LA Course #GCE-1-1407
MULCHES, SOLAR TECHNOLOGY & NURSERY STANDARDS
Edited by Len Phillips and Richard W Gibney RLA/ISA
Sections Go directly to section by clicking on title below
MULCHES, SOLAR TECHNOLOGY & NURSERY STANDARDS
Edited by Len Phillips and Richard W Gibney RLA/ISA
Sections Go directly to section by clicking on title below
These articles discuss new trends/technology and the recently updated AAN standards that all landscape architects should be aware of to stay current in the profession.
Note: Click on green text in each section for more information.
Six Mulches for City Trees
Compaction and topsoil removal associated with site development in the city have left many soils unsuitable for growing urban trees. Consequently, soil organic matter has become much more important for growing trees in urban landscapes. What follows is a comparison of six commonly used soil mulches for growing trees in the small pits set aside in city sidewalks.
What are “Biosolid Mulches”?
Biosolids are the nutrient-rich organic materials from the treatment of sewage sludge. Biosolids have been used in reclamation of agricultural, forest, and disturbed lands since the 1960s. Studies have found the use of this material promotes increased soil fertility, improved physical properties of the soil, increased tree and forest growth, and increased microbial activity.
Some concerns associated with applying biosolids to soils include, but are not limited to, salinity, heavy metals, organic contaminants, and pathogens, as well as a poor public perception. Consequently, the US EPA requires that wastewater solids be stabilized to minimize odor generation, destroy pathogens, and reduce vector attraction. In addition, the EPA sets the ceiling and pollutant concentration levels for nutrients and metals in biosolids.
Do Biosolid Mulches Work?
The greatest increases in tree growth among the six mulches in this comparison were observed with biosolid treatments. Compared to the other five options, the total tree biomass, leaf biomass, stem biomass, and coarse root biomass were all in the best category. In addition, total organic carbon was greatest with biosolids. In most soils, nitrogen mineralization and microbial respiration was greatest with biosolids along with broad positive impacts on soil’s physical, chemical, and biological properties.
No standards currently exist for biosolid applications to urban trees, but biosolids should be applied as top-dressings or mulches at moderate rates. As a starting point, application rates for these products could be computed based on matching the nitrogen content of the material with the tree’s nitrogen demand.
Biosolids are attractive given the many potential environmental benefits. They are generated from waste products, and land applications would divert materials that may otherwise end up in landfills. More research is required regarding the persistence and toxicity of potential contaminants before implementing a biosolids program for urban trees.
What are “Biochar Mulches”?
While charcoal is used as a fuel, biochar is used as a soil amendment and was inspired by high fertility and high organic carbon contents found in anthropic soils in the Amazon Basin, referred to as Terra Preta de Indio. Today, biochar is most commonly produced through pyrolysis, which is the burning of woody biomass at 350°C to 800°C under the partial exclusion of oxygen. Biochar is generated from waste wood products and land clearing operations that divert wood materials from ending up in landfills. With products such as woody biomass, pyrolysis creates a material that is highly aromatic with carbon concentrations of 70 – 80% and it has unique properties for nutrient adsorption and stability.
Do Biochar Mulches Work?
A growing body of research is finding biochar to increase soil quality and plant growth. Biochar is also found to increase water and nutrient retention, along with increased microbial biomass and activity. In the comparison study, the total amount of organic carbon was greatest with biochar compared to the other five amendments and soil types. High amounts of tree growth, and tree biomass were found with biochar. Biochar has the additional potential benefit of carbon sequestration in the soil. No standards currently exist for biochar application to urban trees, but recent research suggests biochar can be applied annually as a top-dressing or mulch at moderate rates.
Nitrogen immobilization is a commonly raised concern with biochar. It should be noted that biochar is relatively recalcitrant, and thus the total carbon and nitrogen content may not accurately reflect what is actually available for microbial metabolism. Studies often report decreases in nutrient leaching with additions of biochar due to its high adsorption capacity. Potential negative impacts of biochar on soil quality include increasing soil pH in alkaline soils.
Urban forestry operations might be well suited for the addition of mobile, fast-pyrolysis equipment that converts urban wood waste into a bio-oil, syngas, or biochar. This equipment could be located near a biomass removal operation to convert low-value urban wood waste into easily stored and transportable fuel to be used for heat, power, and soil amendment purposes. The idea would be to generate biochar instead of creating wood chips.
What are “Compost Mulches”?
Many studies have demonstrated the value of compost applied as mulch to urban landscapes for improving soil quality and tree growth related to nutrient retention, soil organic matter quality, and microbial activity.
Do compost mulches work?
Studies are mixed about whether or not there is an increased tree growth with surface applications of compost. Most of these experiments were field based in nurseries, with larger-sized trees, and were of a long duration. In addition, these studies examined tree growth responses to compost in higher-quality soils, not in degraded soils typical of urban soil conditions. However, compost does increase the total organic carbon in all soils.
Compost should be applied annually as top dressings to the soil and at rates that are considered the current best practices for soil application.
What is “Nitrogen/Potassium Fertilizer”?
Nutrient leaching losses are a concern with both inorganic and organic fertilizers. Inorganic fertilizer salts are soluble, thus nutrients are immediately available for uptake by trees, and also thought to be more prone to leaching losses. However, nutrients may be released from organic materials at times when plant uptake is low. Tree growth is known to be limited by the nitrogen supply, especially on poorly developed soils with low fertility.
Do Nitrogen/Potassium Fertilizers Work?
Researchers found some increases in tree biomass were observed with the nitrogen/potassium fertilizer relative to the control of no treatments. This finding was expected given that inorganic fertilizers have long been used to supply nutrients for urban landscape trees. Reviews of shade tree fertilization studies, summarize the general consensus of increased tree growth with fertilization and are in agreement with other findings of increase in tree growth with the nitrogen/potassium fertilizer.
The nitrogen/potassium fertilizer (30–0–12) should be diluted with water and applied twice annually. The fertilizer applied in these treatments should be within the range of specifications for nitrogen fertilizer demands required by urban trees.
What are “Wood Chip” Mulches?
Many studies have demonstrated the value of wood chip mulches applied to urban landscapes for improving soil quality and tree growth. Wood chips are applied annually as top dressings to the soil, at rates that are considered the current best practices for soil application.
Do Wood Chip Mulches Work?
Recent research has reported beneficial effects of wood chip mulches on soil properties related to increases in nutrient retention, soil organic matter quality, and increases in microbial activity. As expected, wood chips increased total organic carbon in most soils.
What is “Aerated Compost Tea”?
Aerated compost tea is made by aerating compost and microbial food sources in water for approximately 24 hours. Compost teas are applied directly to plants or to soils as drenches or liquid injections. Aerated compost tea is most effective if applied five times annually. The goal of an aerated compost tea program is to culture aerobic, beneficial microorganisms in the tea and then ultimately on the plants and in the soil where they are applied.
Do Aerated Compost Teas Work?
For the most part, mixed results have been reported for the effectiveness of compost teas to decrease disease and increase yield on a variety of plants. The aerated compost tea does not affect any soil properties nor make any significant differences in tree biomass. The few studies that have been performed on the effects of aerated compost tea on soil properties have found minimal impacts. One study did find the soil pH is significantly higher after aerated compost tea treatments were made.
Conclusions
It appears that biochar and biosolids are acceptable, and possibly preferable mulching materials compared with more commonly applied materials. Biosolids decreased soil pH and increased tree growth, available nitrogen, nitrogen mineralization, and microbial respiration. Increased tree growth and total organic carbon were found with biochar. Nitrate losses in leachates were minimal with all treatments, in contrast to increases in leachate dissolved organic carbon with biosolids and compost. The nitrogen content in the treatments appears to be an important predictor for tree growth except biochar, suggesting the effects of biochar for soil quality improvement are not limited to nitrogen supply. Biosolids and biochar applied to urban landscapes would divert materials from landfills and improve soil quality and tree growth.
Compaction and topsoil removal associated with site development in the city have left many soils unsuitable for growing urban trees. Consequently, soil organic matter has become much more important for growing trees in urban landscapes. What follows is a comparison of six commonly used soil mulches for growing trees in the small pits set aside in city sidewalks.
What are “Biosolid Mulches”?
Biosolids are the nutrient-rich organic materials from the treatment of sewage sludge. Biosolids have been used in reclamation of agricultural, forest, and disturbed lands since the 1960s. Studies have found the use of this material promotes increased soil fertility, improved physical properties of the soil, increased tree and forest growth, and increased microbial activity.
Some concerns associated with applying biosolids to soils include, but are not limited to, salinity, heavy metals, organic contaminants, and pathogens, as well as a poor public perception. Consequently, the US EPA requires that wastewater solids be stabilized to minimize odor generation, destroy pathogens, and reduce vector attraction. In addition, the EPA sets the ceiling and pollutant concentration levels for nutrients and metals in biosolids.
Do Biosolid Mulches Work?
The greatest increases in tree growth among the six mulches in this comparison were observed with biosolid treatments. Compared to the other five options, the total tree biomass, leaf biomass, stem biomass, and coarse root biomass were all in the best category. In addition, total organic carbon was greatest with biosolids. In most soils, nitrogen mineralization and microbial respiration was greatest with biosolids along with broad positive impacts on soil’s physical, chemical, and biological properties.
No standards currently exist for biosolid applications to urban trees, but biosolids should be applied as top-dressings or mulches at moderate rates. As a starting point, application rates for these products could be computed based on matching the nitrogen content of the material with the tree’s nitrogen demand.
Biosolids are attractive given the many potential environmental benefits. They are generated from waste products, and land applications would divert materials that may otherwise end up in landfills. More research is required regarding the persistence and toxicity of potential contaminants before implementing a biosolids program for urban trees.
What are “Biochar Mulches”?
While charcoal is used as a fuel, biochar is used as a soil amendment and was inspired by high fertility and high organic carbon contents found in anthropic soils in the Amazon Basin, referred to as Terra Preta de Indio. Today, biochar is most commonly produced through pyrolysis, which is the burning of woody biomass at 350°C to 800°C under the partial exclusion of oxygen. Biochar is generated from waste wood products and land clearing operations that divert wood materials from ending up in landfills. With products such as woody biomass, pyrolysis creates a material that is highly aromatic with carbon concentrations of 70 – 80% and it has unique properties for nutrient adsorption and stability.
Do Biochar Mulches Work?
A growing body of research is finding biochar to increase soil quality and plant growth. Biochar is also found to increase water and nutrient retention, along with increased microbial biomass and activity. In the comparison study, the total amount of organic carbon was greatest with biochar compared to the other five amendments and soil types. High amounts of tree growth, and tree biomass were found with biochar. Biochar has the additional potential benefit of carbon sequestration in the soil. No standards currently exist for biochar application to urban trees, but recent research suggests biochar can be applied annually as a top-dressing or mulch at moderate rates.
Nitrogen immobilization is a commonly raised concern with biochar. It should be noted that biochar is relatively recalcitrant, and thus the total carbon and nitrogen content may not accurately reflect what is actually available for microbial metabolism. Studies often report decreases in nutrient leaching with additions of biochar due to its high adsorption capacity. Potential negative impacts of biochar on soil quality include increasing soil pH in alkaline soils.
Urban forestry operations might be well suited for the addition of mobile, fast-pyrolysis equipment that converts urban wood waste into a bio-oil, syngas, or biochar. This equipment could be located near a biomass removal operation to convert low-value urban wood waste into easily stored and transportable fuel to be used for heat, power, and soil amendment purposes. The idea would be to generate biochar instead of creating wood chips.
What are “Compost Mulches”?
Many studies have demonstrated the value of compost applied as mulch to urban landscapes for improving soil quality and tree growth related to nutrient retention, soil organic matter quality, and microbial activity.
Do compost mulches work?
Studies are mixed about whether or not there is an increased tree growth with surface applications of compost. Most of these experiments were field based in nurseries, with larger-sized trees, and were of a long duration. In addition, these studies examined tree growth responses to compost in higher-quality soils, not in degraded soils typical of urban soil conditions. However, compost does increase the total organic carbon in all soils.
Compost should be applied annually as top dressings to the soil and at rates that are considered the current best practices for soil application.
What is “Nitrogen/Potassium Fertilizer”?
Nutrient leaching losses are a concern with both inorganic and organic fertilizers. Inorganic fertilizer salts are soluble, thus nutrients are immediately available for uptake by trees, and also thought to be more prone to leaching losses. However, nutrients may be released from organic materials at times when plant uptake is low. Tree growth is known to be limited by the nitrogen supply, especially on poorly developed soils with low fertility.
Do Nitrogen/Potassium Fertilizers Work?
Researchers found some increases in tree biomass were observed with the nitrogen/potassium fertilizer relative to the control of no treatments. This finding was expected given that inorganic fertilizers have long been used to supply nutrients for urban landscape trees. Reviews of shade tree fertilization studies, summarize the general consensus of increased tree growth with fertilization and are in agreement with other findings of increase in tree growth with the nitrogen/potassium fertilizer.
The nitrogen/potassium fertilizer (30–0–12) should be diluted with water and applied twice annually. The fertilizer applied in these treatments should be within the range of specifications for nitrogen fertilizer demands required by urban trees.
What are “Wood Chip” Mulches?
Many studies have demonstrated the value of wood chip mulches applied to urban landscapes for improving soil quality and tree growth. Wood chips are applied annually as top dressings to the soil, at rates that are considered the current best practices for soil application.
Do Wood Chip Mulches Work?
Recent research has reported beneficial effects of wood chip mulches on soil properties related to increases in nutrient retention, soil organic matter quality, and increases in microbial activity. As expected, wood chips increased total organic carbon in most soils.
What is “Aerated Compost Tea”?
Aerated compost tea is made by aerating compost and microbial food sources in water for approximately 24 hours. Compost teas are applied directly to plants or to soils as drenches or liquid injections. Aerated compost tea is most effective if applied five times annually. The goal of an aerated compost tea program is to culture aerobic, beneficial microorganisms in the tea and then ultimately on the plants and in the soil where they are applied.
Do Aerated Compost Teas Work?
For the most part, mixed results have been reported for the effectiveness of compost teas to decrease disease and increase yield on a variety of plants. The aerated compost tea does not affect any soil properties nor make any significant differences in tree biomass. The few studies that have been performed on the effects of aerated compost tea on soil properties have found minimal impacts. One study did find the soil pH is significantly higher after aerated compost tea treatments were made.
Conclusions
It appears that biochar and biosolids are acceptable, and possibly preferable mulching materials compared with more commonly applied materials. Biosolids decreased soil pH and increased tree growth, available nitrogen, nitrogen mineralization, and microbial respiration. Increased tree growth and total organic carbon were found with biochar. Nitrate losses in leachates were minimal with all treatments, in contrast to increases in leachate dissolved organic carbon with biosolids and compost. The nitrogen content in the treatments appears to be an important predictor for tree growth except biochar, suggesting the effects of biochar for soil quality improvement are not limited to nitrogen supply. Biosolids and biochar applied to urban landscapes would divert materials from landfills and improve soil quality and tree growth.
Trees, History, and Solar Energy Conflicts
Solar panels are part of an energy solution for the future while historic preservation is the key to protecting the community's past. A city’s trees are a part of the past, present, and future. Historic preservation, tree growth, and solar power generation are often part of a community's plan to become more sustainable. Tension has developed among these interests as communities struggle with how to both preserve their past and ensure a sustainable future.
The historic tree and solar interests have some notable similarities because:
Solar panels are part of an energy solution for the future while historic preservation is the key to protecting the community's past. A city’s trees are a part of the past, present, and future. Historic preservation, tree growth, and solar power generation are often part of a community's plan to become more sustainable. Tension has developed among these interests as communities struggle with how to both preserve their past and ensure a sustainable future.
The historic tree and solar interests have some notable similarities because:
- they are environmentally friendly,
- they are typically built or planted with attention to climate and air circulation,
- they are built or planted with locally sourced materials,
- they are usually located on or near walkable streets,
- they are in relatively central locations.
Historic Preservation
Preservation of historic properties is "greener" than tearing down and rebuilding because of the energy and material savings. Historical preservationists have come to an agreement that the installation of solar panels on a historic resource is generally viewed as acceptable only when they are:
Preservation of historic properties is "greener" than tearing down and rebuilding because of the energy and material savings. Historical preservationists have come to an agreement that the installation of solar panels on a historic resource is generally viewed as acceptable only when they are:
- installed on a building with a flat roof, at a low profile, and are not visible from the street,
- installed on a secondary structure and shielded from view,
- ground-mounted on non-historically significant landscapes and inconspicuously located,
- located on new buildings on historic sites or new additions to historic buildings,
- complementary to the surrounding features of the historic resource.
Historic preservation can provide a concern to the landscape architect and arborist. Trees in historic sections should be large growing species and native to the area. Any replacement trees should be similar to what were planted when the buildings were built.
Solar Panels
At the present time there are over half a million solar panels on roof tops in the United States. Many of them have the potential to come into conflict with trees that might grow and block the sun’s rays from providing maximum benefit to the solar panel. This conflict with the tree providing unwanted shade on the solar panel has come about because many people in the solar panel industry know very little about the different ways that trees grow or how large trees might become when they reach a mature size.
Landscape architects and arborists who are solar-friendly, can predict when a tree might grow to create a shadow on a solar panel. They will know how to work with the solar design people to determine the impact of increased heat from the lack of shade provided by existing trees that need pruning or removal, in exchange for increased energy from more sun on the solar panel. In addition, there are the costs necessary for repeated pruning to maintain clearance to the solar panels.
Solar-friendly arborists and landscape architects will be able to make recommendations for species selections, and placements in the historic areas. They are also able to assist developers planning to install solar panels on new or old structures. Solar-friendly arborists and landscape architects can also be a voice for homeowners seeking comfort and savings to provide shade for the property and home, while setting aside a place for the solar panels to work at peak efficiency.
Tree Shade on Solar Panels
Municipal tree preservation ordinances may have to have some flexibility or be revised to make way for this important technology. Some cities require the removal of trees that interfere with solar panels, even if the trees were planted prior to the installation of the panels or if they are growing in an historic section of the city. Additionally, many of the alternatives to tree removal recommended by solar proponents include: trimming, pruning, and height restrictions. These will all reduce the benefits that the tree canopy provides while maximizing the solar energy production.
Legal Rights to Trees, History, and Solar Energy
Laws have been adopted all over the U.S. in attempts to guarantee reasonable solar access rights in the face of the competing interests, like buildings of historic importance and large urban trees. Some cities permit local zoning authorities to adopt solar access rights in the permitting and zoning process. These rules vary in control of solar access, including consideration for shading from other structures and trees. For example:
Solar Panels
At the present time there are over half a million solar panels on roof tops in the United States. Many of them have the potential to come into conflict with trees that might grow and block the sun’s rays from providing maximum benefit to the solar panel. This conflict with the tree providing unwanted shade on the solar panel has come about because many people in the solar panel industry know very little about the different ways that trees grow or how large trees might become when they reach a mature size.
Landscape architects and arborists who are solar-friendly, can predict when a tree might grow to create a shadow on a solar panel. They will know how to work with the solar design people to determine the impact of increased heat from the lack of shade provided by existing trees that need pruning or removal, in exchange for increased energy from more sun on the solar panel. In addition, there are the costs necessary for repeated pruning to maintain clearance to the solar panels.
Solar-friendly arborists and landscape architects will be able to make recommendations for species selections, and placements in the historic areas. They are also able to assist developers planning to install solar panels on new or old structures. Solar-friendly arborists and landscape architects can also be a voice for homeowners seeking comfort and savings to provide shade for the property and home, while setting aside a place for the solar panels to work at peak efficiency.
Tree Shade on Solar Panels
Municipal tree preservation ordinances may have to have some flexibility or be revised to make way for this important technology. Some cities require the removal of trees that interfere with solar panels, even if the trees were planted prior to the installation of the panels or if they are growing in an historic section of the city. Additionally, many of the alternatives to tree removal recommended by solar proponents include: trimming, pruning, and height restrictions. These will all reduce the benefits that the tree canopy provides while maximizing the solar energy production.
Legal Rights to Trees, History, and Solar Energy
Laws have been adopted all over the U.S. in attempts to guarantee reasonable solar access rights in the face of the competing interests, like buildings of historic importance and large urban trees. Some cities permit local zoning authorities to adopt solar access rights in the permitting and zoning process. These rules vary in control of solar access, including consideration for shading from other structures and trees. For example:
- some conflicting laws ensure that the performance of a solar energy device will not be compromised by shade from vegetation or buildings on adjoining properties. Trees and some structures blocking proposed panels must be removed.
- some better laws allow a landowner to enter into an agreement with an adjacent landowner to ensure that sunlight reaches the property.
- the best laws exempt all buildings, trees and shrubs built or planted prior to the time of a solar panel's installation from being removed or severely pruned regardless of the tree’s ownership.
New Construction
While the information above is suitable for retrofitting an existing structure, developers constructing new buildings are including solar panels as part of the construction process and costs. The architects of these projects are focused on maximizing the efficiency of the solar panels while minimizing the aesthetic impact. They seldom coordinate the solar panels with the landscape design or with arborists. This could change if everyone considers the potential solutions which are described below.
Solutions
There are a number of recommendations that can assist historians, urban foresters, and solar experts in resolving future conflicts:
While the information above is suitable for retrofitting an existing structure, developers constructing new buildings are including solar panels as part of the construction process and costs. The architects of these projects are focused on maximizing the efficiency of the solar panels while minimizing the aesthetic impact. They seldom coordinate the solar panels with the landscape design or with arborists. This could change if everyone considers the potential solutions which are described below.
Solutions
There are a number of recommendations that can assist historians, urban foresters, and solar experts in resolving future conflicts:
- Ensure that the right tree is planted in the right place and for the right reason. Factors such as how tall a tree will grow at maturity, how much shade it will likely cast, and in what direction that shade will fall will help determine the optimum placement for minimizing the chance of solar conflict at a later date.
- Historians and urban foresters must become members of local solar advisory committees and councils.
- Consider creating and adopting overlay zoning for "solar access zones" in suitable areas that specifically acknowledges the need to consider building and plant size to maintain clearance for solar panels.
- Amend the subdivision ordinance to require neighborhoods and developments to be laid out in a manner that minimizes conflict between solar and trees.
- Replace removed trees where possible, and track tree removals to ensure there is no net loss in tree numbers.
- Educate citizens as to the benefits of history, solar, and trees, and increase their awareness of best practices for sensible planning to avoid shading and ensure that history, solar, and trees can coexist.
- In instances where a solar installation would result in the removal of mature trees, encourage or require other energy conservation strategies first. Additionally, encourage or require homeowners to prune trees before permitting removal to see if this might resolve potential conflict.
- Actively identify the best places to locate solar facilities in a community, and direct installations to these areas. These areas should be selected over areas that are heavily forested or areas that have historical importance.
- Incorporate planning software and tools, like i-Tree and solar maps, that provide relevant data on tree growth, urban forest benefits, and shading into the project review process. Train planning staff or hire an arborist to conduct these analyses during the review process.
- Stay on top of solar technology advancements. Encourage the development of smaller, more efficient systems, and encourage or require the selection of systems that are least impacted by shading (when shading is unavoidable).
The American Standard for Nursery Stock
American Standard for Nursery Stock provides buyers and sellers of nursery stock uniform sizes and a common terminology in order to standardize all sales of nursery stock. It does not provide buyers with any assurance of the health or quality of the nursery stock being specified or sold. The 2004 edition of the American Standard for Nursery Stock (ANSI Z60.1 – the Standard) has been revised and the 2014 edition just been released for use. These revisions include several improvements to fix problems that arborists have been complaining about for the past ten years. Click here for the 2014 Edition of the Standard.
Changes in the 2014 Edition
There have been several important changes to the standards compared to the 2004 edition. Landscape architects and arborists need to be aware of the changes in this latest edition. Some of these major changes include:
1. New tables for each plant type should make the Standard easier to use. The tables include:
- the minimum root ball size,
- various measurement ratios such as caliper to height and spread to height,
- the minimum number of branches,
- minimum container class,
- tree size being grown in in-ground fabric bags.
2. Minimum requirements for all nursery stock in a new “General Standards” section include:
- identification by genus, species, and cultivar,
- living condition,
- form or shape for the species or cultivar,
- an indication that the plant or tree is free of damaging insects and diseases,
- pruning cuts must be done in accordance with pruning standards,
- shade trees may not have co-dominant stems in the bottom half of the crown,
- eliminate repeating the standards text in several sections and the Foreword of the 2004 edition.
3. Clarification of the method for measuring caliper and the relationship between the root flare and the soil
line.
4. Changes to specifications to allow in-ground fabric bags and expansion of their application to all plants and trees.
5. Recognition of containers that encourage fibrous root growth.
6. Recognition of fabric as an acceptable container material.
7. The plant type tables are separate and according to plant type, by plant size interval, including minimum root ball diameters and depths, various measurement ratios, minimum number of branches, minimum and
maximum container classes, and minimum in-ground fabric bag size.
8. The new plant type tables provide minimum and maximum container size range for each plant size interval.
line.
4. Changes to specifications to allow in-ground fabric bags and expansion of their application to all plants and trees.
5. Recognition of containers that encourage fibrous root growth.
6. Recognition of fabric as an acceptable container material.
7. The plant type tables are separate and according to plant type, by plant size interval, including minimum root ball diameters and depths, various measurement ratios, minimum number of branches, minimum and
maximum container classes, and minimum in-ground fabric bag size.
8. The new plant type tables provide minimum and maximum container size range for each plant size interval.
Revised Definitions
Growers know that trees with measurements beginning 6 inches above the root flare at or near the soil line will have larger caliper and height measurements than trees with primary structural roots buried well below the soil line and, therefore, they will have a higher value in the marketplace. In this regard, text has been added to clarify that measuring caliper shall begin at the root flare.
In addition, the caliper “4 inch” size has been revised to include the entire interval up to but not including 4½ inches. If the caliper measured at 6 inches above the root flare is 4½ inches or more, the caliper shall instead be measured at 12 inches above the root flare.
Minimum Sizes for Sheared Evergreens
The new evergreen plant type tables remove the cross-reference to the shade tree table for determining minimum root ball diameter eliminating inconsistent minimum root ball specifications for sheared and non-sheared evergreens of the same caliper.
Fabric Bags Revisions
Clarification throughout the 2014 edition indicates that all references are to “in-ground” fabric bags. They are sized 5-inch and 8-inch. There are also in-ground fabric bags sized over 24-inches in diameter. There are also smaller depth minimums for in-ground fabric bag sizes.
The new edition recognizes that fabric is an acceptable material for “above-ground” containers, as long as the root system meets the general requirement for container-grown nursery stock.
Growers know that trees with measurements beginning 6 inches above the root flare at or near the soil line will have larger caliper and height measurements than trees with primary structural roots buried well below the soil line and, therefore, they will have a higher value in the marketplace. In this regard, text has been added to clarify that measuring caliper shall begin at the root flare.
In addition, the caliper “4 inch” size has been revised to include the entire interval up to but not including 4½ inches. If the caliper measured at 6 inches above the root flare is 4½ inches or more, the caliper shall instead be measured at 12 inches above the root flare.
Minimum Sizes for Sheared Evergreens
The new evergreen plant type tables remove the cross-reference to the shade tree table for determining minimum root ball diameter eliminating inconsistent minimum root ball specifications for sheared and non-sheared evergreens of the same caliper.
Fabric Bags Revisions
Clarification throughout the 2014 edition indicates that all references are to “in-ground” fabric bags. They are sized 5-inch and 8-inch. There are also in-ground fabric bags sized over 24-inches in diameter. There are also smaller depth minimums for in-ground fabric bag sizes.
The new edition recognizes that fabric is an acceptable material for “above-ground” containers, as long as the root system meets the general requirement for container-grown nursery stock.
Recognition of Certain Containers
The new edition recognizes that certain containers are now generally accepted in the nursery trade as a type that are designed to promote fibrous root growth by root pruning and root training. The fabric container and a well-developed root system work together to hold the ball shape and protect the integrity of the root system during handling even though the fabric container standing alone is not a rigid pot. Because of this, the new edition eliminates the requirement that the container shall be sufficiently rigid to hold the ball shape and protect the root mass during shipping. The revised version also recognizes and approves containers that encourage or manipulate fibrous root growth. These containers:
- use holes or fabric aeration to prune roots,
- may have coatings to prevent roots from reaching the sides of the container,
- may be a shape that trains roots to go in a certain direction.
Plan to use this new standard soon to obtain higher quality nursery stock.
Sources
Sources
- Scharenbroch, Bryant C. et.al. “Biochar and Biosolids Increase Tree Growth and Improve Soil Quality”, 2014.
- “Balancing Solar Energy Use with Potential Competing Interests”, American Planning Association Planning Advisory Service. 2011.
- Staley, Daniel C., “Your Next Opportunity: Solar-friendly Tree Care”, Tree Care Industry, July 2014.
- AmericanHort, “American Standard for Nursery Stock”, 2004 & 2014.
- Warren Quinn, “Production playbook”, Nursery Management, May 2014.
The test that follows contains 30 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
LA CES will award 1.0 PDH (HSW) credit for a passing grade. North Carolina Board of LA and New Jersey Board of Architects have approved this course for 1.0 credit.
The cost for taking this test is $20 per credit. If you purchase an annual subscription for 12 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report your passing test score to LA CES. If you are also ISA* certified we will report your passing score to ISA for no additional cost. Please be sure to add your ISA Certification number when you sign in. Tests with passing scores may be submitted only once to each organization.
*ISA has approved this course for .5 CEUs per section for a total of 1.5 CEUs applied toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, or .5 BCMA Science credits and 1.0 BCMA Management credits.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to gibneyCE.com’. That will take you to the test sign in page followed by the test. If you are an ISA and/or CLARB member, please be sure to include your certification/member number(s) along with your LA license and ASLA numbers.
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 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. 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.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option.
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.
LA CES maintains a record of earned PDH credits on their website http://laces.asla.org/
ISA maintains a record of earned CEU credits on their website http://www.isa-arbor.com/