of un-natural shift, (e.g. hidden in a wooden shipping pallet of another continental origin), may be inconsequential relative to future survival of the organism. In addition, the native southern pine beetle in the east and native mountain pine beetle in the west are expanding their ranges laterally and to higher elevations. All forest types including the urban monocultures are on the brink of succumbing to insects and disease with primary foundations in minute changes in the overall climate.
Urban foresters and others, while not dealing with forest ecosystems that are totally natural, are no less responsible to ensure a viable forest canopy where the most important attribute (relative to the future urban heat island effect) is the production of shade. In the most simplistic terms, making an argument for more long-lived shade via good planting practices in science based suitable soil volumes should be without question. Relative to urban soils, site indexing indicating the ability of a soil to produce and sustain a tree over a given amount of time needs the urban foresters unfettered attention. One certainly should even contemplate the moral dynamics of utilizing only native plant material when a ‘mix-in’ of non-native non-invasive material would further the future of a shade produced and sustained over time. Finally, the essential elements of securing the urban forest for the future must include at the very least the following elements.
Drought and Urban Tolerant Trees
The following is a short list of native and introduced drought and urban tolerant trees for zones 5 to 7 that are often used. This list should be a start for the city arborist or landscape architect when making decisions about up-coming tree selections. (Cultivars, selections and provenance of each are not listed.)
Acer nigrum
Celtis occidentalis
Ginkgo biloba
Gleditsia triacanthos inermis
Gymnocladus dioicus
Juniperus virginiana
Ilex opaca
Maackia amurensis
Quercus falcata
Syringa reticulata,
Taxodium distichum,
Ulmus parvifolia
Dick Miller is the Urban Forester in Canal Winchester, Ohio
By Dick Miller
The height of Hawaii’s Mauna Kea from the ocean floor base to the peak at 33,500 feet makes this the world’s tallest mountain from its base to the peak. (Mt. Everest reaches just the highest elevation.) This mass of former molten lava represents a model of the existence of all life on earth. Is it possible to alter the land and air that supports all life from ocean bottom to mountain top of this planet? Can the seven billion, seven hundred million plus humans (still growing) afford to enter uncharted territory as the atmospheric levels of greenhouse gases continue to rise?
Global warming is having an unquestionable impact on forest eco-systems everywhere. The climatic ramifications could be staggering for most all eco-systems on the planet and one segment of those systems is the urban forest. I am writing this as I watch the news of the wild fires burning in various parts of the world. The future of important urban forest functions includes their effect on storm water, wildlife management decisions, carbon storage, energy conservation, air quality, continuing an aesthetic sense of place and most importantly the effect that the shaded forest cover will have on the over-all health of this planet. To break it down even further, all forest systems will experience over a relatively short period of time, unknown biological thresholds not experienced in their evolutionary development.
Ecological indicators of change and shifts in species distribution are not new to forest science in the Americas. The decline of Populus tremuloides (quaking aspen), possibly due to effects of climate change in the western U.S. has made news for years. Digging through an outdated Harlow and Harrar 1969 “Textbook of Dendrology”, shows the original range map of P. tremuloides in central/southern Ohio. I can no longer locate the species in that area and native stands apparently are disappearing from northern reaches of the state as well. Also noted by Harlow and Harrar, Ilex opaca (American Holly) in the 200 years prior to the middle of the 20th century, was considered a southern tree. Soon after the beginning of the industrial revolution the species marched steadily northward. The ‘natural shift’ of this plant species toward the north could be due to the warming phenomena in combination with bird species (e.g. Northern Mockingbird), also simultaneously moving northward) that would aid in Ilex seed dissemination.
The primary reason for forest canopy decline where insect and disease are presently moving through forest stands may be directly related to warming. Simply put, insects and disease are secondary or even tertiary in response to other changes in the forest. Jim Chatfield, associate professor at The Ohio State University notes in 2012 "The bagworm moth (Thyridoptery x ephemeraeformis) has altered its range due to mild winters in Ohio. Prior to 1980, the insect was rarely able to survive north of the central regions of the state. Now the insect can survive the winters of Michigan.” How a species arrives in a new eco-region by migration or some form of un-natural shift, (e.g. hidden in a wooden shipping pallet of another continental origin), may be inconsequential relative to future survival of the organism. In addition, the native southern pine beetle in the east and native mountain pine beetle in the west are expanding their ranges laterally and to higher elevations. All forest types including the urban monocultures are on the brink of succumbing to insects and disease with primary foundations in minute changes in the overall climate.
Urban foresters and others, while not dealing with forest ecosystems that are totally natural, are no less responsible to ensure a viable forest canopy where the most important attribute (relative to the future urban heat island effect) is the production of shade. In the most simplistic terms, making an argument for more long-lived shade via good planting practices in science based suitable soil volumes should be without question. Relative to urban soils, site indexing indicating the ability of a soil to produce and sustain a tree over a given amount of time needs the urban foresters unfettered attention. One certainly should even contemplate the moral dynamics of utilizing only native plant material when a ‘mix-in’ of non-native non-invasive material would further the future of a shade produced and sustained over time. Finally, the essential elements of securing the urban forest for the future must include at the very least the following elements.
- Decisions about soil volumes and soil consistency made to withstand the harshest future climate.
- Planting a diversity of species paying attention to provenance of those species choices.
- Monitoring when and how plants are installed to reduce initial stressors to help insure the future of those plants.
Drought and Urban Tolerant Trees
The following is a short list of native and introduced drought and urban tolerant trees for zones 5 to 7 that are often used. This list should be a start for the city arborist or landscape architect when making decisions about up-coming tree selections. (Cultivars, selections and provenance of each are not listed.)
Acer nigrum
Celtis occidentalis
Ginkgo biloba
Gleditsia triacanthos inermis
Gymnocladus dioicus
Juniperus virginiana
Ilex opaca
Maackia amurensis
Quercus falcata
Syringa reticulata,
Taxodium distichum,
Ulmus parvifolia
Dick Miller is the Urban Forester in Canal Winchester, Ohio
Urban Heat Islands
An urban heat island is a metropolitan area which is significantly warmer than its surrounding rural areas. The main cause of the urban heat island is urban development which uses materials that retain heat. Waste heat generated by energy usage is a secondary contributor.
As population centers grow they tend to modify a greater and greater area of land and have a corresponding increase in average temperature. Increases in heat within urban centers increases the length of growing seasons, and increases the occurrence of strong tornadoes. Heat islands decrease air quality by increasing the production of pollutants such as ozone, and decrease water quality as warmer waters flow into area streams, which stresses their ecosystems.
During the past 50 years, the annual average temperature at Louisville (KY) International Airport for example, has been warming up about eight-tenths of a degree every 10 years. This equates to an 8.3°F (4°C) increase during this past century. Louisville’s rate of warming has outpaced rural areas and is more than double the rate planet-wide. In response to this, Louisville has begun a major tree planting effort to double the number of trees installed every year.
The temperature difference between urban areas and the surrounding suburban or rural areas can be as much as 9° F (5° C). Experts say cities are hotter because their buildings, parking lots, freeways, and streets all absorb and retain heat. The darker the buildings, rooftops, and pavement, the more heat they can store and then release back into the community.
Lack of Trees
Too few trees also contribute to the problem, reducing shade and pulling less heat from the air to evaporate water they emit through their leaves. Researchers found that Louisville’s tree canopy covers about 27% of the county, while in other Southern cities trees can shade 40% to 50% of a community.
The heat-island effect makes it so cities never really cool off at night. Buildings trap the heat, the concrete, and the brick are re-radiating the heat that’s stored up during the day.
Killer Heat
Urban heat is also a growing public health concern. The US Centers for Disease Control and Prevention counted 8,015 heat-related deaths in the United States from 1979-2003. During this period, more people in the US died from extreme heat than from hurricanes, lightning, tornadoes, floods, and earthquakes combined.
Urban heat also makes air pollution worse. It can speed up the chemical process that forms lung-damaging ozone. The hotter a city is, the more energy is needed to cool it. That requires more coal-powered electricity, and that means more harmful emissions. Those emissions contribute to ozone and elevated levels of particulate matter. Burning more coal also pumps more carbon dioxide into the air, which scientists say has been contributing to global warming, making urban heat even more pronounced. Fortunately, in the past few years, Global Warming has become a topic of interest, especially on the nightly news broadcasts. People are becoming informed about the subject and what it is going to take to slow down the process. This interest is also predicted to create a major nursery tree shortage in the next few years.
Measuring Changes
The weather data is measured in two ways:
Cooling the City
Solutions to the problem can take many forms. Examples include:
An urban heat island is a metropolitan area which is significantly warmer than its surrounding rural areas. The main cause of the urban heat island is urban development which uses materials that retain heat. Waste heat generated by energy usage is a secondary contributor.
As population centers grow they tend to modify a greater and greater area of land and have a corresponding increase in average temperature. Increases in heat within urban centers increases the length of growing seasons, and increases the occurrence of strong tornadoes. Heat islands decrease air quality by increasing the production of pollutants such as ozone, and decrease water quality as warmer waters flow into area streams, which stresses their ecosystems.
During the past 50 years, the annual average temperature at Louisville (KY) International Airport for example, has been warming up about eight-tenths of a degree every 10 years. This equates to an 8.3°F (4°C) increase during this past century. Louisville’s rate of warming has outpaced rural areas and is more than double the rate planet-wide. In response to this, Louisville has begun a major tree planting effort to double the number of trees installed every year.
The temperature difference between urban areas and the surrounding suburban or rural areas can be as much as 9° F (5° C). Experts say cities are hotter because their buildings, parking lots, freeways, and streets all absorb and retain heat. The darker the buildings, rooftops, and pavement, the more heat they can store and then release back into the community.
Lack of Trees
Too few trees also contribute to the problem, reducing shade and pulling less heat from the air to evaporate water they emit through their leaves. Researchers found that Louisville’s tree canopy covers about 27% of the county, while in other Southern cities trees can shade 40% to 50% of a community.
The heat-island effect makes it so cities never really cool off at night. Buildings trap the heat, the concrete, and the brick are re-radiating the heat that’s stored up during the day.
Killer Heat
Urban heat is also a growing public health concern. The US Centers for Disease Control and Prevention counted 8,015 heat-related deaths in the United States from 1979-2003. During this period, more people in the US died from extreme heat than from hurricanes, lightning, tornadoes, floods, and earthquakes combined.
Urban heat also makes air pollution worse. It can speed up the chemical process that forms lung-damaging ozone. The hotter a city is, the more energy is needed to cool it. That requires more coal-powered electricity, and that means more harmful emissions. Those emissions contribute to ozone and elevated levels of particulate matter. Burning more coal also pumps more carbon dioxide into the air, which scientists say has been contributing to global warming, making urban heat even more pronounced. Fortunately, in the past few years, Global Warming has become a topic of interest, especially on the nightly news broadcasts. People are becoming informed about the subject and what it is going to take to slow down the process. This interest is also predicted to create a major nursery tree shortage in the next few years.
Measuring Changes
The weather data is measured in two ways:
- Compare the change in average annual temperatures every 10 years to changes across rural and urban areas in the United States, and the planet overall.
- Examine the growth over time by comparing temperatures in the city with nearby rural temperatures.
Cooling the City
Solutions to the problem can take many forms. Examples include:
- Advocating efforts to design and build a cooler urban area with trees.
- Building codes should include green building design incentives to encourage such things as tree-covered parking lots and lighter-colored or green roofs.
- Offer subsidies to businesses and government institutions to help pay for roofs covered with solar collectors or green plants, and parking lots that drain into gardens.
- Install solar collectors as “a roof” over parking lots. Not only will this keep cars cooler, but it will provide electricity that would provide power to recharge electric vehicles parked in the garage.
- Install as many trees and shrubs as possible throughout the city.
- Take actions to minimize development impacts on microclimates as well as human and wildlife habitats.
- Green roofs on buildings are excellent insulators during the warm weather months and the plants cool the surrounding environment. Air quality is improved as the plants absorb and convert carbon dioxide to oxygen.
- The City of New York determined that the cooling potential per area was highest for street trees, followed by living roofs, light covered surfaces, and open space planting. As a result of this study, the Mayor began a major tree planting program to install as many as one million street trees.
- Two identical office buildings in Sydney, Australia provided proof that surrounding rooftop solar panels with trees and other vegetation make them produce more power, than the same solar panels by themselves.
Lumber Salvage From Urban Trees
Every municipality is faced with the question of what to do with tree trimmings. Whether it is routine pruning of diseased or dying trees; utility trimmings; or dealing with tree damage from storms; finding a place for downed wood can be a big challenge. Finding a use for it rather than burning or dumping it at a landfill is preferred, but access to cost-effective resources for reuse varies greatly from community to community.
There are very few local mills or companies that will buy and haul away mixed municipal logs. The higher quality wood is marketable and could eventually become a useful product. Sometimes the lower end wood can become pallets, trailer beds, etc. All the remaining smaller logs and sections containing metal driven into the wood, can only be chipped or split for firewood.
Disposal of Wood and Chips
Getting rid of tree trimmings and wood debris is a major problem for municipalities and their forestry departments. Municipal parks and landscape departments most easily utilize wood chips for mulch. Chips may also be made available to residents, golf courses, and botanical gardens. Chips can be re-chipped into smaller pieces and then added to the compost pile. Chips coming from brush are generally too poor in quality for anything but composting, and they are very good for that.
Sometimes the chips can be sold as bio-fuel or as a bulking agent for a sewage treatment plant's aerobic composting operations. Agricultural communities can use wood chips as bedding for animals and poultry. Some high-quality chips can be used for making particleboard and paper products. Some communities have programs where residents can have a load of chips delivered to their driveway. The residents are encouraged to use the chips to spread around the base of their trees. This mulch protects the tree trunks from mower damage while also conserving moisture, insulating the soil from temperature extremes, and keeping weeds from competing with the tree for nutrients.
Successful Chip Programs
Stroll the many trails of the Minnesota Landscape Arboretum and you will see extensive use of wood chips as mulch and trail bedding. In this popular arboretum, use of wood debris is somewhat related to “supply and demand”. Since decomposed wood chips can become a nice loamy soil amendment material, they are sometimes hard to come by for walking trails. Road projects in the Minneapolis area and tree trimming have created an abundant supply of downed wood in the region.
In Wellesley, Massachusetts, the municipal chips are stockpiled all summer long. In winter a local chip and mulch contractor removes the freshest chips and hauls them to northern New England mills that use the wood chips for conversion to paper. The returning trucks pick up bark mulch for the company's spring garden sales. Wellesley barters a deal of getting 1 load of bark mulch for the park department gardens in exchange for removing 15 loads of wood chips all at no cost. To make the mulch go further, the park crews use the older, dark woodchips left by the contractor as a 2" – 3" layer of base mulch in new planting beds. Then the bartered bark mulch is added to the top as a new 1" topdressing over the old chips.
In Kenosha, Wisconsin, the demand for logs and chips outpaced the supply. The city began their program by giving away wood chips for free and bidding out a year's supply of logs. The wood chip program could not keep up with the demand and the city had a two to three year backlog of orders to fill. When the urban forestry program grew from one crew to several crews, the demand still outpaced the supply even though two or three times the amount of chips were being produced. The city then went to a fee program. Loads of chips were delivered at a nominal cost of about $25 per load (a load was between 10 and 15 cubic yards). In the initial one or two years of this, the supply increased over demand, which was good because chips were needed in the parks. But after two years, once again the demand began to outpace the supply despite steady or increasing production. This was due mostly because of a modest annual marketing campaign. This was a good thing because the city could justify raising the fee periodically and it allowed the crews to handle the chips only once. Crews would fill the truck, have an address to dump at, and never had to stockpile the chips. The city ran short on chips for park trees but would put down a layer of Christmas tree chips (which few people wanted) and top those off with the regular hardwood chips.
Kenosha didn't take wood chips from private tree companies because the quality could be quite poor (stringy chips) and because of the logistical problems of dealing with vendors delivering chips to City customers or to park properties. Kenosha also has the customer sign a waiver that protects the city about dropping off poor quality chips, cracking sidewalks and drives etc. They do allow a supervised tree contractor working for the city to leave the chips or logs for the property owner if the property owner requested this. The city crews would do the same because it saves time in processing the chips and logs. Kenosha doesn't charge a fee to the property owner in such instances and not many people requested this even though this information is made public.
Using Downed Wood
Disposal of wood logs has its problems. Most of the small logs (3" to 8" in diameter) can be used as firewood. Some residents may take larger pieces and split it up if it is desirable firewood and is cut into 2-foot lengths. Wood larger than 8", however, is generally not as usable, especially since most street trees are not removed until absolutely necessary and there is often a lot of rot in the trunk. Sometimes the rot has been replaced with concrete or brick. Even logs without rot might contain nails that were left in the tree many years ago. All this makes the wood useless for saw logs and undesirable for firewood. However, this wood could be chipped provided a machine is available in the municipality that can handle this larger wood. In any event there is a high cost to dispose of such logs.
Kenosha developed a program for logs similar to their wood chip program. Single load orders were taken in advance and crews dropped loads off directly from the job site. In addition, some logs were salable for the pallet market, small wood workers, wood sculptors, and small mills. A log loading truck was used to facilitate this operation from the job site to the customer. Done properly, orders can be taken and filled, crews can deliver to customers from the job site and costs of producing chips and logs can be offset by charging a modest fee. The fee helps to regulate the demand to some extent. The city found that repeat customers were more likely when a fee was charged because of the shorter backlog. People who waited two years for a load did not call back again usually because the wait was too long.
Occasionally, trees of value are removed. The municipal arborist or landscape architect should pay attention to this and salvage cedar or hickory wood chips and clear logs if they become available. The City of Toledo, for example, bags up and sells hickory wood chips to residents who add the chips to their barbecue fires. Toledo also has a small sawmill that they use to cut large logs into boards, and the lumber is sold on demand. Oak and walnut are the most popular woods in demand for lumber. Toledo also sells firewood, with the price depending on whether or not it is split. The wood and log splitter are stored near the maintenance garage so on bad weather days, a couple of climbers can spend the day splitting the wood. Certain woods such as cottonwood, boxelder, and willow are free for the taking.
Wellesley, MA has worked out an agreement with a local sawmill. The mill will haul all of the stockpiled logs away and return with 50% of the salvage as lumber to meet the DPW wood demands for a year. The wood is used by the park department for picnic tables, benches, bleachers, and docks at the beach. The carpentry shop uses the finer grades of lumber for remodeling projects at schools, town hall, and other municipal buildings. The mill keeps the other 50% for their use and sale. This covers their cost of hauling and scanning the municipal logs for metal prior to sawing.
Wood Recycling Concerns
Municipalities considering a wood recycling program have a number of issues to sort through, including: how to collect, sort, and process the wood; the potential buyers or users; what should be sold or what should be given away; and what will be the response of city government and community leaders, and how can we invest them in our efforts?
Many people express frustration about the incredible amounts of wood wasted in the U.S. Years ago, a lot of the wood was wasted because brush was piled up and burned. More wood was removed from urban areas over the past several years than harvested from our nation's forests. As the cost of energy goes up, more demand for wood is created. Some communities and individual citizens consider wood give-away stations as unsightly or they are fearful that the heat generated by decomposing wood might ignite. In some cases, wood and chip piles attract other types of dumping.
Many people would like to see easier, more efficient ways of making downed wood available for sale to small-scale markets such as carvers, artists, and craftspeople. Cost effective access could also encourage wood-related small personal businesses such as custom sawing, firewood lots, and specialized manufacturing.
Urban tree care budgets are known for their unstable nature. Strong local budgets for urban tree management are and will continue to be inconsistent. Some people see the urban tree as sacred, one that should not be touched until dead. Others feel municipal arborists should consider harvesting timber for products to support the low forestry budget. Every city forester knows that there are typically several dozen or more trees at any given time that are at risk but they do not have the resources to deal with them.
Some tree removal companies in California especially, have found the use of portable biochar ovens as a suitable way of disposing of brush, branches, and small diameter logs. The empty oven is delivered to the job site where it is filled during the cleanup. The oven is returned to the yard where it is fired up and 2 or 3 days later, biochar is available for use by their customers, city departments, or bagged up and sold to landscaping companies.
Stump Disposal
Grinding the stump where it sits in the ground is the best way to dispose of tree stumps. Stump grinding machines are available at reasonable costs and can dispose of 90% of the stumps in a municipal forestry operation. The stump grindings can be taken to a compost facility where they will decompose into a fine mulch in a couple of months. Many cities use the local leaf compost to fill the stump holes after the stump grindings have been removed.
Stumps that are dug must be buried in a land fill or a stump dump, if permits can be obtained. The only other viable solution is using a whole tree chipper to reduce the stump to chips. These high priced machines are available for purchase or rental. The disposal of vines and brush is often difficult with chippers. Disposal of this debris is better with a large machine called a tub grinder. However, most tub grinders cannot handle large wood, logs, or stumps like a whole tree chipper can.
Conclusion
The basic way of disposing of all wood products is to be creative and resourceful to finding a way that works best for your community.
Every municipality is faced with the question of what to do with tree trimmings. Whether it is routine pruning of diseased or dying trees; utility trimmings; or dealing with tree damage from storms; finding a place for downed wood can be a big challenge. Finding a use for it rather than burning or dumping it at a landfill is preferred, but access to cost-effective resources for reuse varies greatly from community to community.
There are very few local mills or companies that will buy and haul away mixed municipal logs. The higher quality wood is marketable and could eventually become a useful product. Sometimes the lower end wood can become pallets, trailer beds, etc. All the remaining smaller logs and sections containing metal driven into the wood, can only be chipped or split for firewood.
Disposal of Wood and Chips
Getting rid of tree trimmings and wood debris is a major problem for municipalities and their forestry departments. Municipal parks and landscape departments most easily utilize wood chips for mulch. Chips may also be made available to residents, golf courses, and botanical gardens. Chips can be re-chipped into smaller pieces and then added to the compost pile. Chips coming from brush are generally too poor in quality for anything but composting, and they are very good for that.
Sometimes the chips can be sold as bio-fuel or as a bulking agent for a sewage treatment plant's aerobic composting operations. Agricultural communities can use wood chips as bedding for animals and poultry. Some high-quality chips can be used for making particleboard and paper products. Some communities have programs where residents can have a load of chips delivered to their driveway. The residents are encouraged to use the chips to spread around the base of their trees. This mulch protects the tree trunks from mower damage while also conserving moisture, insulating the soil from temperature extremes, and keeping weeds from competing with the tree for nutrients.
Successful Chip Programs
Stroll the many trails of the Minnesota Landscape Arboretum and you will see extensive use of wood chips as mulch and trail bedding. In this popular arboretum, use of wood debris is somewhat related to “supply and demand”. Since decomposed wood chips can become a nice loamy soil amendment material, they are sometimes hard to come by for walking trails. Road projects in the Minneapolis area and tree trimming have created an abundant supply of downed wood in the region.
In Wellesley, Massachusetts, the municipal chips are stockpiled all summer long. In winter a local chip and mulch contractor removes the freshest chips and hauls them to northern New England mills that use the wood chips for conversion to paper. The returning trucks pick up bark mulch for the company's spring garden sales. Wellesley barters a deal of getting 1 load of bark mulch for the park department gardens in exchange for removing 15 loads of wood chips all at no cost. To make the mulch go further, the park crews use the older, dark woodchips left by the contractor as a 2" – 3" layer of base mulch in new planting beds. Then the bartered bark mulch is added to the top as a new 1" topdressing over the old chips.
In Kenosha, Wisconsin, the demand for logs and chips outpaced the supply. The city began their program by giving away wood chips for free and bidding out a year's supply of logs. The wood chip program could not keep up with the demand and the city had a two to three year backlog of orders to fill. When the urban forestry program grew from one crew to several crews, the demand still outpaced the supply even though two or three times the amount of chips were being produced. The city then went to a fee program. Loads of chips were delivered at a nominal cost of about $25 per load (a load was between 10 and 15 cubic yards). In the initial one or two years of this, the supply increased over demand, which was good because chips were needed in the parks. But after two years, once again the demand began to outpace the supply despite steady or increasing production. This was due mostly because of a modest annual marketing campaign. This was a good thing because the city could justify raising the fee periodically and it allowed the crews to handle the chips only once. Crews would fill the truck, have an address to dump at, and never had to stockpile the chips. The city ran short on chips for park trees but would put down a layer of Christmas tree chips (which few people wanted) and top those off with the regular hardwood chips.
Kenosha didn't take wood chips from private tree companies because the quality could be quite poor (stringy chips) and because of the logistical problems of dealing with vendors delivering chips to City customers or to park properties. Kenosha also has the customer sign a waiver that protects the city about dropping off poor quality chips, cracking sidewalks and drives etc. They do allow a supervised tree contractor working for the city to leave the chips or logs for the property owner if the property owner requested this. The city crews would do the same because it saves time in processing the chips and logs. Kenosha doesn't charge a fee to the property owner in such instances and not many people requested this even though this information is made public.
Using Downed Wood
Disposal of wood logs has its problems. Most of the small logs (3" to 8" in diameter) can be used as firewood. Some residents may take larger pieces and split it up if it is desirable firewood and is cut into 2-foot lengths. Wood larger than 8", however, is generally not as usable, especially since most street trees are not removed until absolutely necessary and there is often a lot of rot in the trunk. Sometimes the rot has been replaced with concrete or brick. Even logs without rot might contain nails that were left in the tree many years ago. All this makes the wood useless for saw logs and undesirable for firewood. However, this wood could be chipped provided a machine is available in the municipality that can handle this larger wood. In any event there is a high cost to dispose of such logs.
Kenosha developed a program for logs similar to their wood chip program. Single load orders were taken in advance and crews dropped loads off directly from the job site. In addition, some logs were salable for the pallet market, small wood workers, wood sculptors, and small mills. A log loading truck was used to facilitate this operation from the job site to the customer. Done properly, orders can be taken and filled, crews can deliver to customers from the job site and costs of producing chips and logs can be offset by charging a modest fee. The fee helps to regulate the demand to some extent. The city found that repeat customers were more likely when a fee was charged because of the shorter backlog. People who waited two years for a load did not call back again usually because the wait was too long.
Occasionally, trees of value are removed. The municipal arborist or landscape architect should pay attention to this and salvage cedar or hickory wood chips and clear logs if they become available. The City of Toledo, for example, bags up and sells hickory wood chips to residents who add the chips to their barbecue fires. Toledo also has a small sawmill that they use to cut large logs into boards, and the lumber is sold on demand. Oak and walnut are the most popular woods in demand for lumber. Toledo also sells firewood, with the price depending on whether or not it is split. The wood and log splitter are stored near the maintenance garage so on bad weather days, a couple of climbers can spend the day splitting the wood. Certain woods such as cottonwood, boxelder, and willow are free for the taking.
Wellesley, MA has worked out an agreement with a local sawmill. The mill will haul all of the stockpiled logs away and return with 50% of the salvage as lumber to meet the DPW wood demands for a year. The wood is used by the park department for picnic tables, benches, bleachers, and docks at the beach. The carpentry shop uses the finer grades of lumber for remodeling projects at schools, town hall, and other municipal buildings. The mill keeps the other 50% for their use and sale. This covers their cost of hauling and scanning the municipal logs for metal prior to sawing.
Wood Recycling Concerns
Municipalities considering a wood recycling program have a number of issues to sort through, including: how to collect, sort, and process the wood; the potential buyers or users; what should be sold or what should be given away; and what will be the response of city government and community leaders, and how can we invest them in our efforts?
Many people express frustration about the incredible amounts of wood wasted in the U.S. Years ago, a lot of the wood was wasted because brush was piled up and burned. More wood was removed from urban areas over the past several years than harvested from our nation's forests. As the cost of energy goes up, more demand for wood is created. Some communities and individual citizens consider wood give-away stations as unsightly or they are fearful that the heat generated by decomposing wood might ignite. In some cases, wood and chip piles attract other types of dumping.
Many people would like to see easier, more efficient ways of making downed wood available for sale to small-scale markets such as carvers, artists, and craftspeople. Cost effective access could also encourage wood-related small personal businesses such as custom sawing, firewood lots, and specialized manufacturing.
Urban tree care budgets are known for their unstable nature. Strong local budgets for urban tree management are and will continue to be inconsistent. Some people see the urban tree as sacred, one that should not be touched until dead. Others feel municipal arborists should consider harvesting timber for products to support the low forestry budget. Every city forester knows that there are typically several dozen or more trees at any given time that are at risk but they do not have the resources to deal with them.
Some tree removal companies in California especially, have found the use of portable biochar ovens as a suitable way of disposing of brush, branches, and small diameter logs. The empty oven is delivered to the job site where it is filled during the cleanup. The oven is returned to the yard where it is fired up and 2 or 3 days later, biochar is available for use by their customers, city departments, or bagged up and sold to landscaping companies.
Stump Disposal
Grinding the stump where it sits in the ground is the best way to dispose of tree stumps. Stump grinding machines are available at reasonable costs and can dispose of 90% of the stumps in a municipal forestry operation. The stump grindings can be taken to a compost facility where they will decompose into a fine mulch in a couple of months. Many cities use the local leaf compost to fill the stump holes after the stump grindings have been removed.
Stumps that are dug must be buried in a land fill or a stump dump, if permits can be obtained. The only other viable solution is using a whole tree chipper to reduce the stump to chips. These high priced machines are available for purchase or rental. The disposal of vines and brush is often difficult with chippers. Disposal of this debris is better with a large machine called a tub grinder. However, most tub grinders cannot handle large wood, logs, or stumps like a whole tree chipper can.
Conclusion
The basic way of disposing of all wood products is to be creative and resourceful to finding a way that works best for your community.
Urban Wood Utilization Plan
The number of trees removed annually from the urban forests in the US is significant. Estimates of removal (due to pests, wind storms, construction, trees at risk, etc.) range from 16 to 38 million green tons per year. These estimates are similar to the total annual harvests from America’s national forests. According to the US Forest Service there are about 141 million acres of urban forests consisting of 25.5 billion trees, every one of which will be removed sometime in the future. This converts to about 75 billion board feet of lumber a year of urban tree residues that could be recycled instead of burned, chipped, or sent to the landfill.
Although the utilization of urban trees for wood and paper products is occurring sporadically, community officials, wood-using industries, and others are devoting resources and new initiatives to convert urban “waste” wood to useful products in addition to those products mentioned in the previous Section.
Typical Products
Typical urban wood products include firewood, grade lumber, pallet boards, and railroad ties. Wood chips can be used for mulch, compost, biomass energy, paper manufacturing, and animal bedding. Lumber products include flooring, paneling, benches, tables, chairs, and other furniture. Augmenting these initiatives are a variety of books, videos, conferences, art exhibits, and partnerships that have been developed with a specific focus on urban wood use. Lumber products in several states have expanded or created new businesses based on converting urban trees to valuable products.
Wood Utilization Plan
How a community can bring all these ideas together requires the creation of a wood utilization plan. Developing a plan for a community is quite simple and may have many beneficial results for the community. Despite the common assumption that “urban” wood has no value beyond wood chips, finding a wider variety of uses for removed trees not only promotes better resource stewardship, it has the opportunity to lower wood disposal costs, create public-private partnerships that can produce high-quality, sustainable products suitable for use in community projects and green building programs.
In developing a wood utilization plan, start by looking at objectives that are most important for your community.
Consider the following:
The following measurements may be useful to consider:
Capacity Assessment
Product Development Opportunities
First and foremost, what does your community need in terms of wood products? Generally, communities can successfully reduce their wood disposal costs and save money on the cost of the wood products used for city projects by using their own dead and dying trees.
Public- Private Partnerships
Developing partnerships with private wood industries to handle processing or to purchase finished products can be quite successful, but communities should not expect to see significant profit from municipal trees due to the challenging transportation and handling costs involved.
You will want to make many decisions about what specific services you are looking for before beginning to talk with potential partners. When interviewing possible industry cooperators, be sure to collect information and clarify details on the following:
Wood Needs
Location
Payment Types
Public Response
A strong public relations strategy may be a helpful component on a wood utilization plan. Without enough information, people can quickly and wrongly make conclusions that the city is logging streets and parks to help industries and/or staff make money from public resources.
Armed with all this information, you should be able to prioritize the goals and objectives that are most important for your planning process, recognize the types of information and/or training needs that you still may have, and identify the types of services that you need from your partners.
The number of trees removed annually from the urban forests in the US is significant. Estimates of removal (due to pests, wind storms, construction, trees at risk, etc.) range from 16 to 38 million green tons per year. These estimates are similar to the total annual harvests from America’s national forests. According to the US Forest Service there are about 141 million acres of urban forests consisting of 25.5 billion trees, every one of which will be removed sometime in the future. This converts to about 75 billion board feet of lumber a year of urban tree residues that could be recycled instead of burned, chipped, or sent to the landfill.
Although the utilization of urban trees for wood and paper products is occurring sporadically, community officials, wood-using industries, and others are devoting resources and new initiatives to convert urban “waste” wood to useful products in addition to those products mentioned in the previous Section.
Typical Products
Typical urban wood products include firewood, grade lumber, pallet boards, and railroad ties. Wood chips can be used for mulch, compost, biomass energy, paper manufacturing, and animal bedding. Lumber products include flooring, paneling, benches, tables, chairs, and other furniture. Augmenting these initiatives are a variety of books, videos, conferences, art exhibits, and partnerships that have been developed with a specific focus on urban wood use. Lumber products in several states have expanded or created new businesses based on converting urban trees to valuable products.
Wood Utilization Plan
How a community can bring all these ideas together requires the creation of a wood utilization plan. Developing a plan for a community is quite simple and may have many beneficial results for the community. Despite the common assumption that “urban” wood has no value beyond wood chips, finding a wider variety of uses for removed trees not only promotes better resource stewardship, it has the opportunity to lower wood disposal costs, create public-private partnerships that can produce high-quality, sustainable products suitable for use in community projects and green building programs.
In developing a wood utilization plan, start by looking at objectives that are most important for your community.
Consider the following:
- What is your current wood disposal system?
- Do you do all wood disposal using outside contractors or in-house labor?
- What expenses does your community face with regard to wood disposal, performing chipping and grinding operations, maintaining equipment, etc.?
- Do you currently create any products from your wood residues? Are these sold or given away? Do you have a formal procedure for this?
- Does your community have any obvious wood product needs?
- How supportive is your staff and community to new urban forestry practices?
The following measurements may be useful to consider:
- Diameter – typically at least a 10” DBH is needed for a log to be millable.
- Height or length to the first branch – at least an 8’ long log is desirable for milling, but shorter logs may be considered depending on the types of products planned.
- Forest mortality and health – number of trees removed annually.
- Accessibility – felling the tree safely without cutting the log into smaller segments.
- Quality – obvious damage, scarring, metal, or other contaminants that would restrict their use.
- Species – different species can be more suitable for some products than others.
Capacity Assessment
- What role do private contractors currently play in your tree care and removal operations?
- How much staff time is available for handling, sorting, and processing the products from your trees?
- What kinds of training do the staff members currently have? Are there ways to get additional training in log evaluation, species identification, harvesting and safe felling techniques, log bucking, equipment usage, wood handling, and sorting?
- What kinds of equipment are available, especially regarding transporting and sorting logs, chipping, grinding, and other processing?
- Do you have a place available with ample space for collecting, sorting, and/or processing wood residues?
- Do you have appropriate areas to store processed lumber, firewood, mulch, or other products?
- Can you create systems to streamline picking up and transporting logs, such as coordinating the removal of millable trees around similar dates and locations?
- Are there any quarantine regulations (such as for the emerald ash borer) or other local ordinances that pose restrictions on the processing of your wood residues?
Product Development Opportunities
First and foremost, what does your community need in terms of wood products? Generally, communities can successfully reduce their wood disposal costs and save money on the cost of the wood products used for city projects by using their own dead and dying trees.
- Some of the best uses for logs are finished lumber and other products such as flooring and paneling.
- Capitalize on the talent of local woodworkers and artists, especially with dead trees of particular community or historical significance.
- Could city trees be used for memorial park benches or conference tables in city hall?
- Would students in vocational and/or construction engineering courses be able to use the wood?
- Could they be used in low-income housing programs or sold to citizens with profits coming back to a city tree fund?
- Do you have sizable logs available that could be simply rough-milled and used to meet ongoing city maintenance needs?
- Do you have needs for landscape timbers, trail walkways, boardwalks, and borders, truck sideboards, barricades, equipment storage, or other simple cut-to-order wood products that could be milled quickly and at a much lower cost than purchasing from traditional lumber yards?
- Do you have large quantities of lower-quality wood available and needs for firewood, mulch, compost, or boiler fuel? Are there outside markets for any of these products?
- Some communities have firewood, mulch, and/or compost giveaway programs that are very popular with residents.
- Other communities use their own wood chip mulch and compost in city landscaping operations.
- Some communities have been able to address their costs for both heating and wood disposal by installing a wood bio-mass boiler.
Public- Private Partnerships
Developing partnerships with private wood industries to handle processing or to purchase finished products can be quite successful, but communities should not expect to see significant profit from municipal trees due to the challenging transportation and handling costs involved.
You will want to make many decisions about what specific services you are looking for before beginning to talk with potential partners. When interviewing possible industry cooperators, be sure to collect information and clarify details on the following:
- Are they interested in single-log pickup or do they only want to be called if you have a specified quantity available?
- If you intend to receive finished wood products, what is their typical turnaround time?
- What services do they provide (chipping, grinding, milling, kiln-drying, air-drying, plaining, etc.)?
Wood Needs
- Do they have limits on the species, size, quantities, and/or condition of the wood?
- Will they accept and process all logs that you set aside?
- Will the community be expected to pre-screen or sort the material in advance or will the processor provide sorting as an additional paid service?
- Can the processor provide some simple training for municipal employees to ensure that log quality requirements are understood?
Location
- Where will processing take place?
- Is any additional transportation needed?
- Can the processing take place on city property and/or at the wood collection site?
Payment Types
- What types of payment will be considered?
- Can you retain a portion of the final lumber products with no money exchanged?
- Will there be a charge for the hours of service provided?
Public Response
A strong public relations strategy may be a helpful component on a wood utilization plan. Without enough information, people can quickly and wrongly make conclusions that the city is logging streets and parks to help industries and/or staff make money from public resources.
- Local media have been particularly responsive to stories about woodworkers, sawmills, artists, and community projects that have recovered dead ash trees in the wake of the emerald ash borer crisis.
- Others in your community can help with promoting your wood use efforts.
- You may also have good success working with park volunteers and other community services groups, student organizations, and green building enthusiasts.
- If possible, create opportunities for citizen involvement, especially by allowing woodworkers or community members to purchase or acquire lumber and other wood products.
- Use explanatory signage on high-profile wood projects to tell the story to the public.
Armed with all this information, you should be able to prioritize the goals and objectives that are most important for your planning process, recognize the types of information and/or training needs that you still may have, and identify the types of services that you need from your partners.
Planting Under a Tree
There is a right way and a wrong way to establish a garden under a tree. Being aware of a tree's root system and the tree's cultural requirements allows the creation of a garden where new plants and the tree will live together. Caution is required to avoid damaging the tree's roots. Also realize that the garden plants will need to cope with dry soil, shade, root competition, and ever-changing moisture and light conditions.
The Tree
Not all trees are created equal. Each requires specific light, soil, and moisture conditions to survive and remain healthy. Some tree species are extremely sensitive to major soil disturbance. Planting beneath trees that are sensitive to having their roots disturbed may need to have the proposed plantings scaled back or carried out over a few years.
Trees that will not tolerate root disturbance
Sugar maples (Acer saccharum)
Buckeyes (Aesculus spp.)
Dogwoods (Cornus spp.)
Beeches (Fagus spp.)
Larches (Larix spp.)
Magnolias (Magnolia spp.)
Pines (Pinus spp.)
Cherries and plums (Prunus spp.)
Scarlet oaks (Quercus coccinea)
Red oaks (Quercus rubra)
Black oak (Quercus velutina)
Lindens (Tilia spp.)
Hemlocks (Tsuga spp.)
Trees that tolerate some root disturbance
Red maples (Acer rubrum)
River birches (Betula nigra)
Hornbeam (Carpinus spp.)
Hickories (Carya spp.)
Redbuds (Cercis canadensis)
White ashes (Fraxinus americana)
Ironwood (Ostrya virginiana)
Sourwood (Oxydendrum arboreum)
Spruces (Picea spp.)
Sycamore (Platanus occidentalis)
Swamp white oak (Quercus bicolor)
Trees that tolerate root disturbance
Silver maples (Acer saccharinum)
Pecan (Carya illinoinensis)
Hawthorns (Crataegus spp.)
Ginkgos (Ginkgo biloba)
Honeylocusts (Gleditsia triacanthos)
Kentucky coffeetree (Gymnocladus dioicus)
Crabapples (Malus spp.)
Poplars (Populus spp.)
White oak (Quercus alba)
Willows (Salix spp.)
Arborvitae (Thuja spp.)
The Tree Roots
Massive undertakings to alter the grade of the landscape or to change soil pH under a tree are difficult and often impractical. Adding a layer of soil that is more than 2 inches (5 cm) deep, for example, can reduce moisture and oxygen availability, and hinder gas exchange to existing roots, causing sensitive trees to suffer and even die.
Most trees have large major roots that extend several feet into the soil to anchor them against strong winds. The majority of a tree's roots, however, are small woody roots with fine-hair roots that grow within the upper 12 to 18 inches (30-45 cm) of soil and extend far beyond the tree's drip line. These roots are responsible for absorbing water and nutrients from the soil.
A tree's root system and canopy determine how easy or difficult it will be to install a garden under a tree. It can be particularly troublesome to work among the extensive surface roots of shallow-rooted trees such as maples (Acer spp.) and elms (Ulmus spp.). The dense canopies and umbrella-like habits of trees such as conifers and large leafed trees such as Norway maples (Acer platanoides) and lindens (Tilia spp.), not only block sunlight but also deflect rainfall. Only the toughest garden plants have a chance of surviving in such conditions.
Before starting a garden, if turfgrass is growing or attempting to grow under the tree, the grass needs to be removed. Avoid stripping the grass with hand tools or equipment, which not only is backbreaking work but also damages a tree's fine roots. Try instead to smother the grass with five or six layers of wet newspaper, topped with a layer of organic mulch 1 to 2 inches (2-5 cm) deep. The downside of this method is that it may take two to three months to kill the grass and perennial weeds. Chemicals such as glyphosate (Roundup) will kill the grass faster but it's important to avoid spraying herbicides on the tree because they can be absorbed through the bark and roots. Heavy doses of broadleaf herbicides and Roundup near tree roots will also harm the tree because it is a broadleaf plant.
The Garden Planting
When purchasing plants to grow under trees, think small! Find the right plant and buy it in the smallest size available. Smaller plants require a petite planting hole that will minimize the disturbance to tree roots. More plants may have to be purchased, but it will be easier tucking them among the tree's roots.
It's best for the tree to disturb the soil only where new plants will be planted. Do not cultivate the entire proposed garden area. If a root larger than 1½ to 2 inches (4-5 cm) in diameter is encountered while digging a hole for a garden plant, move the planting hole a few inches away to avoid slicing through the root. It will be okay if small tree roots are cut when digging because they will regenerate fairly quickly. When planting, spread out the roots of the garden plants as much as possible to ensure good contact with the surrounding soil. To avoid wounding the tree bark, which is an open invitation to insect and disease problems, start planting at least 12 inches (30 cm) away from the trunk and work outward.
When all the garden plants have been installed, water the entire area to settle them and the soil. Then spread a 2 to 3 inch (5-8 cm) deep layer of composted organic mulch such as wood chips, bark mulch, compost, shredded leaves, or well-rotted manure throughout the garden area to conserve moisture and keep the weeds down. The moisture that mulch can hold against a tree's bark is conducive to rot and disease, so be sure to keep the mulch at least 2 inches (5 cm) away from the flare of the tree.
Because the little garden plants with their tiny root systems are competing with a large, established tree, thoroughly water the area after planting and continue to do so, especially during dry spells, until these plants are established. Expect some losses because the small plants will not be able to compete with the tree's roots.
Avoid fertilizing for the first year after planting because it encourages more top growth than root growth. The roots are where new plants need to spend their energy if they are going to survive. If a nutrient deficiency is suspected, get a soil test first to confirm the problem. If needed, a general, slow release, balanced fertilizer, which benefits large trees as well as the garden plantings, can be broadcast throughout the garden and watered into the soil.
Annually apply a light topdressing of composted organic matter to the mulched area in spring to maintain the 2 to 3 inch (5-8 cm) deep layer of mulch. This topdressing naturally enriches the soil by adding nutrients and enhancing aeration and moisture-holding capacity. As it decomposes, it loosens heavy clay, improves drainage, and allows the plant roots to become established. Organic matter also encourages the activity of beneficial organisms that mix and aerate the soil. By following this procedure, the tree becomes more amenable to sharing its territory, and a shade garden will begin to appear.
Plants for Dry Shade
When planting a garden under mature trees, the chances of success are improved by choosing plants that are suited to the site conditions. Keep in mind that the reduced sun and moisture levels may reduce the flowering potential of the plants.
The following is a list of plants that can grow in the reduced light and moisture available under many trees.
Shrubs
Carolina allspice (Calycanthus floridus)
Cutleaf stephanandra (Stephanandra incisa)
Ninebark (Physocarpus opulifolius)
Snowberry (Symphoricarpos albus var. laevigatus)
Winterberry (Ilex verticillata)
Perennials and Grasses
Black snakeroot (Cimicifuga racemosa)
Columbine (Aquilegia spp.)
Foamflower (Tiarella spp.)
Japanese forest grass (Hakonechloa macra)
Japanese painted fern (Athyrium niponicum var. pictum)
Lungwort (Pulmonaria spp.)
Siberian iris (Iris spp.)
There is a right way and a wrong way to establish a garden under a tree. Being aware of a tree's root system and the tree's cultural requirements allows the creation of a garden where new plants and the tree will live together. Caution is required to avoid damaging the tree's roots. Also realize that the garden plants will need to cope with dry soil, shade, root competition, and ever-changing moisture and light conditions.
The Tree
Not all trees are created equal. Each requires specific light, soil, and moisture conditions to survive and remain healthy. Some tree species are extremely sensitive to major soil disturbance. Planting beneath trees that are sensitive to having their roots disturbed may need to have the proposed plantings scaled back or carried out over a few years.
Trees that will not tolerate root disturbance
Sugar maples (Acer saccharum)
Buckeyes (Aesculus spp.)
Dogwoods (Cornus spp.)
Beeches (Fagus spp.)
Larches (Larix spp.)
Magnolias (Magnolia spp.)
Pines (Pinus spp.)
Cherries and plums (Prunus spp.)
Scarlet oaks (Quercus coccinea)
Red oaks (Quercus rubra)
Black oak (Quercus velutina)
Lindens (Tilia spp.)
Hemlocks (Tsuga spp.)
Trees that tolerate some root disturbance
Red maples (Acer rubrum)
River birches (Betula nigra)
Hornbeam (Carpinus spp.)
Hickories (Carya spp.)
Redbuds (Cercis canadensis)
White ashes (Fraxinus americana)
Ironwood (Ostrya virginiana)
Sourwood (Oxydendrum arboreum)
Spruces (Picea spp.)
Sycamore (Platanus occidentalis)
Swamp white oak (Quercus bicolor)
Trees that tolerate root disturbance
Silver maples (Acer saccharinum)
Pecan (Carya illinoinensis)
Hawthorns (Crataegus spp.)
Ginkgos (Ginkgo biloba)
Honeylocusts (Gleditsia triacanthos)
Kentucky coffeetree (Gymnocladus dioicus)
Crabapples (Malus spp.)
Poplars (Populus spp.)
White oak (Quercus alba)
Willows (Salix spp.)
Arborvitae (Thuja spp.)
The Tree Roots
Massive undertakings to alter the grade of the landscape or to change soil pH under a tree are difficult and often impractical. Adding a layer of soil that is more than 2 inches (5 cm) deep, for example, can reduce moisture and oxygen availability, and hinder gas exchange to existing roots, causing sensitive trees to suffer and even die.
Most trees have large major roots that extend several feet into the soil to anchor them against strong winds. The majority of a tree's roots, however, are small woody roots with fine-hair roots that grow within the upper 12 to 18 inches (30-45 cm) of soil and extend far beyond the tree's drip line. These roots are responsible for absorbing water and nutrients from the soil.
A tree's root system and canopy determine how easy or difficult it will be to install a garden under a tree. It can be particularly troublesome to work among the extensive surface roots of shallow-rooted trees such as maples (Acer spp.) and elms (Ulmus spp.). The dense canopies and umbrella-like habits of trees such as conifers and large leafed trees such as Norway maples (Acer platanoides) and lindens (Tilia spp.), not only block sunlight but also deflect rainfall. Only the toughest garden plants have a chance of surviving in such conditions.
Before starting a garden, if turfgrass is growing or attempting to grow under the tree, the grass needs to be removed. Avoid stripping the grass with hand tools or equipment, which not only is backbreaking work but also damages a tree's fine roots. Try instead to smother the grass with five or six layers of wet newspaper, topped with a layer of organic mulch 1 to 2 inches (2-5 cm) deep. The downside of this method is that it may take two to three months to kill the grass and perennial weeds. Chemicals such as glyphosate (Roundup) will kill the grass faster but it's important to avoid spraying herbicides on the tree because they can be absorbed through the bark and roots. Heavy doses of broadleaf herbicides and Roundup near tree roots will also harm the tree because it is a broadleaf plant.
The Garden Planting
When purchasing plants to grow under trees, think small! Find the right plant and buy it in the smallest size available. Smaller plants require a petite planting hole that will minimize the disturbance to tree roots. More plants may have to be purchased, but it will be easier tucking them among the tree's roots.
It's best for the tree to disturb the soil only where new plants will be planted. Do not cultivate the entire proposed garden area. If a root larger than 1½ to 2 inches (4-5 cm) in diameter is encountered while digging a hole for a garden plant, move the planting hole a few inches away to avoid slicing through the root. It will be okay if small tree roots are cut when digging because they will regenerate fairly quickly. When planting, spread out the roots of the garden plants as much as possible to ensure good contact with the surrounding soil. To avoid wounding the tree bark, which is an open invitation to insect and disease problems, start planting at least 12 inches (30 cm) away from the trunk and work outward.
When all the garden plants have been installed, water the entire area to settle them and the soil. Then spread a 2 to 3 inch (5-8 cm) deep layer of composted organic mulch such as wood chips, bark mulch, compost, shredded leaves, or well-rotted manure throughout the garden area to conserve moisture and keep the weeds down. The moisture that mulch can hold against a tree's bark is conducive to rot and disease, so be sure to keep the mulch at least 2 inches (5 cm) away from the flare of the tree.
Because the little garden plants with their tiny root systems are competing with a large, established tree, thoroughly water the area after planting and continue to do so, especially during dry spells, until these plants are established. Expect some losses because the small plants will not be able to compete with the tree's roots.
Avoid fertilizing for the first year after planting because it encourages more top growth than root growth. The roots are where new plants need to spend their energy if they are going to survive. If a nutrient deficiency is suspected, get a soil test first to confirm the problem. If needed, a general, slow release, balanced fertilizer, which benefits large trees as well as the garden plantings, can be broadcast throughout the garden and watered into the soil.
Annually apply a light topdressing of composted organic matter to the mulched area in spring to maintain the 2 to 3 inch (5-8 cm) deep layer of mulch. This topdressing naturally enriches the soil by adding nutrients and enhancing aeration and moisture-holding capacity. As it decomposes, it loosens heavy clay, improves drainage, and allows the plant roots to become established. Organic matter also encourages the activity of beneficial organisms that mix and aerate the soil. By following this procedure, the tree becomes more amenable to sharing its territory, and a shade garden will begin to appear.
Plants for Dry Shade
When planting a garden under mature trees, the chances of success are improved by choosing plants that are suited to the site conditions. Keep in mind that the reduced sun and moisture levels may reduce the flowering potential of the plants.
The following is a list of plants that can grow in the reduced light and moisture available under many trees.
Shrubs
Carolina allspice (Calycanthus floridus)
Cutleaf stephanandra (Stephanandra incisa)
Ninebark (Physocarpus opulifolius)
Snowberry (Symphoricarpos albus var. laevigatus)
Winterberry (Ilex verticillata)
Perennials and Grasses
Black snakeroot (Cimicifuga racemosa)
Columbine (Aquilegia spp.)
Foamflower (Tiarella spp.)
Japanese forest grass (Hakonechloa macra)
Japanese painted fern (Athyrium niponicum var. pictum)
Lungwort (Pulmonaria spp.)
Siberian iris (Iris spp.)
Using Plants as Sound Barriers
Plants are often promoted for use to reduce or attenuate noise from nearby highways, industries, or other sources. Plants have the ability to absorb and scatter sound waves; they also can mask sound with the movement of their leaves. The mix of plants is important because different types of leaves reduce different types of noises. How much noise control they provide depends on the intensity, frequency and direction of the sound, and the location, height, width and density of the planting. However, the effectiveness of trees, shrubs, and ground-covers as noise reducers is still subject to some debate.
Plant Specifications
A great deal of research has been conducted over the years investigating the use of plants for street and highway noise reduction. When using plants for noise reduction, the word "thick" refers to depth of the buffer between the sound generator and a person's ears. "Length" refers to a row of plants ending at an imaginary line between the noise generator and each end of the person's property or extent of the noise. In general, the following criteria should be considered when proposing trees and other plants for sound reduction:
When plants are used as a sound barrier, sufficient growth time must be allowed for the plants to attain their optimal height and density. Since most plants are planted in smaller sizes for ease of installation and reduced plant material costs, creating an effective plant screen can take many years before the plants grow dense enough to provide the desired physical barrier. In this situation, it may be practical to build a “temporary” wood sound barrier. By the time the wood rots and the barrier falls, the trees have become effective.
Noise Barriers
Soil Berm
The best way to reduce noise with plants is to establish a soil berm for the plantings:
Barrier Walls
Since highway right-of-way widths are generally very narrow, there is usually limited space available to plant wide buffer areas of dense trees and shrubs along the highway. The intent is to reduce the noise impact on adjacent property owners. Solid noise barrier walls are now being installed along many portions of highways where abutting residential communities have complaints about traffic noise.
The addition of plants and trees can provide aesthetic visual enhancements to psychologically reduce the scale of the wall by breaking up the expanse of the wall surface and the hard edges of the ends and caps. Plantings on each side of a sound wall with taller growing trees that will over-top the height of the wall can visually reduce the apparent wall height. Shrubs planted in front of the wall and vines growing on the wall surface and over the wall top can effectively break up the surface expanse of the wall and also break up the sound waves somewhat.
Good Sound Barrier Plants
Regardless of the plants selected, they must be thick, and not necessarily tall. As with any planting effort, the selected plants must be hardy to the area; able to adapt and grow in the environmental factors of the site such as soil type, moisture availability, wind conditions, winter road salt spray, drought tolerance, full sun exposure, no maintenance after the installation contract has ended, and planted at a safe distance away from the roadway.
Plants are often promoted for use to reduce or attenuate noise from nearby highways, industries, or other sources. Plants have the ability to absorb and scatter sound waves; they also can mask sound with the movement of their leaves. The mix of plants is important because different types of leaves reduce different types of noises. How much noise control they provide depends on the intensity, frequency and direction of the sound, and the location, height, width and density of the planting. However, the effectiveness of trees, shrubs, and ground-covers as noise reducers is still subject to some debate.
Plant Specifications
A great deal of research has been conducted over the years investigating the use of plants for street and highway noise reduction. When using plants for noise reduction, the word "thick" refers to depth of the buffer between the sound generator and a person's ears. "Length" refers to a row of plants ending at an imaginary line between the noise generator and each end of the person's property or extent of the noise. In general, the following criteria should be considered when proposing trees and other plants for sound reduction:
- Tall and dense plantings in buffer strips (multiple layers) that are thick enough to be visually opaque will provide noise attenuation in the range of 3 – 10 decibels per 100 feet (30 m) of buffer thickness. The buffer strips should have mixed broadleaf plantings at least 25 feet (8 m) thick and conifers 50 to 100 feet (15-30 m) thick to be effective.
- Deciduous plants do not provide a year-round visual barrier or protection from noise. The loss of leaves in winter changes the whole character of the plant for any noise attenuation.
- Evergreens are more effective for year-round screening and noise reduction; however, if planted in close proximity to a highway or street, in a part of the country where road salt or salt compounds are used for snow and ice control, care should be given to plant selection. Choose evergreens that are salt and salt-spray tolerant such as White Fir (Abies concolor); White Spruce (Picea glauca); Colorado Spruce (Picea pungens); Austrian Pine (Pinus nigra); and Japanese Black Pine (Pinus thungergiana).
- Shrubs should be planted in front of the trees to help provide the desired density of growth close to the ground.
- Plants need to be planted as close together as practical in order to form a continuous dense barrier.
- Varying growth rates from one plant to another and from one species to another can create situations where the plants may not grow together to produce a dense barrier.
- Plants need to be planted as close to the noise source as possible rather than being planted close to the noise receptor area. The U.S. Department of Transportation has recognized that the principal effect of planting for noise reduction is psychological in nature. By removing the noise source from view, the noise awareness or annoyance can be reduced in the mind of the viewer or listener.
When plants are used as a sound barrier, sufficient growth time must be allowed for the plants to attain their optimal height and density. Since most plants are planted in smaller sizes for ease of installation and reduced plant material costs, creating an effective plant screen can take many years before the plants grow dense enough to provide the desired physical barrier. In this situation, it may be practical to build a “temporary” wood sound barrier. By the time the wood rots and the barrier falls, the trees have become effective.
Noise Barriers
- To be effective, any noise barrier must be solid since sound waves will reflect and be redirected from a solid surface.
- Sound waves can bend around and over barriers, but with less intensity.
- Trees will have a minimal effectiveness on the sound waves due to their general open trunk, branches, and varying leaf structures.
- Many barriers use a combination of plants and solid barriers, or solid barriers alone.
- In certain situations, water features can be used to mask the street sounds, but not eliminate them.
Soil Berm
The best way to reduce noise with plants is to establish a soil berm for the plantings:
- Large mounds of soil, thickly planted, as described above do a much better job of blocking sound than plants alone.
- The berm should be at least eight feet tall and 20 feet wide (2 x 6 meters), and as long as possible. A solid, well-planted berm can cut automobile and truck noise by 70% to 80% and substantially reduce sounds from playgrounds, sporting activities, or factories
Barrier Walls
Since highway right-of-way widths are generally very narrow, there is usually limited space available to plant wide buffer areas of dense trees and shrubs along the highway. The intent is to reduce the noise impact on adjacent property owners. Solid noise barrier walls are now being installed along many portions of highways where abutting residential communities have complaints about traffic noise.
The addition of plants and trees can provide aesthetic visual enhancements to psychologically reduce the scale of the wall by breaking up the expanse of the wall surface and the hard edges of the ends and caps. Plantings on each side of a sound wall with taller growing trees that will over-top the height of the wall can visually reduce the apparent wall height. Shrubs planted in front of the wall and vines growing on the wall surface and over the wall top can effectively break up the surface expanse of the wall and also break up the sound waves somewhat.
Good Sound Barrier Plants
- Bamboo is one of the best sound barrier plants to grow. In USDA Hardiness Zone 8 or higher, plant one of the Bambusa multiplex varieties, with a range from 3 to 25+ feet in height. In colder zones, Bamboo will sometimes lose some leaves during the winter. Bamboo, once topped, will remain at that height for the duration of its life. Bamboos are clumpers, meaning that they are not invasive and will not take over the landscape. Although Bamboo is technically a grass, it can be considered a tree in this application.
- Other good sound barrier plants include: abelias, junipers, and antique, wild, and species roses.
- Barberry and even some particularly thorny cacti are commonly used as barriers. Plus, dense hedges of pyracantha and its thorns will keep out all but the most determined intruder.
- Consider planting tall-growing shrubs with dense foliage such as Nandina, Callstemon, Buxus, Ligustum, Photinia, or Escallonia. These hardy shrubs will muffle the offending noise while beautifying the landscape at the same time.
- Thickets of native sassafras and pawpaw have been found to be relatively effective sound barriers.
- Also install a mix of evergreens such as arborvitaes, spruces, pines, and hollies. To be effective sound barriers, these trees must have foliage that reaches to the ground. For low sound coverage, consider yews and rhododendron.
Regardless of the plants selected, they must be thick, and not necessarily tall. As with any planting effort, the selected plants must be hardy to the area; able to adapt and grow in the environmental factors of the site such as soil type, moisture availability, wind conditions, winter road salt spray, drought tolerance, full sun exposure, no maintenance after the installation contract has ended, and planted at a safe distance away from the roadway.
Building Parklets
Parklets are the latest idea in urban planning and are becoming a trend in cities across the United States. They consist of converting 1 – 3 parking spaces along the edge of a city street, into very small parks. While a parking space is used by one or two people an hour, a parklet is being enjoyed by dozens of people an hour, all day long. They are funded by nearby businesses, but are open to everyone. In places where they have been built, they have become extremely popular and a major boost to abutting businesses.
History
Funding Sources
In almost all cases, business owners pay for the construction and maintenance of the parklets. They will vary in cost but the average is between US$15,000 and $20,000. In some cases the cities will offer design assistance or some funding. Other cities will donate the street tree that is a key feature in all parklets. Businesses are doing this as a way to beautify their city block and help attract more foot traffic. Cities see it as a low investment in innovative new public spaces.
Design Elements
Conclusion
What works in one city may not work in another. For example, parklets on the West Coast are open year-round, while those in Chicago, Boston, and Philadelphia will be closed for the winter. Cities are encouraged to experiment with what works and what does not.
Parklets are the latest idea in urban planning and are becoming a trend in cities across the United States. They consist of converting 1 – 3 parking spaces along the edge of a city street, into very small parks. While a parking space is used by one or two people an hour, a parklet is being enjoyed by dozens of people an hour, all day long. They are funded by nearby businesses, but are open to everyone. In places where they have been built, they have become extremely popular and a major boost to abutting businesses.
History
- In 2005, San Francisco converted a parking space to a park with sod, benches, and trees on a temporary basis. The abutting store had to feed the meter and replace the park features annually. This was followed in 2009, when New York City began converting several street spaces into pedestrian-only plazas.
- In 2010, San Francisco recognized the original parklet's significance and removed the meter. They also established the first permanent parklet. They currently have 38 parklets functioning with a few more in the planning stage.
- Current projects are opening in Oakland and Long Beach, CA. Long Beach is planning to create 'Bio-soil” parklets intended to help capture and divert rainwater.
- Philadelphia opened its first parklet in 2011 and is adding several more in the next few years.
- Chicago, IL, Los Angeles, CA, Boston, MA, and Roanoke, VA are also developing parklets.
Funding Sources
In almost all cases, business owners pay for the construction and maintenance of the parklets. They will vary in cost but the average is between US$15,000 and $20,000. In some cases the cities will offer design assistance or some funding. Other cities will donate the street tree that is a key feature in all parklets. Businesses are doing this as a way to beautify their city block and help attract more foot traffic. Cities see it as a low investment in innovative new public spaces.
Design Elements
- Parklets work best in front of a business that offers food or entertainment and needs walk-up customers.
- They need to be on streets with low speed limits.
- They must not be placed on corners.
- They should be visually distinctive.
- Trees are encouraged in all parklets because they can be given extra soil space under the entire parklet for proper root growth.
- The benches and chairs in one parklet must look different from any seating at the adjacent business and other parklets to reinforce the idea that these are public spaces rather than an extension of a private cafe.
- Benches in the parklet must be built-in rather than movable chairs and tables.
- Cafes are not allowed to serve customers sitting in the parklets, but the customer can carry their purchase to the parklet.
- Each parklet should average 320 square feet (30 sm) in size.
- The design should be simple and inexpensive.
- The parklets can be issued an annual permit so if it doesn't work or problems develop, it can be removed.
Conclusion
What works in one city may not work in another. For example, parklets on the West Coast are open year-round, while those in Chicago, Boston, and Philadelphia will be closed for the winter. Cities are encouraged to experiment with what works and what does not.
Preventing Invasive Plants
Arborists and landscape managers should be aware of the invasive plant problem and know what to expect. Invasive plants affect everyone. When settlers began gardening, they had a constant struggle to keep the natural ecosystem from invading and overwhelming their small cultivated patches. Today, we have so altered the landscape that the reverse is true. Many of the plants we’ve cultivated have escaped and are now threatening to invade more favorable native plants in conservation and wild areas. Also today, the U.S. Geological Survey reports that some $20 billion in environmental damage can be linked to invasive trees, plants, and wildlife. This affects not only those making a living from the land, but people everywhere.
Researchers believe there are several factors that contribute to a plant becoming invasive. Invasive plants must have:
Invasive plants are opportunistic plants that take advantage of areas with disturbed soil. They spread rapidly and crowd out desirable native species. They also compete with native species for water, nutrients, sunlight, and space. As a result, invasive species can:
Categories of Invasive Plants
Invasive Prevention
The best defense against invasive plant takeovers is constant surveillance of landscaped and natural areas and continued annual follow-up treatments of all infested sites until the problem is controlled. Early detection and treatments will minimize the costs and efforts that must be dedicated to eliminate invasive plant infestations. The longer the plants are left to establish the more rapidly they spread; the more difficult they are to control; and the more time that is needed for follow-up treatments.
Invasive Plant Control Plan
Early invasive detection and treatment along with an effective control program are the main components of a complete prevention plan. There are a few effective biological agents for invasive plant control, but they are only useful where containment is the objective. For control of heavy plant infestations, herbicides are most often used in combination with other types of control such as mechanical and cultural methods, hand pulling, mowing or cutting, and burning. Mechanical methods may disturb a site and encourage the invasive plants instead of eliminating them.
Therefore, herbicides are preferred because they are the least disruptive and the most effective and economical means for invasive plant control. They are often applied as a direct control application method for single and small infestations. Without the use of herbicides, native plants would be the losers and invasive plants would take over.
An effective control plan must begin with training for plant identification, education on the harm caused by invasive plants in the environment, herbicides and their uses, application techniques, and application timing. All landscape area managers must be able to identify invasive plants so they can be spotted for early control. Adjacent landowners should also be able to identify the plants and be encouraged to report them. Extra employee training cannot be overemphasized whether vegetation management specialists, university experts, county agents, or consultants provide it.
List of Invasive Trees, Shrubs, and Vines
The following list was prepared for Central Illinois and may need to be adapted to your area:
Amur Maple Acer ginnala
Boxelder Acer negundo
Norway Maple Acer platanoides
Porcelain Vine Ampelopsis brevipedunculata
Japanese Barberry Berberis thunbergii
Oriental Bittersweet Celastrus orbiculatus
Autumn-olive Elaeagnus umbellata
Burning Bush Euonymus alatus
European Privet Ligustrum vulgare
Japanese Honeysuckle Lonicera japonica
Amur Honeysuckle Lonicera maackii
White Mulberry Morus alba
Amur Corktree Phellodendron amurense
Common Buckthorn Rhamnus cathartica
Glossy Buckthorn Rhamnus frangula
Black Locust Robinia pseudoacacia
Multiflora Rose Rosa multiflora
Poison Ivy Toxicodendron radicans
Siberian Elm Ulmus pumila
European Cranberry-bush Viburnum opulus
Conclusion
The majority of exotic plants are not problematic and poses no threat to our natural areas. Exotic plants play an important role in modern day landscapes offering tough, resilient, and aesthetically pleasing additions to yards, streets, and urban landscapes. Prevention of invasives is obviously a moot point in many areas. While herbicides are one of the most effective and economical ways to control invasives and reclaim areas, think what the outcome would be if herbicides were not used at all.
Sources
The test that follows contains 80 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award 4.0 CEUs* for a passing grade. SAF members will earn 1.0 Cat. 1-CT credit for a passing grade. The cost for taking this test is $20 per credit. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 4.0 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, or (2) BCMA science credits and (2) BCMA practice 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.
Arborists and landscape managers should be aware of the invasive plant problem and know what to expect. Invasive plants affect everyone. When settlers began gardening, they had a constant struggle to keep the natural ecosystem from invading and overwhelming their small cultivated patches. Today, we have so altered the landscape that the reverse is true. Many of the plants we’ve cultivated have escaped and are now threatening to invade more favorable native plants in conservation and wild areas. Also today, the U.S. Geological Survey reports that some $20 billion in environmental damage can be linked to invasive trees, plants, and wildlife. This affects not only those making a living from the land, but people everywhere.
Researchers believe there are several factors that contribute to a plant becoming invasive. Invasive plants must have:
- a fast growth rate,
- seeds that germinate quickly and in high percentages,
- prolific seed production, which begins within the first few years of the invasive plant’s life,
- easy seed dispersal by animals, water, and wind,
- the ability to reproduce by seed as well as vegetatively, through suckering,
- longer flowering and fruiting periods,
- an adaptability to a wide range of soil and growing conditions.
Invasive plants are opportunistic plants that take advantage of areas with disturbed soil. They spread rapidly and crowd out desirable native species. They also compete with native species for water, nutrients, sunlight, and space. As a result, invasive species can:
- displace native species,
- reduce plant diversity and create monocultures,
- alter ecosystem processes,
- hybridize with native plants, changing their genetic makeup,
- destroy and degrade the wildlife habitats that support native animals, insects, and micro-organisms,
- create ecosystems that support aggressive, non-native plants, animals, and pathogens.
Categories of Invasive Plants
- Exotics — These are primarily European or Asian species that have been accidentally or intentionally introduced to the United States for their ornamental value or their ability to provide shade, windbreaks, and erosion control, but have escaped and now threaten native species.
- Trans-locators — These are native species that have moved out of their original range into an area that favors their over-production.
- Opportunists — These are native colonizing species that previously may have been held in check by natural processes.
Invasive Prevention
The best defense against invasive plant takeovers is constant surveillance of landscaped and natural areas and continued annual follow-up treatments of all infested sites until the problem is controlled. Early detection and treatments will minimize the costs and efforts that must be dedicated to eliminate invasive plant infestations. The longer the plants are left to establish the more rapidly they spread; the more difficult they are to control; and the more time that is needed for follow-up treatments.
Invasive Plant Control Plan
Early invasive detection and treatment along with an effective control program are the main components of a complete prevention plan. There are a few effective biological agents for invasive plant control, but they are only useful where containment is the objective. For control of heavy plant infestations, herbicides are most often used in combination with other types of control such as mechanical and cultural methods, hand pulling, mowing or cutting, and burning. Mechanical methods may disturb a site and encourage the invasive plants instead of eliminating them.
Therefore, herbicides are preferred because they are the least disruptive and the most effective and economical means for invasive plant control. They are often applied as a direct control application method for single and small infestations. Without the use of herbicides, native plants would be the losers and invasive plants would take over.
An effective control plan must begin with training for plant identification, education on the harm caused by invasive plants in the environment, herbicides and their uses, application techniques, and application timing. All landscape area managers must be able to identify invasive plants so they can be spotted for early control. Adjacent landowners should also be able to identify the plants and be encouraged to report them. Extra employee training cannot be overemphasized whether vegetation management specialists, university experts, county agents, or consultants provide it.
List of Invasive Trees, Shrubs, and Vines
The following list was prepared for Central Illinois and may need to be adapted to your area:
Amur Maple Acer ginnala
Boxelder Acer negundo
Norway Maple Acer platanoides
Porcelain Vine Ampelopsis brevipedunculata
Japanese Barberry Berberis thunbergii
Oriental Bittersweet Celastrus orbiculatus
Autumn-olive Elaeagnus umbellata
Burning Bush Euonymus alatus
European Privet Ligustrum vulgare
Japanese Honeysuckle Lonicera japonica
Amur Honeysuckle Lonicera maackii
White Mulberry Morus alba
Amur Corktree Phellodendron amurense
Common Buckthorn Rhamnus cathartica
Glossy Buckthorn Rhamnus frangula
Black Locust Robinia pseudoacacia
Multiflora Rose Rosa multiflora
Poison Ivy Toxicodendron radicans
Siberian Elm Ulmus pumila
European Cranberry-bush Viburnum opulus
Conclusion
The majority of exotic plants are not problematic and poses no threat to our natural areas. Exotic plants play an important role in modern day landscapes offering tough, resilient, and aesthetically pleasing additions to yards, streets, and urban landscapes. Prevention of invasives is obviously a moot point in many areas. While herbicides are one of the most effective and economical ways to control invasives and reclaim areas, think what the outcome would be if herbicides were not used at all.
Sources
- Discussion on LinkedIn's Urban Forestry Discussion Group, January, 2011.
- Bratkovich, Dr. Steve, “Urban Wood Utilization and Industrial Clusters: A Twin Cities Case Study”, Dovetail Partners, Inc. 2010.
- Bruggers, James, “Urban group wants to help cool down Louisville's heat island”, The Louisville Courier-Journal, May 6, 2012.
- Butler, Rhett A., “Forests Worldwide Near Tipping Point”, Mongabay.com Nov. 23, 2012.
- Chatfield, James “Plant Lovers Almanac”, Ohio State University Extension, 2012.
- “Community Urban Wood Utilization Planning Worksheet”, Southeast Michigan Resource Conservation and Development Council, 2009. Forest Ecology and Management 254: 390 – 406.
- Harlow and Harrar, “Textbook of Dendrology”, Fifth Edition 1969.
- Haworth, Kim, “In My Garden: Working Plants”, Regional Reports, January 1, 2009.
- “Invasive Plants: Weeds of the Global Garden”, Brooklyn Botanic Garden 2009.
- “Invasive Trees, Shrubs, and Vines”, Morton Arboretum, 2012.
- Lerner, Joel M., “A Good Wall, Even if It's Made of Plants, Can Reduce Highway Noise”, Washington Post, March 12, 2005.
- Lorenz, Ralph W. Lecture, Univ. Illinois, 1971.
- Patton, Zach, “On-Street Parking”, Governing Magazine. June 2012.
- Petersen, Lynette, "3 E's of Sustainability", Nursery Management & Production, November 2008.
- Taylor, Doris, “Planting under a Tree", Fine Gardening, Issue105, 2009.
- “Turning Urban and Community Trees into Products Involves the Entire Wood Use Chain”, Illinois Urban Wood Organization, 2012.
- “Urban Heat Islands”, Wikipedia, the free encyclopedia, May 2012.
- University of Rhode Island Landscape Horticulture Program, "Sustainable Trees & Shrubs", Green Shares Fact Sheet, 2008.
- Whaley, John T., “A Brief Look at Using Plants as a Sound Barrier”, Urban Forestry News, Pennsylvania Community Forests Newsletter, Vol. 15, No. 3, Summer 2007.
- Williamson, Max, "Invasive Q&A", Right of Way Vistas, Dow AgroSciences, Vol. 18. 1, 2005.
- “Wisconsin Manual of Control Recommendations for Ecologically Invasive Plants”, Bureau of Endangered Resources, Wisconsin Department of Natural Resources, 2012.
The test that follows contains 80 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award 4.0 CEUs* for a passing grade. SAF members will earn 1.0 Cat. 1-CT credit for a passing grade. The cost for taking this test is $20 per credit. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 4.0 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, or (2) BCMA science credits and (2) BCMA practice 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.