#7 Read About Bare Root Trees
Edited by Len Phillips, updated January 2023
Sections You may go directly to the section by clicking on titles listed here.
Edited by Len Phillips, updated January 2023
Sections You may go directly to the section by clicking on titles listed here.
Click on the green text in each section for more information
Bare Root (BR) trees are dug and stored without any soil around their roots. BR trees are available as deciduous dormant trees typically 2-inch (5 cm) trunk diameter or less. BR trees are very sensitive to drying if not properly stored and shipped. If provisions are made to keep roots in the shade and moist during storage and transport and they are regularly watered after installation, they perform as well as, if not better than trees from all other production methods.
Tips for Bare Root Tree Installation
Bare root is about as basic as trees come. They are affordable, simple to handle and a bare-root tree contains 200% more roots than the same tree growing in a container. It has also been demonstrated that a bare-root tree, once installed at a new location, will establish and grow at double the rate of a B&B or containerized tree right next to it.
What are the advantages of installing bare root trees?
What are the disadvantages of installing bare root trees?
What are the best techniques to follow for bare root tree installation?
Why hasn't everyone switched to bare root installation?
With municipal tree installations there is an inevitable holding period between digging the trees and installing them. During this period, root desiccation is the most critical disadvantage to installing bare root trees. In the past, people put wet straw around the roots or coated them in a mud slurry. These methods did not prove satisfactory or practical; the straw did not protect fine roots adequately and the mud slurry tended to dry out and chip off or break the root. Now however, a synthetic, non-toxic water-absorbing compound called hydrogel solves the desiccation problem for that critical time between digging and replanting. Installing the trees temporarily in Missouri gravel beds (see the description at the end of this Topic) or wood chip beds and providing irrigation have proven to be successful in keeping the trees alive and healthy between the time of digging to the time of installation.
Installation Tips
Bare root is about as basic as trees come. They are affordable, simple to handle and a bare-root tree contains 200% more roots than the same tree growing in a container. It has also been demonstrated that a bare-root tree, once installed at a new location, will establish and grow at double the rate of a B&B or containerized tree right next to it.
What are the advantages of installing bare root trees?
- More root mass. Bare root trees can have up to 200% more roots than B&B trees, depending on the soil and transplanting history at the nursery. The reason for this is the harvesting machinery for bare root trees digs a much larger root system than the tree spade used for B&B digging. Plus, with bare root trees you won't rob nurseries of their valuable field soil.
- Lower cost. You can install more trees, inexpensively. Without extra labor and materials, bare root trees cost the seller and buyer less. Bare root trees are one-half as expensive as B&B trees. Because they are so much lighter and many more can fit on the bed of a truck, they are also cheaper to ship.
- Easier installation. A young tree without soil weighs little, so it is easy to move and install. Installing a bare root tree costs virtually nothing when done by volunteers with shovels.
What are the disadvantages of installing bare root trees?
- Less time. Once they leave the nursery, bare root trees need to get in the ground or be in long-term storage within a week at the longest. With no soil or water, the roots can dry out and die if left exposed for any time more than an hour.
- Narrower installation window. Bare root trees need good soil moisture, so mid spring (before bud break) and mid autumn (after leaf drop) are the best two installation times.
- Restricted availability. Some species may not be available bare root, and some nurseries may not have trees available for bare root sale at all.
- Potential to blow over. Without the mass of soil around the roots, there is a perception that the tree could easily blow over in high winds. However with the use of new tree stabilizing devices that hold the roots to the bottom of the planting hole, it is highly unlikely this will happen. See Archived Seminar #69 - Best Way to Stabilize Trees Section
What are the best techniques to follow for bare root tree installation?
- Use any technique you can to reduce the time the tree roots are bare.
- Order 1½" – 2" trees to be dug within 24 hours of pickup at the nursery, otherwise be sure they are stored in a cool place where the roots can be protected from sun and wind.
Why hasn't everyone switched to bare root installation?
With municipal tree installations there is an inevitable holding period between digging the trees and installing them. During this period, root desiccation is the most critical disadvantage to installing bare root trees. In the past, people put wet straw around the roots or coated them in a mud slurry. These methods did not prove satisfactory or practical; the straw did not protect fine roots adequately and the mud slurry tended to dry out and chip off or break the root. Now however, a synthetic, non-toxic water-absorbing compound called hydrogel solves the desiccation problem for that critical time between digging and replanting. Installing the trees temporarily in Missouri gravel beds (see the description at the end of this Topic) or wood chip beds and providing irrigation have proven to be successful in keeping the trees alive and healthy between the time of digging to the time of installation.
Installation Tips
- Bare root trees should be dug during the dormant season.
- Be sure the nursery has tied the branches up with twine to prevent breakage in transit.
- Keep trees covered, shaded, and moist until actually putting them in the ground.
- Snip off any broken roots, then put the tree in a bucket of water for 12 to 24 hours before installation.
- Add a growth stimulant to the bucket of water to kick-start root growth or dip tree roots in a slurry of a hydrogel, then store them in large, pleated plastic bags until installation.
- Label each tree with its intended location or address before it gets dipped and bagged so that when the labor force picks up the trees for installation, they can simply go to the location on the label. You may also want to label the tree's scientific name, its common name, and the date of installation, just so the person installing the tree can answer any questions from the public or homeowner, when the tree is being planted.
- The installation hole should be no deeper than the root system, but at last three times as wide. The best hole digger is a backhoe that makes a simple shallow, saucer-shaped, hole, perfect for the tree. The teeth on the bucket should dig into the bottom of the hole so the soil will be a little loose for new roots to grow into.
- Depending on the tree's root system, a second option is to make a cone of soil to rest the tree on and get the tree to the right height with the root flare (where the roots meet the trunk) is at one inch above the finished grade level.
- Spread the roots out evenly over the installation area.
- Fill in the installation hole with the soil just removed to cover the roots and then add water to be sure the roots are in contact with soil.
- Do not try to improve the soil with amendments, such as compost unless the soil test indicates there is a problem. Roots would have a tendency to stay in the fluffy amended soil and the tree can become root-bound. Filling a hole with amended soil can also create drainage problems. Water tends to stay in the amended area and when the roots get waterlogged, the tree will die.
- When you have replaced half of the backfill, water the entire planting area to help collapse air pockets. Firm the soil with the wood end of your shovel to gently poke out air pockets or lift and lower the tree gently to work the wet soil around the roots. Do not use your foot. You do not want heavy compaction around the roots. If the tree will not stand up straight, do not use your foot to push down on the high side. Lift the tree up on the low side and replant it or use a “tree staple” type device to hold the root firmly down.
- Finish backfilling and gently firm the soil by hand, not your foot! Make sure the soil is not mounded against the trunk and that the beginning of the flare is showing above the ground level.
- Make a saucer, about 3 feet (1m.) in diameter around the tree and fill it with water. The water should seep in slowly and reach the depth of the roots. Be sure the tree stays hydrated for the first 24 hours.
- Cover the basin with wood chips or shredded bark mulch to retain moisture and control weeds, but don't put mulch right next to the trunk.
- Three to four inches thick is a good depth for mulch.
- Consider investing in tree irrigator bags. They hold 20 gallons of water and slowly release it to the roots, saving watering time and aiding in tree establishment.
- Fertilizer is not recommended for newly installed trees.
- Trunk stabilizing is not necessary and can even be detrimental for most young trees. The exceptions are an extremely windy site, a tree with an unusually small root system, an unusually large canopy relative to a tree's root system, a tree whose trunk is seriously bowed, or in high traffic areas where vandalism is feared. If stabilizing is necessary, root stabilizers should be installed.
A Bare Root Tree Installation Program that Saves Money
Installing trees in communities can be costly and labor intensive due to the size of the tree (12-15 ft. tall, 2" caliper) (3.6 - 4.6 m tall, 5 cm caliper) that is required to assure survival on a street. The standard transplanting method, called balled and burlapped (B&B), contains a soil and root ball weighing about 300 pounds (140 kg), and usually requires heavy equipment to dig the planting hole and lift the tree, plus trained labor is required to install the tree at a site. During the digging process for B&B trees, approximately 95% of the tree's root system is cut off and left in the nursery, putting these trees under stress or "transplant shock" for a few years.
With limited funds, managers of community tree programs must make their dollars go further, use volunteers, and show good tree survival if their program is to be sustained by the community with local tax dollars. Instead of installing a few trees B&B, communities are now installing trees bare root.
A good example of making tree planting funds go further, began in 1998, when Extension Urban Forester Vincent Cotrone held a Community Forestry Conference in northeastern Pennsylvania where Dr. Nina Bassuk, Professor of Horticulture at Cornell University, explained her research involving a method of transplanting trees bare root. She explained that transplanting trees bare root is nothing new, but by dipping the root systems in a hydrogel and bagging them in large plastic bags immediately after digging, they were protected from drying out. These bare root trees had 200% more roots than B&B, which meant better survival and establishment of the trees, once properly installed. With the assistance of Extension Urban Forester Cotrone, two communities from Sullivan County decided to try bare root trees in the autumn of 1998, and drove to the nursery together to pick them up.
The extension urban forester quickly saw this pilot project turn into an annual spring and autumn project of working closely with 15 – 18 communities in northeast PA, to select appropriate trees for their streets or parks and then helping to procure the bare root trees in one large group order. By grouping the orders together, communities saved lots of money in purchasing and shipping costs. In fact, in 2011, the shipping costs were $3 per tree.
Work begins in December and January, preparing orders for bare root trees for the spring installation. A community can order from 10 to 150 trees but must be prepared to pick them up at a drop off site in Pennsylvania. Working closely with the nursery in upstate New York, their digging schedules, and weather, the extension urban forester notifies each community contact person about one week before delivery in mid-April. On delivery day, a refrigerated tractor-trailer arrives at the preplanned site (usually a municipal public works garage) and volunteers unload, check the orders, and sort all the trees as they are redistributed and packed into smaller trucks for a short drive to the appropriate communities. Municipal tree commissions then utilize trained volunteers or public works staff to get the trees installed and watered within 7-10 days, before they break bud. If the roots dry out before they are installed or break bud, the trees will probably die.
In total, since 2011 these communities have saved a total of approximately US $1 million (assuming a $250 cost to purchase and install a B&B tree), making it possible to install and care for many more community trees than an order of B&B trees. The nursery bills the community for their trees directly. The nursery is Schichtel's Nursery in upstate NY. At the time of writing this article, there are apparently no nurseries in PA interested in selling bare root trees.
A great deal of work goes into planning this type of tree purchase and arranging for drop-off/pick-up locations, but the project has done more than saving dollars. The project trains community volunteers how to properly install and care for these trees, and these volunteers in-turn, become long-term stewards of the community forest. It has been an extremely beneficial activity that helps build community pride and cooperation within the region. Other states in the nation have been inquiring about how PA plans and implements this group tree purchase.
In the past few years, this program has been expanded to southeastern Pennsylvania, organized by the Pennsylvania Horticultural Society with assistance from Julianne Schieffer, Penn State Extension Urban Forester in southeastern Pennsylvania.
In order to continue to provide this service and take advantage of bare root trees, both in cost savings and with labor savings, there are several requirements that the communities must follow for each year's bare root tree order:
The major benefits of bare root installation include:
The communities must develop watering programs for the bare roots, something they might not have done if a contractor installed and maintained trees B&B. They also use volunteers, saving money and better yet, involving the community residents in urban forestry. The communities work together because of the group orders. They will help each other transport trees, or install trees, etc.
The only downside is that certain species transplant well bare root and some do not. Researchers are trying new ones all the time and Cornell has developed lists of trees and their tolerance to BR installation.
As with all new tree installations, keep in mind the need to provide each tree with 10 to 20 gallons of water per week, rain or shine. The first year in the ground, the bare root trees will have sparse growth and smaller than normal leaves. In year two, the trees will look very good (if installed properly and watered) since they actually have more roots than B&B trees. By the third year, the trees should be growing at a rate equal to or greater than before the tree was dug at the nursery.
Installing trees in communities can be costly and labor intensive due to the size of the tree (12-15 ft. tall, 2" caliper) (3.6 - 4.6 m tall, 5 cm caliper) that is required to assure survival on a street. The standard transplanting method, called balled and burlapped (B&B), contains a soil and root ball weighing about 300 pounds (140 kg), and usually requires heavy equipment to dig the planting hole and lift the tree, plus trained labor is required to install the tree at a site. During the digging process for B&B trees, approximately 95% of the tree's root system is cut off and left in the nursery, putting these trees under stress or "transplant shock" for a few years.
With limited funds, managers of community tree programs must make their dollars go further, use volunteers, and show good tree survival if their program is to be sustained by the community with local tax dollars. Instead of installing a few trees B&B, communities are now installing trees bare root.
A good example of making tree planting funds go further, began in 1998, when Extension Urban Forester Vincent Cotrone held a Community Forestry Conference in northeastern Pennsylvania where Dr. Nina Bassuk, Professor of Horticulture at Cornell University, explained her research involving a method of transplanting trees bare root. She explained that transplanting trees bare root is nothing new, but by dipping the root systems in a hydrogel and bagging them in large plastic bags immediately after digging, they were protected from drying out. These bare root trees had 200% more roots than B&B, which meant better survival and establishment of the trees, once properly installed. With the assistance of Extension Urban Forester Cotrone, two communities from Sullivan County decided to try bare root trees in the autumn of 1998, and drove to the nursery together to pick them up.
The extension urban forester quickly saw this pilot project turn into an annual spring and autumn project of working closely with 15 – 18 communities in northeast PA, to select appropriate trees for their streets or parks and then helping to procure the bare root trees in one large group order. By grouping the orders together, communities saved lots of money in purchasing and shipping costs. In fact, in 2011, the shipping costs were $3 per tree.
Work begins in December and January, preparing orders for bare root trees for the spring installation. A community can order from 10 to 150 trees but must be prepared to pick them up at a drop off site in Pennsylvania. Working closely with the nursery in upstate New York, their digging schedules, and weather, the extension urban forester notifies each community contact person about one week before delivery in mid-April. On delivery day, a refrigerated tractor-trailer arrives at the preplanned site (usually a municipal public works garage) and volunteers unload, check the orders, and sort all the trees as they are redistributed and packed into smaller trucks for a short drive to the appropriate communities. Municipal tree commissions then utilize trained volunteers or public works staff to get the trees installed and watered within 7-10 days, before they break bud. If the roots dry out before they are installed or break bud, the trees will probably die.
In total, since 2011 these communities have saved a total of approximately US $1 million (assuming a $250 cost to purchase and install a B&B tree), making it possible to install and care for many more community trees than an order of B&B trees. The nursery bills the community for their trees directly. The nursery is Schichtel's Nursery in upstate NY. At the time of writing this article, there are apparently no nurseries in PA interested in selling bare root trees.
A great deal of work goes into planning this type of tree purchase and arranging for drop-off/pick-up locations, but the project has done more than saving dollars. The project trains community volunteers how to properly install and care for these trees, and these volunteers in-turn, become long-term stewards of the community forest. It has been an extremely beneficial activity that helps build community pride and cooperation within the region. Other states in the nation have been inquiring about how PA plans and implements this group tree purchase.
In the past few years, this program has been expanded to southeastern Pennsylvania, organized by the Pennsylvania Horticultural Society with assistance from Julianne Schieffer, Penn State Extension Urban Forester in southeastern Pennsylvania.
In order to continue to provide this service and take advantage of bare root trees, both in cost savings and with labor savings, there are several requirements that the communities must follow for each year's bare root tree order:
- A minimum order of ten (10) trees
- A community representative must be present at the delivery site to help unload bare root trees and load their order for transport to their community.
- All bare root tree orders are to be processed through the Extension Urban Forester in order to coordinate shipment and drop-off locations. The extension urban forester should be informed of all bare root tree orders and changes made to orders with the nursery.
- Bare root tree harvesting is weather dependent. The Extension Urban Forester will be notified by the nursery as to the dates of harvesting and shipping. Delivery of trees can vary from the middle of April to early May for spring installation and the first two weeks of November for autumn installation.
- The Extension Urban Forester will determine the drop-off locations based upon number of communities ordering trees, number of trees ordered by each community, the total number of trees ordered, and the number of trucks needed for delivery.
- For communities who have not installed bare root trees, "Creating an Urban Forest: The Bare Root Planting Method", a large PDF file and the video indicated in the third paragraph of this section and is from Cornell University, illustrate the bare root installation method and its many benefits. Either one of these should be viewed and used for training community volunteers.
- To participate, membership in the Pennsylvania Urban and Community Forestry Council is required. The Council provides financial support for the Extension Urban Forestry Program and produces the magazine "Sylvan Communities".
The major benefits of bare root installation include:
- more roots,
- a visible flare so the proper installation depth can be achieved,
- volunteers can easily carry two low weigh trees to the planting site,
- cost savings for the tree and the shipping,
- good survival rates.
The communities must develop watering programs for the bare roots, something they might not have done if a contractor installed and maintained trees B&B. They also use volunteers, saving money and better yet, involving the community residents in urban forestry. The communities work together because of the group orders. They will help each other transport trees, or install trees, etc.
The only downside is that certain species transplant well bare root and some do not. Researchers are trying new ones all the time and Cornell has developed lists of trees and their tolerance to BR installation.
As with all new tree installations, keep in mind the need to provide each tree with 10 to 20 gallons of water per week, rain or shine. The first year in the ground, the bare root trees will have sparse growth and smaller than normal leaves. In year two, the trees will look very good (if installed properly and watered) since they actually have more roots than B&B trees. By the third year, the trees should be growing at a rate equal to or greater than before the tree was dug at the nursery.
Fibrous Root System Development
Trees generally do poorly in city planting spaces for a number of reasons but especially poor quality soils and insufficient soil volume for root growth to sustain the tree following installation. Often trees may have a good natural root system and are inefficient in utilizing what little soil is available in the urban site.
Many people have heard the expression “Do not plant native trees unless they are being planted in native soil”. While this expression was intended to be an argument in favor of planting cultivars in urban soil instead of native trees, it can also be applied to all trees that do not have root systems suited for growing in urban soils and perhaps trees with fibrous roots should be selected over trees with natural root systems. What is important is to choose trees for city plantings that are tolerant to soils with limited oxygen, water, microorganisms, and nutrient availability. This is why trees with fibrous roots and species such as sycamore (Platanus) and red maple (Acer rubrum), which are native to stream banks and wet soils, do so well in cities.
Advantage of Fibrous Roots
Trees with fibrous root systems and many active white root-tips (root hairs) at the time of installation have a much greater likelihood of success in exploiting any favorable soil that exists in the planting pit. Research indicates that trees grown with fibrous, shallow root systems have the capacity to function well in restricted urban spaces for a much longer period of time than conventional field grown trees because the fibrous roots can take advantage of the limited soil amenities.
In other words, establishment of a newly installed tree in an urban location is clearly hastened by a fibrous root system. In the long-term, the more roots the tree produces at the installation site, the better chances that the tree will have an extended life by 20% to 50% compared to conventionally grown trees. In addition, when a tree is supported by 500 small roots versus 20 large roots, none of the 500 roots will grow large in diameter and damage the hardscape at the surface but these small 500 will be able to find the water, nutrients, and other resources needed to survive and grow.
Root Development
When a seed germinates in the forest, a strong taproot, plunges downward into the soil. The tip of the taproot has a strong dominance that suppresses secondary root branching. The objective of the taproot is to extend deeply to anchor the new plant and access moisture to avoid dehydration. Only after the taproot is secured and is providing water and nutrients, and the new leaves are producing energy to a tree, does appreciable secondary branching begin to occur to stems above and roots below ground. Similarly, a rooted cutting does not have a primary or tap-root, but the secondary roots stimulated on a cutting are typically no more fibrous than on a seedling that has been air-pruned at a 4-inch depth.
In urban soils however, trees are not able to follow this normal taproot to secondary root branching development because of compaction, lack of micro-organisms, nutrients, water, and poor quality soil. Therefore root systems should be modified at the nursery, to be better suited for growth in urban soils. The answer is quite simply, encourage the development of fibrous root systems. This is the place where the greatest benefits can be provided for trees forced to grow in urban conditions.
This begs the question, while the fibrous roots are fine for feeding, what about structural stability? Will these roots be sturdy enough for the tree to stand during a very high wind? Researchers have responded to this concern by asking the question – which is stronger, a ½ inch solid steel rod or a ½ inch braided cable composed of many small units. Obviously the cable is much stronger.
Nursery Conditions
Growing conditions in the nursery are very different from the city soils because adequate moisture and nutrients are provided. There is no need for a deep taproot. When the taproot is pruned at the proper time and position, horizontal secondary roots are produced and it is highly desirable to maintain these roots in the horizontal position.
Large strides in the nursery industry have been made in soil-less mixes, micro-nutrient applications, slow release N-P-K fertilizers, weed control, watering systems, and more. Having a fibrous root system throughout the growth medium improves water use efficiency, absorption of nutrients, and reduces nutrient leaching. In addition, roots are more insulated from extremes of heat and cold, and plants establish more rapidly. But the most important reason to have fibrous roots is because they can quickly adapt to the extremes of urban soil.
Creating Fibrous Root Systems
Fibrous root systems can be consistently created by air-pruning the tip of the taproot approximately 4" below the seed. Some nurseries achieve root pruning by using bottomless containers and constantly shifting the container. As soon as the root structure has filled one bottomless container, the plant is transplanted to the next larger size and the root pruning process is repeated. The RPM (Root Production Method) system developed at Forrest Keeling Nursery uses this concept to produce trees ranging from three to six feet tall in just eight months, depending on species.
Fibrous Root Producing Containers
Currently, there are eight options to force a root system to become fibrous:
The first methods of root pruning mentioned above have been in commercial use since the first air pruning began with Dr. Carl Whitcomb's research in 1969. Refinements of these products began in the 80's and continue to this day. The first fabric container designed to be used in the ground and cause constriction pruning was done with the Root Control Bag in 1980. The first grow-bag appeared in 1983.
Newest Products
One new product, RootMaker® propagation tray is an injection-molded container of various sizes with a series of saw-tooth like ledges and openings on the sides and bottom for air-root-pruning. Seeds planted in these propagation containers develop roots in all directions, not just down.
Another effective air-root-pruning product is a line of fabric aeration containers, called Smart Pots® that use a porous black fabric to cool the soil by evaporating soil water with air movement. When this happens, salts accumulate on the container surface from both fertilizers and irrigation water. This causes the fabric containers to have a white residue develop over months or years. Even algae growth on the sides provide an added benefit for less watering and keeping the root ball cooler.
Advantages of Fibrous Root Producing Containers
With smooth-walled conventional containers, roots become concentrated and congested against the inner sidewall with little root exploration into the central volume of the container. Once that inner sidewall area is exploited, root exploration and nutrient mining is restricted and the tree begins to stagnate and decline. These new types of containers eliminate this problem.
Disadvantages
There are some disadvantages of fibrous rooting products:
- Specifying and stating the size of plants
- Relationship among caliper, height, branch number
- Size of root ball, container, or box
Tree Installation
Trees raised in any of the containers mentioned can be installed directly from the container. Proper tree planting techniques must be followed even with all the advantages of fibrous roots.
Conclusion
With timely air-root-pruning of seedlings and cuttings, and provisions for continued horizontal root development, trees can be consistently produced with highly efficient fibrous root systems that extend in all directions following transplanting. They establish more quickly following transplanting because they more efficiently utilize the volume of soil available with their many small roots. Trees grown this way may require root stabilizing or staking during the first growing season after final installation. The greater the support of roots for the shoots, the faster both shoots and roots grow and the healthier the tree, regardless of the soil conditions.
Trees generally do poorly in city planting spaces for a number of reasons but especially poor quality soils and insufficient soil volume for root growth to sustain the tree following installation. Often trees may have a good natural root system and are inefficient in utilizing what little soil is available in the urban site.
Many people have heard the expression “Do not plant native trees unless they are being planted in native soil”. While this expression was intended to be an argument in favor of planting cultivars in urban soil instead of native trees, it can also be applied to all trees that do not have root systems suited for growing in urban soils and perhaps trees with fibrous roots should be selected over trees with natural root systems. What is important is to choose trees for city plantings that are tolerant to soils with limited oxygen, water, microorganisms, and nutrient availability. This is why trees with fibrous roots and species such as sycamore (Platanus) and red maple (Acer rubrum), which are native to stream banks and wet soils, do so well in cities.
Advantage of Fibrous Roots
Trees with fibrous root systems and many active white root-tips (root hairs) at the time of installation have a much greater likelihood of success in exploiting any favorable soil that exists in the planting pit. Research indicates that trees grown with fibrous, shallow root systems have the capacity to function well in restricted urban spaces for a much longer period of time than conventional field grown trees because the fibrous roots can take advantage of the limited soil amenities.
In other words, establishment of a newly installed tree in an urban location is clearly hastened by a fibrous root system. In the long-term, the more roots the tree produces at the installation site, the better chances that the tree will have an extended life by 20% to 50% compared to conventionally grown trees. In addition, when a tree is supported by 500 small roots versus 20 large roots, none of the 500 roots will grow large in diameter and damage the hardscape at the surface but these small 500 will be able to find the water, nutrients, and other resources needed to survive and grow.
Root Development
When a seed germinates in the forest, a strong taproot, plunges downward into the soil. The tip of the taproot has a strong dominance that suppresses secondary root branching. The objective of the taproot is to extend deeply to anchor the new plant and access moisture to avoid dehydration. Only after the taproot is secured and is providing water and nutrients, and the new leaves are producing energy to a tree, does appreciable secondary branching begin to occur to stems above and roots below ground. Similarly, a rooted cutting does not have a primary or tap-root, but the secondary roots stimulated on a cutting are typically no more fibrous than on a seedling that has been air-pruned at a 4-inch depth.
In urban soils however, trees are not able to follow this normal taproot to secondary root branching development because of compaction, lack of micro-organisms, nutrients, water, and poor quality soil. Therefore root systems should be modified at the nursery, to be better suited for growth in urban soils. The answer is quite simply, encourage the development of fibrous root systems. This is the place where the greatest benefits can be provided for trees forced to grow in urban conditions.
This begs the question, while the fibrous roots are fine for feeding, what about structural stability? Will these roots be sturdy enough for the tree to stand during a very high wind? Researchers have responded to this concern by asking the question – which is stronger, a ½ inch solid steel rod or a ½ inch braided cable composed of many small units. Obviously the cable is much stronger.
Nursery Conditions
Growing conditions in the nursery are very different from the city soils because adequate moisture and nutrients are provided. There is no need for a deep taproot. When the taproot is pruned at the proper time and position, horizontal secondary roots are produced and it is highly desirable to maintain these roots in the horizontal position.
Large strides in the nursery industry have been made in soil-less mixes, micro-nutrient applications, slow release N-P-K fertilizers, weed control, watering systems, and more. Having a fibrous root system throughout the growth medium improves water use efficiency, absorption of nutrients, and reduces nutrient leaching. In addition, roots are more insulated from extremes of heat and cold, and plants establish more rapidly. But the most important reason to have fibrous roots is because they can quickly adapt to the extremes of urban soil.
Creating Fibrous Root Systems
Fibrous root systems can be consistently created by air-pruning the tip of the taproot approximately 4" below the seed. Some nurseries achieve root pruning by using bottomless containers and constantly shifting the container. As soon as the root structure has filled one bottomless container, the plant is transplanted to the next larger size and the root pruning process is repeated. The RPM (Root Production Method) system developed at Forrest Keeling Nursery uses this concept to produce trees ranging from three to six feet tall in just eight months, depending on species.
Fibrous Root Producing Containers
Currently, there are eight options to force a root system to become fibrous:
- Air-root-pruning – This technique allows air to prune the roots as they reach the bottom and later the sides of the growing container. The desiccated root-tips have effectively been cauterized and are unlikely to be colonized by pathogens. Young seedlings respond by developing fibrous absorbing roots laterally in the container. Effective air-root-pruning containers such as the RootMaker® guide root-tips into the numerous openings so small that rapid evaporation and salt accumulation do not become an issue. The High Caliper Smart Pot Pro®, a fabric container, has 100% aeration due to the nature of the fabric that allows for the roots to reach the sides of the bag and lets the oxygen dry the root tip causing the root to branch from the outside in for a very fibrous system with no circling of the roots.
- Root-constriction – Roots can be constricted while trying to grow through a fabric. This pruning is effectively accomplished in field soil where roots are allowed to grow through a fabric container wall. In this RootMaker® Knit Fabric container, or the Root Control In-Ground product, young root-tips extend freely through the fabric, but as soon as they increase in diameter ever so slightly they become girdled. Because the roots are young and actively growing, the choking causes the root to lose its apical dominance and lateral branching occurs inside the bag. However, the constriction minimizes or prevents the downward movement of sugars from the leaves from going beyond the inside wall of the fabric. This accumulation of sugars causes nodules to form that have many root buds. When the fabric is removed and the tree is installed in its final home, robust root growth appears from these nodules.
- Root-tip-trapping –Roots can be forced to branch behind a point where the root-tip is snagged in a fabric sufficiently enough to impede growth. Root pruning is accomplished in the RootTrapper® container and the Smart Pot Pruner as the root-tips contact the fuzzy inside fabric and can no longer extend. The trapped root-tip will typically stop elongating, become pudgy, and then lose hormonal control over root development, resulting in secondary branch roots. The advantage of this root-pruning technique is that the roots do not circle, no water is lost through the container sidewall, and roots are fully contained, even when the container is in the ground or inside another container. One product uses a spun-bonded fabric laminated on the outside with white plastic. When used in an above ground container, the insulating value of such fabrics reduces root zone temperatures by about 20° F (10 C). This allows root growth on the side of the container exposed to sun and avoids the problems that arise when roots are killed by absorbed heat from a black container.
- Herbicide – This lesser used option has herbicide pellets attached at intervals within a fabric container. Root-tips that contact the herbicide die, causing branching to occur behind that point. These containers are not widely used in the nursery industry any more due to a stunting problem caused by the herbicide.
- Copper – Copper is painted on the inside of a plastic container. The copper is toxic to roots, so root pruning occurs. Misuse of copper can be toxic to humans and the soil, so extra care should be taken when using these products. Copper treated containers are now falling out of favor due to the toxicity.
- Mechanical Root Pruning –Large trenching-type machines can chop the roots of field grown trees, which cause branching at the cut. The trees are then dug, balled, and burlapped. Some nurseries partially hand dig a few months before harvest to promote root branching.
- Light –Some fabric containers root prune by a combination of light and air. However, light has no adverse effect on roots. Expose most roots to light and they will begin to form a bark-like covering, but are not impeded in any way, unless they are allowed to dry out.
- Root Suffocation –Roots growing in containers with water reservoirs in the bottom are pruned when the roots hit the open water or if the soil does not have adequate moisture, the roots will grow very rapidly in the water and cease growth when they encounter soil. These containers are not widely used in production nurseries due to the abundance of root rot organisms in this wet environment.
The first methods of root pruning mentioned above have been in commercial use since the first air pruning began with Dr. Carl Whitcomb's research in 1969. Refinements of these products began in the 80's and continue to this day. The first fabric container designed to be used in the ground and cause constriction pruning was done with the Root Control Bag in 1980. The first grow-bag appeared in 1983.
Newest Products
One new product, RootMaker® propagation tray is an injection-molded container of various sizes with a series of saw-tooth like ledges and openings on the sides and bottom for air-root-pruning. Seeds planted in these propagation containers develop roots in all directions, not just down.
Another effective air-root-pruning product is a line of fabric aeration containers, called Smart Pots® that use a porous black fabric to cool the soil by evaporating soil water with air movement. When this happens, salts accumulate on the container surface from both fertilizers and irrigation water. This causes the fabric containers to have a white residue develop over months or years. Even algae growth on the sides provide an added benefit for less watering and keeping the root ball cooler.
Advantages of Fibrous Root Producing Containers
With smooth-walled conventional containers, roots become concentrated and congested against the inner sidewall with little root exploration into the central volume of the container. Once that inner sidewall area is exploited, root exploration and nutrient mining is restricted and the tree begins to stagnate and decline. These new types of containers eliminate this problem.
Disadvantages
There are some disadvantages of fibrous rooting products:
- Smaller Ball Size – root pruning often produces a larger plant in a smaller than expected ball size. The American Standard for Nursery Stock is a set of standards regarding ball sizes for plants grown in fabric containers. The complete Standard is available online from American Hort. The Standard does make accommodations for fibrous root systems. However, since many more trees can be shipped on a truck compared to a typically grown B&B load, this will reduce shipping costs per tree and may not be considered a disadvantage. The standard allows parties to come to common language and relationships on the following:
- Specifying and stating the size of plants
- Relationship among caliper, height, branch number
- Size of root ball, container, or box
- Water Needs – the smaller ball size is easier to handle but they must be watered more often than B&B and they may need to be root stabilized until they have become established.
- Fabric Removal – the fabric and all containers must be removed at the time of the final installation from all trees grown in the above mentioned containers. When handled properly, fabric removal is usually easy and it must be done.
Tree Installation
Trees raised in any of the containers mentioned can be installed directly from the container. Proper tree planting techniques must be followed even with all the advantages of fibrous roots.
Conclusion
With timely air-root-pruning of seedlings and cuttings, and provisions for continued horizontal root development, trees can be consistently produced with highly efficient fibrous root systems that extend in all directions following transplanting. They establish more quickly following transplanting because they more efficiently utilize the volume of soil available with their many small roots. Trees grown this way may require root stabilizing or staking during the first growing season after final installation. The greater the support of roots for the shoots, the faster both shoots and roots grow and the healthier the tree, regardless of the soil conditions.
Washing Roots Before Installation
Many problems related to newly installed trees can be traced to root defects, poor root preparation, and poor installation practices. These factors result in circling and girdling roots, root decline, infestations by secondary pests and diseases, and early tree failure. A buried flare is also a problem that is not discovered until the tree has been dug and installed in a new location that often results in an early death of the tree.
Field applications over the past two decades have demonstrated that root washing Balled and Burlapped (B&B) and containerized trees lead to substantial increases in tree establishment and survival. The process basically changes container and B&B stock to bare root stock. The washing will expose the entire root system and reveal the flare and graft union. It allows for remediation of damaged roots and it eliminates any disparity of texture between the soils of the root ball and the installation site.
Investing the extra time to prepare and install trees properly will pay future dividends of reduced maintenance and a long life for the tree. Furthermore, the washed roots save labor during installation because the holes are shallower, less heavy equipment is required, and there are fewer worker back injuries.
The Process
In order to achieve success with the root washing process, there are 9 recommended steps to follow.
1. Remove the entire wire basket, twine, and burlap, or the container from the root ball. Do this work in a location such as a wheelbarrow, where the soil can remain or where it can easily be transported to another site.
2. Place the tree in the large container where the soil can easily be washed off or removed with fingers or small garden hand tools. Soil that is packed around the root must be washed off with a hose or raising the tree up and down in the water in the container to wash off the soil. Soaking also allows the soil to slough off gently. The duration of soaking depends on the amount of clay in the root ball and the soil compaction level.
3. Look for root defects and prune any that needs removal.
4. Dig the planting hole to be only as deep as the root system and at least three times as wide. The hole dimensions will vary depending on the size of the root system, after the soil has been removed. The hole should resemble a shallow saucer.
5. Form a soil mound in the center of the hole to support the root crown of the tree and arrange the roots radially.
6. Backfill the hole with the soil just removed from the hole, while adding water. Continue this process in lifts. Do not use any type of soil amendment unless the soil test shows deficiencies.
7. The water used for installation should preferably be from the container used to wash the soil off the roots. This water will contain the nutrients and microbes that assisted the tree's growth at the nursery. Water will settle the soil and the tree roots will hold the tree upright. If soil tests indicate a nutrient deficiency, add the appropriate fertilizer at this time. Do not add fertilizer on the bare roots, because the fertilizer will burn them. Do not step on the roots or in the root zone, not even to pack the roots down. This causes compaction to the soil. Instead, gently jiggle the tree back and forth as the water is draining. This will encourage the soil to come into contact with the roots.
8. Once the soil is added to be level with the flare, add a mechanical root stabilizer system if the tree might tip over. Then mulch the entire planting circle. The depth will vary with the mulch texture. Fine particle mulch should be 2 inches (5 cm) thick or less, while coarse mulch should be 4 inches (10 cm) thick or less. The mulch should start at least 3 inches (7.5 cm) from the trunk of the tree and extend outward to the edge of the planting pit.
9. Water the tree for the next three years adjusting the amount of the water according to the annual growth and
natural rainfall. The amount of water will vary according to the soil type and rainfall.
Limited Root Wash
Sometimes it may be easier to modify the above steps if the tree can have the soil removed right in the installation hole. In this case the tree is set near the planting site. The wire basket and twine is removed from the top of the root ball and the flare is located using fingers or water from a garden hose. The hole is dug as deep as the root system between the flare and the bottom of the root ball and three times the width. Place the tree in the hole and remove all the remaining wire and burlap or container, and soil, with garden hand tools and water. Backfill and continue the installation as mentioned above. Stabilizing and long-term watering are also the same as above.
Many problems related to newly installed trees can be traced to root defects, poor root preparation, and poor installation practices. These factors result in circling and girdling roots, root decline, infestations by secondary pests and diseases, and early tree failure. A buried flare is also a problem that is not discovered until the tree has been dug and installed in a new location that often results in an early death of the tree.
Field applications over the past two decades have demonstrated that root washing Balled and Burlapped (B&B) and containerized trees lead to substantial increases in tree establishment and survival. The process basically changes container and B&B stock to bare root stock. The washing will expose the entire root system and reveal the flare and graft union. It allows for remediation of damaged roots and it eliminates any disparity of texture between the soils of the root ball and the installation site.
Investing the extra time to prepare and install trees properly will pay future dividends of reduced maintenance and a long life for the tree. Furthermore, the washed roots save labor during installation because the holes are shallower, less heavy equipment is required, and there are fewer worker back injuries.
The Process
In order to achieve success with the root washing process, there are 9 recommended steps to follow.
1. Remove the entire wire basket, twine, and burlap, or the container from the root ball. Do this work in a location such as a wheelbarrow, where the soil can remain or where it can easily be transported to another site.
2. Place the tree in the large container where the soil can easily be washed off or removed with fingers or small garden hand tools. Soil that is packed around the root must be washed off with a hose or raising the tree up and down in the water in the container to wash off the soil. Soaking also allows the soil to slough off gently. The duration of soaking depends on the amount of clay in the root ball and the soil compaction level.
3. Look for root defects and prune any that needs removal.
4. Dig the planting hole to be only as deep as the root system and at least three times as wide. The hole dimensions will vary depending on the size of the root system, after the soil has been removed. The hole should resemble a shallow saucer.
5. Form a soil mound in the center of the hole to support the root crown of the tree and arrange the roots radially.
6. Backfill the hole with the soil just removed from the hole, while adding water. Continue this process in lifts. Do not use any type of soil amendment unless the soil test shows deficiencies.
7. The water used for installation should preferably be from the container used to wash the soil off the roots. This water will contain the nutrients and microbes that assisted the tree's growth at the nursery. Water will settle the soil and the tree roots will hold the tree upright. If soil tests indicate a nutrient deficiency, add the appropriate fertilizer at this time. Do not add fertilizer on the bare roots, because the fertilizer will burn them. Do not step on the roots or in the root zone, not even to pack the roots down. This causes compaction to the soil. Instead, gently jiggle the tree back and forth as the water is draining. This will encourage the soil to come into contact with the roots.
8. Once the soil is added to be level with the flare, add a mechanical root stabilizer system if the tree might tip over. Then mulch the entire planting circle. The depth will vary with the mulch texture. Fine particle mulch should be 2 inches (5 cm) thick or less, while coarse mulch should be 4 inches (10 cm) thick or less. The mulch should start at least 3 inches (7.5 cm) from the trunk of the tree and extend outward to the edge of the planting pit.
9. Water the tree for the next three years adjusting the amount of the water according to the annual growth and
natural rainfall. The amount of water will vary according to the soil type and rainfall.
Limited Root Wash
Sometimes it may be easier to modify the above steps if the tree can have the soil removed right in the installation hole. In this case the tree is set near the planting site. The wire basket and twine is removed from the top of the root ball and the flare is located using fingers or water from a garden hose. The hole is dug as deep as the root system between the flare and the bottom of the root ball and three times the width. Place the tree in the hole and remove all the remaining wire and burlap or container, and soil, with garden hand tools and water. Backfill and continue the installation as mentioned above. Stabilizing and long-term watering are also the same as above.
Bare Root Installation with a Pneumatic Soil-excavating Tool
Bare root (BR) transplanting with a pneumatic soil-excavating tool is actually an old method using modern tools and technology developed in the late 1990's. The pneumatic soil-excavating tool, also called Air-Spade® was introduced to the tree industry and promoted mainly to diagnose and treat root problems. The Air-Spade® is a venturi nozzled tube that attaches to an air compressor modified to generate a supersonic velocity of air to dislodge soil.
When used around trees, it can:
When the pneumatic soil-excavating tool is being used for transplanting trees BR, the soil is excavated from above and below the roots. This process allows the tree to retain up to 95% of the root mass, which results in little or no transplant shock. This technique provides the ability to transplant trees throughout the growing season (spring, summer, and autumn) with success. After using the pneumatic soil-excavating tool, the bare roots are sprayed with water and covered with wet burlap. Regardless of the weather, season, and species, most trees do not even show signs of wilt during the air tooling and moving process. Trees up to 15 inches (38 cm) DBH are easily moved with this bare root technique.
Labor costs for using the pneumatic soil-excavating tool is more than using a tree spade, but equipment costs are much less. The result is that the total cost for using the pneumatic soil-excavating tool is half the cost of moving a tree with the tree spade. Plus the tree survival rate is much higher with the pneumatic soil-excavating tool than with the tree spade and trees with up to 12 in diameter trunks are easily moved.
Steps For Moving Trees With A Pneumatic Soil-excavating Tool
Advantages
People who have used this technique are confident that bare root transplanting is perhaps the best way to relocate a tree and the pneumatic soil-excavating tool is expected to revolutionize transplanting in the future. Several tree transplanting companies are now specializing in this technique. The following articles discuss the transplanting technique at length. Bare Roots Transplanting and Taking Place in the Trees
Bare root (BR) transplanting with a pneumatic soil-excavating tool is actually an old method using modern tools and technology developed in the late 1990's. The pneumatic soil-excavating tool, also called Air-Spade® was introduced to the tree industry and promoted mainly to diagnose and treat root problems. The Air-Spade® is a venturi nozzled tube that attaches to an air compressor modified to generate a supersonic velocity of air to dislodge soil.
When used around trees, it can:
- reduce soil compaction,
- till the soil,
- reveal girdling roots,
- locate the flare,
- locate roots for utility line installation,
- investigate root damage,
- check the adequacy of the root structure,
- accurately diagnosis root diseases.
When the pneumatic soil-excavating tool is being used for transplanting trees BR, the soil is excavated from above and below the roots. This process allows the tree to retain up to 95% of the root mass, which results in little or no transplant shock. This technique provides the ability to transplant trees throughout the growing season (spring, summer, and autumn) with success. After using the pneumatic soil-excavating tool, the bare roots are sprayed with water and covered with wet burlap. Regardless of the weather, season, and species, most trees do not even show signs of wilt during the air tooling and moving process. Trees up to 15 inches (38 cm) DBH are easily moved with this bare root technique.
Labor costs for using the pneumatic soil-excavating tool is more than using a tree spade, but equipment costs are much less. The result is that the total cost for using the pneumatic soil-excavating tool is half the cost of moving a tree with the tree spade. Plus the tree survival rate is much higher with the pneumatic soil-excavating tool than with the tree spade and trees with up to 12 in diameter trunks are easily moved.
Steps For Moving Trees With A Pneumatic Soil-excavating Tool
- Hydrate the tree's roots thoroughly before excavating it. Water deeply at least 72 hours before the move.
- Start the excavation process by making a circular trench at the drip line using a small backhoe. With that completed, continue using the backhoe to excavate inward toward the trunk until roots are discovered. Then begin using the pneumatic soil-excavating tool at the trunk, by blowing soil outward and into the circular trench.
- Blow off the soil to expose the tree's roots. Keep the exposed roots as moist as possible during the digging and lifting the roots. As a section is completed, the roots are gathered and tied up in a pigtail fashion, then the pigtail is raised and tied to the tree trunk or lower branches as the roots are moistened again. The pneumatic soil-excavating tool does cause some root drying so moistening the roots is very important.
- Continue this process moving around the tree.
- Once all of the roots are exposed and tied up to the tree, the tree is ready to be moved to the new location, which has been dug the same size as the hole from which the tree is being removed. A forklift is the best machine to use for picking up and moving the tree.
- Install the tree at the same grade as it was in its original location. The new planting hole will not have to be very deep.
- Untie the roots from the pigtails and spread them out in approximately their same orientation from which they came. Moisten the roots again.
- Options at this point include adding some soil amendments like compost; a hydrogel to maintain moisture levels during the re-establishment period; and a light application of a phosphorus booster, which is a root-enhancing fertilizer that promotes root growth.
- Backfill with the soil excavated from the new location. The best way to backfill is with labor and shovels. However if equipment is used, be sure it is equipped with wide tracks or tires. Soil compaction is not acceptable after all this effort to protect and save the tree.
- Build a saucer of soil at the edge of the new installation excavation.
- Immediately after backfilling, flood the saucer area with water to eliminate air pockets, then mulch.
- Continue to irrigate the tree throughout the growing season to ensure the tree becomes established.
- Root stabilizing or staking is not necessary but may be useful at a windy site.
Advantages
- As little as 5%-15% of roots are cut, unlike the conventional methods that cuts between 50%-85% of the root mass. Most of the trees roots are moved with the tree, compared to 30% with a tree spade or 5% by B&B. This means a minimized transplant shock. The tree is also significantly lighter in weight for transporting.
- The pneumatic soil-excavating tool is considered a less expensive option to transplanting than with a tree spade.
- Without heavy soil on the roots, smaller machines are needed to lift the tree.
- The pneumatic soil-excavating tool is useful for transplanting specimen trees.
- Guying is not always required, because root stablizing is a better choice.
People who have used this technique are confident that bare root transplanting is perhaps the best way to relocate a tree and the pneumatic soil-excavating tool is expected to revolutionize transplanting in the future. Several tree transplanting companies are now specializing in this technique. The following articles discuss the transplanting technique at length. Bare Roots Transplanting and Taking Place in the Trees
Digging Trees at the Nursery
Arborists and landscape architects are often called upon to select trees from the nursery for installation in their municipality or client’s yards. Here are a few guidelines to follow.
Tree Selection
Tree selection includes choosing the appropriate species or cultivar for the installation site based on a site analysis. Then, suitable nursery stock must be chosen based on site conditions and intended after-care. The nursery stock must be inspected carefully to pick the best quality trees. Trees of poor quality may be inexpensive in some cases but they will also perform poorly in the landscape. To ensure greater transplant survival it is essential to choose trees grown in a nursery production system best suited for the planting site. Also be sure the first major root is within 1" (2 cm) of the top of the root ball.
Digging the Tree
Digging the trees is the responsibility of the nursery; however, the arborist or landscape architect should be aware of the latest edition of the American Standard for Nursery Stock: American Association of Nurserymen, to obtain the correct sizes. If the trees are dug in the wild or are a species known to have difficulty transplanting, the root ball should be the next larger size indicated on the standard. Bare root trees should be dug with as many roots as possible and immediately cleaned and put into storage.
Root Losses
The percentage of the root system is harvested depending on what question is asked. There are several ways to express the percentage of the root system lost when field-grown trees are dug B&B from a nursery:
Bare root trees generally have 80% to 95% of their roots dug and kept on the tree throughout the installation process.
Root pruning a year before harvesting increases the amount of new roots in the root ball. This is why survival of previously root pruned trees after transplanting is so much greater than on trees that were not root pruned.
Transporting Trees
Tree roots are fragile and should be handled carefully. Since picking the tree up by the trunk could strip the bark, lift and carry the tree by the bottom of the root ball if possible. Never drop the tree because this will break roots and disrupt contact between the fine roots and soil, often resulting in death of the tree.
Some nurseries shrink-wrap black plastic around the outside of the root ball to help hold the ball together and reduce water loss from the tree and roots during transport to the planting site. If the trees cannot be installed immediately, clear plastic-wrapped trees should be kept in the shade or covered if the sun will cause temperatures to reach stressful levels of over 86° F (30° C).
Tie trees securely to the transport truck so that they do not roll around during transport; rolling can crack the root ball and break the roots. Branches normally are tied together close to the trunk for the same reason. Bare root trees should have their roots be completely covered and moist at all times during the transport. Be sure all trees are irrigated prior to shipping in order to minimize desiccation.
When the trees arrive on the site, they should be inspected for damage. The roots should be inspected to be sure that they are sufficiently moist. Any tree with dry roots should be rejected along with trees that are severely damaged. Depth to the flare should be less than 2 inches (5 cm.) from the surface of the root ball.
Arborists and landscape architects are often called upon to select trees from the nursery for installation in their municipality or client’s yards. Here are a few guidelines to follow.
Tree Selection
Tree selection includes choosing the appropriate species or cultivar for the installation site based on a site analysis. Then, suitable nursery stock must be chosen based on site conditions and intended after-care. The nursery stock must be inspected carefully to pick the best quality trees. Trees of poor quality may be inexpensive in some cases but they will also perform poorly in the landscape. To ensure greater transplant survival it is essential to choose trees grown in a nursery production system best suited for the planting site. Also be sure the first major root is within 1" (2 cm) of the top of the root ball.
Digging the Tree
Digging the trees is the responsibility of the nursery; however, the arborist or landscape architect should be aware of the latest edition of the American Standard for Nursery Stock: American Association of Nurserymen, to obtain the correct sizes. If the trees are dug in the wild or are a species known to have difficulty transplanting, the root ball should be the next larger size indicated on the standard. Bare root trees should be dug with as many roots as possible and immediately cleaned and put into storage.
Root Losses
The percentage of the root system is harvested depending on what question is asked. There are several ways to express the percentage of the root system lost when field-grown trees are dug B&B from a nursery:
- Calculate the soil volume in a typical root ball and compare this to the total theoretical root system volume on the entire tree. Researchers have found that from 2% to 5% of the total root volume is usually harvested with the B&B tree.
- Measure root length harvested in the root ball compared with the amount left behind in the nursery. Researchers have found that only 5% to 8% of the root system length is usually harvested.
- Measure the surface area of the roots in the root ball compared to the surface area left behind in the nursery. Researchers have found that 55% to 60% of the root surface area was harvested.
- Weigh the roots. Researchers have found that up to 82% of the root weight was harvested with a typical B&B root ball.
Bare root trees generally have 80% to 95% of their roots dug and kept on the tree throughout the installation process.
Root pruning a year before harvesting increases the amount of new roots in the root ball. This is why survival of previously root pruned trees after transplanting is so much greater than on trees that were not root pruned.
Transporting Trees
Tree roots are fragile and should be handled carefully. Since picking the tree up by the trunk could strip the bark, lift and carry the tree by the bottom of the root ball if possible. Never drop the tree because this will break roots and disrupt contact between the fine roots and soil, often resulting in death of the tree.
Some nurseries shrink-wrap black plastic around the outside of the root ball to help hold the ball together and reduce water loss from the tree and roots during transport to the planting site. If the trees cannot be installed immediately, clear plastic-wrapped trees should be kept in the shade or covered if the sun will cause temperatures to reach stressful levels of over 86° F (30° C).
Tie trees securely to the transport truck so that they do not roll around during transport; rolling can crack the root ball and break the roots. Branches normally are tied together close to the trunk for the same reason. Bare root trees should have their roots be completely covered and moist at all times during the transport. Be sure all trees are irrigated prior to shipping in order to minimize desiccation.
When the trees arrive on the site, they should be inspected for damage. The roots should be inspected to be sure that they are sufficiently moist. Any tree with dry roots should be rejected along with trees that are severely damaged. Depth to the flare should be less than 2 inches (5 cm.) from the surface of the root ball.
The Missouri Gravel Bed
The Missouri Gravel Bed (MGB) is a user-friendly method of handling bare root (BR) nursery stock into which dormant trees are placed in the spring with their bare roots in an irrigated bed of pea gravel and held for up to 6 months before planting BR (even in full leaf) into the landscape. It is not a growing method, but can be used by growers, retail and landscape nurseries, arborists, landscape architects and city foresters to extend the planting season and to greatly simplify the handling of BR stock. It also shows promise as a method for heeling in B&B stock. The key to MGB is that root growth in pea gravel is very fibrous and, unlike mulch or sand, very few roots are damaged when trees are pulled from the gravel.
There is nothing high tech about MGB. All that is required is a layer of pea gravel deep enough to cover the roots and a timer controlled irrigation system. Trees are simply placed with their roots in the gravel in spring and allowed to develop roots in the rock until the time to plant in soil or permanent location. A surface application of slow release fertilizer has proven effective in keeping the trees green. Under MGB conditions, a drip system is designed to come on for 3 minutes every 4 hours between 10 AM and 6 PM even during hot and dry periods. Once the growth flush has hardened a bit, the watering frequency can be cut back to perhaps 3 minutes three times a day. The irrigation controller should, of course, be adjusted occasionally based on weather and tree appearance. Recent research has shown that, when calcined clay (Turface or TerraGreen) is incorporated, beds can be irrigated once every day or two with excellent results.
Development
The MGB was developed at the University of Missouri Horticulture Research Center in 1985. In the initial test, twenty 4 – 6 feet (1.2 –1.8m) BR Washington hawthorn trees spent 8 weeks with their roots in aerated water. Then they were field installed in mid-summer and they all survived. While aerated water grows good roots, it does not provide any support, creating problems in tree handling. Because of this, MGB since 1986 have used irrigated, creek gravel as a medium for growing fibrous roots while being held before final installation.
Over the past 20 years, many species have been tested in MGBs including ornamental pears, redbuds, flowering dogwood, lindens, maples, crabapples, and roses. A test in 1994 at Sherman Nursery and Sjulin Nursery, both in Iowa, evaluated the performance of 130 species of trees and shrubs, reporting no injury to roots of trees left in the pea gravel during a winter down to -25°F (-32°C). Overall, the survival of MGB trees has been as good as or better than that expected for container grown or B&B materials. In one study, 2 inch (5cm) caliper ash trees showed 100% survival when field installed BR in full leaf in July from a gravel bed. In a recent test, trees up to 5 inch (12cm) caliper survived and showed no wilting after a BR installation in late July after 20 weeks in a gravel bed.
How It Works
Retail customers may be hesitant at first to buy trees with their roots right out in the open. However, the main reason why MGB works so well is that actively growing roots are placed in direct contact with the soil in which they will grow in the landscape without the interface problems that can happen with container and B&B stock. When trees are removed from the pea gravel, spraying the roots with water and putting them in a plastic bag is sufficient if the trees will be installed within a day or two (assuming they are not left in the SUV or pickup truck at the Mall parking lot). If the top growth is very soft, it may be advisable to wrap whole trees or bundles of trees in a sheet of plastic. Five or six times as many MGB trees will fit in a car as container trees of the same size. A bucket of water poured in the hole at planting time is often the only care required once the trees are in the ground.
Pros
Advantages of handling BR trees in MGB rather than container grown or B&B include:
Construction and Management of MGB
Using the typical design for MGB, a mixture of pea gravel 0.4 inches (10 mm) in diameter and 10% to 15% fine sand is placed on polyethylene film, broadcast with granular, slow release fertilizer and drip irrigated 3 to 4 times per day. Railroad ties or dimension lumber can be used around the edge to make the bed look tidy. A drip irrigation system works well, with lines spaced 1 foot (30cm) apart and running the length of the bed from a header across the bed width. Emitters (1 gph) are spaced at 12 inches (30cm) in the line. Irrigation lines can then be pressurized by a sump pump and activated by a time clock. If using this approach, be sure to run a water supply line to the sump with a float valve to replenish water lost to evaporation and transpiration. Recent results indicate that incorporating 20% to 40% calcined clay into the gravel, without sand, improves tree growth and eliminates the need to recycle the irrigation water.
Bed Management
Trees are placed in the bed by digging a trench in the pea gravel and then shoveling gravel back over the roots. It is helpful to wet the gravel before making the trench. Spacing of trees in the bed will depend on tree size. Staggered rows work well for trees 6' – 8' (1.8 – 2.4cm) tall as close as 16 inches (40cm) apart in the row. Up to 100 trees can be placed in a 100 square foot (9.5 sq. meters) module including trees and shrubs. It is best to get the bed set up early to allow for good root development before the onset of hot temperatures. Until trees leaf out, watering is not critical. Water the trees in well by hand and then set the time clock to water once a day for about 5 minutes. When the trees have begun to leaf out, set the time clock to irrigate about 3 or 4 minutes every 4 hours during the daylight hours. Later, when the growth has slowed, the irrigation frequency can be reduced to once or twice per day. Let the trees be your guide. As noted previously, incorporating calcined clay into the gravel greatly reduces the irrigation frequency required to keep trees in good condition.
Slow release fertilizer granules applied to the surface of the pea gravel will keep the trees green. A material that contains sulfur will help counteract the effects of irrigating with alkaline water. Use a rate similar to that for topdressing container stock but apply 3 times at monthly intervals.
When removing trees from the gravel, lay the trees on a piece of plastic and spray them with water. A bundle of five or ten trees can be wrapped up and tied with twine. If the bundle is not opened and is kept in a cool place, the trees can be kept for several days before installation. Dipping the roots in hydrogel does not seem to provide any real benefit and may actually interfere with root growth in some cases. It is best to just check occasionally and spray the roots with water if they begin to dry out. Later in the season, after the top growth has hardened, the roots can be placed in a large plastic bag and the tops left exposed.
When planting, the only critical thing is that a few gallons of water be added to the planting hole immediately after installation. This is often the only care required, as the roots can begin taking up water from the backfill soil immediately and are not subject to drought stress due to drying of a soil ball.
Uses for the MGB
The Missouri Gravel Bed (MGB) is a user-friendly method of handling bare root (BR) nursery stock into which dormant trees are placed in the spring with their bare roots in an irrigated bed of pea gravel and held for up to 6 months before planting BR (even in full leaf) into the landscape. It is not a growing method, but can be used by growers, retail and landscape nurseries, arborists, landscape architects and city foresters to extend the planting season and to greatly simplify the handling of BR stock. It also shows promise as a method for heeling in B&B stock. The key to MGB is that root growth in pea gravel is very fibrous and, unlike mulch or sand, very few roots are damaged when trees are pulled from the gravel.
There is nothing high tech about MGB. All that is required is a layer of pea gravel deep enough to cover the roots and a timer controlled irrigation system. Trees are simply placed with their roots in the gravel in spring and allowed to develop roots in the rock until the time to plant in soil or permanent location. A surface application of slow release fertilizer has proven effective in keeping the trees green. Under MGB conditions, a drip system is designed to come on for 3 minutes every 4 hours between 10 AM and 6 PM even during hot and dry periods. Once the growth flush has hardened a bit, the watering frequency can be cut back to perhaps 3 minutes three times a day. The irrigation controller should, of course, be adjusted occasionally based on weather and tree appearance. Recent research has shown that, when calcined clay (Turface or TerraGreen) is incorporated, beds can be irrigated once every day or two with excellent results.
Development
The MGB was developed at the University of Missouri Horticulture Research Center in 1985. In the initial test, twenty 4 – 6 feet (1.2 –1.8m) BR Washington hawthorn trees spent 8 weeks with their roots in aerated water. Then they were field installed in mid-summer and they all survived. While aerated water grows good roots, it does not provide any support, creating problems in tree handling. Because of this, MGB since 1986 have used irrigated, creek gravel as a medium for growing fibrous roots while being held before final installation.
Over the past 20 years, many species have been tested in MGBs including ornamental pears, redbuds, flowering dogwood, lindens, maples, crabapples, and roses. A test in 1994 at Sherman Nursery and Sjulin Nursery, both in Iowa, evaluated the performance of 130 species of trees and shrubs, reporting no injury to roots of trees left in the pea gravel during a winter down to -25°F (-32°C). Overall, the survival of MGB trees has been as good as or better than that expected for container grown or B&B materials. In one study, 2 inch (5cm) caliper ash trees showed 100% survival when field installed BR in full leaf in July from a gravel bed. In a recent test, trees up to 5 inch (12cm) caliper survived and showed no wilting after a BR installation in late July after 20 weeks in a gravel bed.
How It Works
Retail customers may be hesitant at first to buy trees with their roots right out in the open. However, the main reason why MGB works so well is that actively growing roots are placed in direct contact with the soil in which they will grow in the landscape without the interface problems that can happen with container and B&B stock. When trees are removed from the pea gravel, spraying the roots with water and putting them in a plastic bag is sufficient if the trees will be installed within a day or two (assuming they are not left in the SUV or pickup truck at the Mall parking lot). If the top growth is very soft, it may be advisable to wrap whole trees or bundles of trees in a sheet of plastic. Five or six times as many MGB trees will fit in a car as container trees of the same size. A bucket of water poured in the hole at planting time is often the only care required once the trees are in the ground.
Pros
Advantages of handling BR trees in MGB rather than container grown or B&B include:
- reduced tree maintenance, harvesting, and shipping costs,
- ability to harvest a larger root system means an excellent survival rate,
- lower costs for the lack of containers and potting soil,
- trees are lighter and easier to handle than container grown or B&B trees of the same size,
- reduced equipment needs for handling,
- MGB is easy to install and lasts for many years.
Construction and Management of MGB
Using the typical design for MGB, a mixture of pea gravel 0.4 inches (10 mm) in diameter and 10% to 15% fine sand is placed on polyethylene film, broadcast with granular, slow release fertilizer and drip irrigated 3 to 4 times per day. Railroad ties or dimension lumber can be used around the edge to make the bed look tidy. A drip irrigation system works well, with lines spaced 1 foot (30cm) apart and running the length of the bed from a header across the bed width. Emitters (1 gph) are spaced at 12 inches (30cm) in the line. Irrigation lines can then be pressurized by a sump pump and activated by a time clock. If using this approach, be sure to run a water supply line to the sump with a float valve to replenish water lost to evaporation and transpiration. Recent results indicate that incorporating 20% to 40% calcined clay into the gravel, without sand, improves tree growth and eliminates the need to recycle the irrigation water.
Bed Management
Trees are placed in the bed by digging a trench in the pea gravel and then shoveling gravel back over the roots. It is helpful to wet the gravel before making the trench. Spacing of trees in the bed will depend on tree size. Staggered rows work well for trees 6' – 8' (1.8 – 2.4cm) tall as close as 16 inches (40cm) apart in the row. Up to 100 trees can be placed in a 100 square foot (9.5 sq. meters) module including trees and shrubs. It is best to get the bed set up early to allow for good root development before the onset of hot temperatures. Until trees leaf out, watering is not critical. Water the trees in well by hand and then set the time clock to water once a day for about 5 minutes. When the trees have begun to leaf out, set the time clock to irrigate about 3 or 4 minutes every 4 hours during the daylight hours. Later, when the growth has slowed, the irrigation frequency can be reduced to once or twice per day. Let the trees be your guide. As noted previously, incorporating calcined clay into the gravel greatly reduces the irrigation frequency required to keep trees in good condition.
Slow release fertilizer granules applied to the surface of the pea gravel will keep the trees green. A material that contains sulfur will help counteract the effects of irrigating with alkaline water. Use a rate similar to that for topdressing container stock but apply 3 times at monthly intervals.
When removing trees from the gravel, lay the trees on a piece of plastic and spray them with water. A bundle of five or ten trees can be wrapped up and tied with twine. If the bundle is not opened and is kept in a cool place, the trees can be kept for several days before installation. Dipping the roots in hydrogel does not seem to provide any real benefit and may actually interfere with root growth in some cases. It is best to just check occasionally and spray the roots with water if they begin to dry out. Later in the season, after the top growth has hardened, the roots can be placed in a large plastic bag and the tops left exposed.
When planting, the only critical thing is that a few gallons of water be added to the planting hole immediately after installation. This is often the only care required, as the roots can begin taking up water from the backfill soil immediately and are not subject to drought stress due to drying of a soil ball.
Uses for the MGB
- This system has been designed mostly for retail nursery use. Unfortunately, the little community garden centers that could use this system are rare.
- The MGB is currently being tested by city parks and urban forestry professionals as a tool to reduce costs and improve survival in BR tree installation programs. For cities planning major bare root installation programs with volunteers, they could use the gravel bed system for the exceptions rather than carrying the main weight of the program. MGB is a natural extension of the methods for BR tree installation developed by Dr. Nina Bassuk in Ithaca, NY. Dr. Bassuk has shown that BR street trees installed while still dormant, perform as well as or better than balled and burlapped trees of the same size. MGB takes advantage of the lower cost and lighter weight of BR stock without being restricted to installing during the dormant season.
- Design/build landscapers should consider the MGB as the best practical applications for them to use. It would allow long season bare root installation, and the landscaper would have a great deal of control over the trees.
A Tree Planting Program that Works
In Wellesley, Massachusetts, the Park and Highway Division within the Public Works Department has the responsibility for installing new trees. Most of these new trees are installed on private property with public funds. State law allows communities to install public trees between the sidewalk and 20 feet from the edge of the public way and Wellesley has adopted this as a policy. This setback practice results in healthier trees that grow better, faster, and live longer than trees installed next to the street curb. These trees receive less damage from exhaust fumes, road salt, and car doors; their lower branches do not get hit by tall trucks; their upper branches do not grow into the utility wires; and their roots have plenty of good soil to grow in.
Throughout most of the 1990's, Wellesley set aside $25,000 each year for the installation of new trees. These funds were sufficient for installing an average of 300 trees. (Note: This article is a reprint that appeared in Online Seminar #7, May/April 2006, so the prices in this paragraph are not valid today but the rest of the article is accurate.)
Tree Selection
The program placed a great emphasis on selecting and installing trees bare root. The costs were significantly less not only for the cost of purchasing the tree, but also for the cost of contracted labor to do the actual installation.
The program begins in the autumn prior to the spring installation. The municipal arborist prepares a list of trees to be considered for the next season. The list contains a 50 - 50 mix of flowering trees, columnar trees and shade trees with one evergreen species. Half the trees mature at a large size and the other half stay under 25 feet in height, for installing in combination with large trees or on the side of the street where overhead wires could be a potential problem. The columnar trees are installed on the overhead wires side of the street but far enough from the wires to become a problem.
All the trees that are selected for installation each year are species known to do well in the urban Massachusetts environment. Also selected are new cultivars that have been bred to tolerate city conditions. The trees selected do not require very much maintenance; they are pest and disease resistant; the soils are matched to tree preference which allows the roots to grow with a minimum of effort; and the trees are cold and heat resistant to ensure survival.
Obtaining Quotes
Once a plant list is prepared; it is sent to 6 – 8 nurseries known to offer high quality trees, to obtain availability and pricing information for delivery the following spring. All the trees are to be quoted at 2" diameter or less and bare root, if possible. A minimum quantity of 10 trees is requested to take advantage of quantity discounts. Substitution of size and species or cultivar is allowed at this time only. The nurseries respond with what they can offer. Using this information, the list is revised according to size, price, species, and quantity of available trees. The revised list is sent back to the nurseries for a final quote. Generally, 3 - 4 nurseries are selected for specific trees. Upon return of the quotes, purchase orders are placed with each nursery. Since so many nurseries are involved, none of the orders exceed the $10,000 threshold above which the state requires competitive bidding. Therefore, the timely and expensive bidding process is avoided.
The same process is undertaken for selecting tree-planting contractors. At least 6 – 7 contractors known to be skilled and knowledgeable in installation techniques for bare root trees are sent quote sheets for installing a given number of trees at each of the sizes indicated on the list of trees selected. The contractors are asked to provide a unit price for each size tree. Again, because of the number of contractors and low costs per tree size, none of the contractors exceed the bid limit. In situations where the contractors quote the same price on the same size tree, both are awarded the contract and they split the number of plantings.
With this process completed in the autumn, the budget is set and the orders placed long before the spring rush, avoiding problems and disappointment with orders that are incomplete or not as desired.
Bidding versus Quotes
On average, in the 1990's, the $25,000 budget would purchase 300 trees. The average quoted cost of $53 for each tree plus the average quoted cost of $30 to install, which totals $83 per average bare root tree. (The one year that bidding was used, only 75 trees could be purchased for the $25,000. The vendors doing the bidding required a fee for program management; they specified expensive B&B trees, 2" diameter minimum size, and union labor contractors to do the installation. Less than ten trees of each species or cultivar were ordered. The average cost per tree in the ground was $333.)
The Wellesley finance director decided that obtaining quotes to purchase different tree species or cultivars as separate items and the installation of different size trees as separate items, rather than bidding the entire package did not violate the bidding laws. He was convinced of this once he saw how the available dollars installed so many more trees by competitive quote, than the bidding process would allow.
Planting Plans
Since these trees are installed on private property, the Park and Highway Division cooperates with the homeowner to be sure the trees are installed in the right place. They also believe the homeowner should have a choice of what tree is installed in their yard, so they will develop pride in the tree and feel a part of the entire tree installation program. For the funds available, as many as 30 different tree species are ordered. This gives the resident a wide variety of trees from which to select the tree they want in their yard. The program was developed with resident participation as a central goal, along with assurance that the investment in trees would not be wasted. Any left over trees were planted on public properties such as the parks, schools, conservation areas, and public buildings.
The Process
The program starts with a list of residents who have heard about the program and would like trees installed on their property. The residents on this waiting list get the first choice of trees each year. The second level of priority occurs along selected streets. Each year the Tree Advisory Committee sets a priority of streets that should get new trees. These streets are then given to the Park and Highway Division who conducts an inventory of the existing trees and selects locations where trees could possibly be installed. The Division prepares planting plans to indicate the potential installation sites.
Once the waiting list is finalized and the planting plans are accepted by the Tree Advisory Committee, the arborist contacts each homeowner to see if they are interested in having a tree installed in their front yard. If they are, the arborist makes an appointment to visit with them a couple of months prior to the installation and works with the owners regarding tree selection and the front yard location for each new tree. The arborist brings a book of photographs and descriptions of each of the trees that will be available. This information helps the owner select trees for their yard that they may not be familiar with. The locations are marked on the lawn with stakes or spray paint. The locations and species are also noted on the street tree plan.
Installation
When this process is complete, utilities are marked, and the trees are delivered to the central maintenance yard where they are stored in wood chip mulch and kept watered in a manner similar to the Missouri Gravel Bed program described above. When weather conditions are right, the installation contractors are notified to begin. Each day they take only those bare root trees needed for the day and plant their trees according to the planting plans. Close supervision is essential to be sure the trees are installed correctly. The arborist tells the contractors that “for every 30 seconds the tree's roots are exposed to sun and wind, the life of the tree is cut in half”. While this is not quite true, it insures prompt attention by the contractor when making delivery of the trees to the site as well as during the installation process. The tree roots are kept covered with wood chips or wet canvas on the delivery trucks, covered while the holes are being dug, and watered during and immediately after installation. Once the installation is completed, the trees are mulched, and a few days later the final inspection is made by the arborist. At this inspection, the homeowner is given a letter with the name of the tree and a description of the care the tree should receive.
The installation practice follows the most recent recommendations for tree installation techniques. All trees are maintained primarily with watering for two years (by the owner), pruning at installation time to remove only dead or diseased branches and three years later for structural pruning by the arborist, and an optional fertilizer treatment after the roots are established. Wellesley's research has shown that the tree survival rate is 98% after one year and 95% after 5 years. Survival after five years is nearly 100% until the trees have reached maturity. Tree removal records indicate that most of the trees on private property survive for 75 – 100 years while those next to the street survive only 40 years on average.
Program Summary
The major drawback to this program is that it requires the arborist to spend a considerable amount of time. The chart below illustrates the average amount of time necessary for the installation of 300 trees.
Tree Installation Program Time Requirements
Item Average Labor Hours
Prepare tree planting list 6
Obtain quotes 9
Prepare Purchase Orders 2
Prepare pages of descriptions 5
Prepare & check proposed plans 6
Phone for appointments 40
Attend appointments 104
Records & plans update 40
Mark & remark planting sites 20
Call Dig Safe - utility marking 2
Supervise tree installation 71
Close out 8
Total labor hours 313
Total # of trees installed 302
Budget $25,000
All of this effort indicates Wellesley's commitment to its trees, its environment, and to improving the urban landscape within the community. In fact, the program is so popular with Wellesley residents that the Finance Committee continually asks the Park and Highway Division to accept more than the $25,000 each year, so more trees can be installed. However, the gesture is declined, because the arborist does not have the time to install more trees. How many other municipal departments can make this statement?
Notes
Note: The mention of product names throughout this entire topic does not constitute an endorsement of these products. They are mentioned only for providing the reader with useful information.
Sources
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In Wellesley, Massachusetts, the Park and Highway Division within the Public Works Department has the responsibility for installing new trees. Most of these new trees are installed on private property with public funds. State law allows communities to install public trees between the sidewalk and 20 feet from the edge of the public way and Wellesley has adopted this as a policy. This setback practice results in healthier trees that grow better, faster, and live longer than trees installed next to the street curb. These trees receive less damage from exhaust fumes, road salt, and car doors; their lower branches do not get hit by tall trucks; their upper branches do not grow into the utility wires; and their roots have plenty of good soil to grow in.
Throughout most of the 1990's, Wellesley set aside $25,000 each year for the installation of new trees. These funds were sufficient for installing an average of 300 trees. (Note: This article is a reprint that appeared in Online Seminar #7, May/April 2006, so the prices in this paragraph are not valid today but the rest of the article is accurate.)
Tree Selection
The program placed a great emphasis on selecting and installing trees bare root. The costs were significantly less not only for the cost of purchasing the tree, but also for the cost of contracted labor to do the actual installation.
The program begins in the autumn prior to the spring installation. The municipal arborist prepares a list of trees to be considered for the next season. The list contains a 50 - 50 mix of flowering trees, columnar trees and shade trees with one evergreen species. Half the trees mature at a large size and the other half stay under 25 feet in height, for installing in combination with large trees or on the side of the street where overhead wires could be a potential problem. The columnar trees are installed on the overhead wires side of the street but far enough from the wires to become a problem.
All the trees that are selected for installation each year are species known to do well in the urban Massachusetts environment. Also selected are new cultivars that have been bred to tolerate city conditions. The trees selected do not require very much maintenance; they are pest and disease resistant; the soils are matched to tree preference which allows the roots to grow with a minimum of effort; and the trees are cold and heat resistant to ensure survival.
Obtaining Quotes
Once a plant list is prepared; it is sent to 6 – 8 nurseries known to offer high quality trees, to obtain availability and pricing information for delivery the following spring. All the trees are to be quoted at 2" diameter or less and bare root, if possible. A minimum quantity of 10 trees is requested to take advantage of quantity discounts. Substitution of size and species or cultivar is allowed at this time only. The nurseries respond with what they can offer. Using this information, the list is revised according to size, price, species, and quantity of available trees. The revised list is sent back to the nurseries for a final quote. Generally, 3 - 4 nurseries are selected for specific trees. Upon return of the quotes, purchase orders are placed with each nursery. Since so many nurseries are involved, none of the orders exceed the $10,000 threshold above which the state requires competitive bidding. Therefore, the timely and expensive bidding process is avoided.
The same process is undertaken for selecting tree-planting contractors. At least 6 – 7 contractors known to be skilled and knowledgeable in installation techniques for bare root trees are sent quote sheets for installing a given number of trees at each of the sizes indicated on the list of trees selected. The contractors are asked to provide a unit price for each size tree. Again, because of the number of contractors and low costs per tree size, none of the contractors exceed the bid limit. In situations where the contractors quote the same price on the same size tree, both are awarded the contract and they split the number of plantings.
With this process completed in the autumn, the budget is set and the orders placed long before the spring rush, avoiding problems and disappointment with orders that are incomplete or not as desired.
Bidding versus Quotes
On average, in the 1990's, the $25,000 budget would purchase 300 trees. The average quoted cost of $53 for each tree plus the average quoted cost of $30 to install, which totals $83 per average bare root tree. (The one year that bidding was used, only 75 trees could be purchased for the $25,000. The vendors doing the bidding required a fee for program management; they specified expensive B&B trees, 2" diameter minimum size, and union labor contractors to do the installation. Less than ten trees of each species or cultivar were ordered. The average cost per tree in the ground was $333.)
The Wellesley finance director decided that obtaining quotes to purchase different tree species or cultivars as separate items and the installation of different size trees as separate items, rather than bidding the entire package did not violate the bidding laws. He was convinced of this once he saw how the available dollars installed so many more trees by competitive quote, than the bidding process would allow.
Planting Plans
Since these trees are installed on private property, the Park and Highway Division cooperates with the homeowner to be sure the trees are installed in the right place. They also believe the homeowner should have a choice of what tree is installed in their yard, so they will develop pride in the tree and feel a part of the entire tree installation program. For the funds available, as many as 30 different tree species are ordered. This gives the resident a wide variety of trees from which to select the tree they want in their yard. The program was developed with resident participation as a central goal, along with assurance that the investment in trees would not be wasted. Any left over trees were planted on public properties such as the parks, schools, conservation areas, and public buildings.
The Process
The program starts with a list of residents who have heard about the program and would like trees installed on their property. The residents on this waiting list get the first choice of trees each year. The second level of priority occurs along selected streets. Each year the Tree Advisory Committee sets a priority of streets that should get new trees. These streets are then given to the Park and Highway Division who conducts an inventory of the existing trees and selects locations where trees could possibly be installed. The Division prepares planting plans to indicate the potential installation sites.
Once the waiting list is finalized and the planting plans are accepted by the Tree Advisory Committee, the arborist contacts each homeowner to see if they are interested in having a tree installed in their front yard. If they are, the arborist makes an appointment to visit with them a couple of months prior to the installation and works with the owners regarding tree selection and the front yard location for each new tree. The arborist brings a book of photographs and descriptions of each of the trees that will be available. This information helps the owner select trees for their yard that they may not be familiar with. The locations are marked on the lawn with stakes or spray paint. The locations and species are also noted on the street tree plan.
Installation
When this process is complete, utilities are marked, and the trees are delivered to the central maintenance yard where they are stored in wood chip mulch and kept watered in a manner similar to the Missouri Gravel Bed program described above. When weather conditions are right, the installation contractors are notified to begin. Each day they take only those bare root trees needed for the day and plant their trees according to the planting plans. Close supervision is essential to be sure the trees are installed correctly. The arborist tells the contractors that “for every 30 seconds the tree's roots are exposed to sun and wind, the life of the tree is cut in half”. While this is not quite true, it insures prompt attention by the contractor when making delivery of the trees to the site as well as during the installation process. The tree roots are kept covered with wood chips or wet canvas on the delivery trucks, covered while the holes are being dug, and watered during and immediately after installation. Once the installation is completed, the trees are mulched, and a few days later the final inspection is made by the arborist. At this inspection, the homeowner is given a letter with the name of the tree and a description of the care the tree should receive.
The installation practice follows the most recent recommendations for tree installation techniques. All trees are maintained primarily with watering for two years (by the owner), pruning at installation time to remove only dead or diseased branches and three years later for structural pruning by the arborist, and an optional fertilizer treatment after the roots are established. Wellesley's research has shown that the tree survival rate is 98% after one year and 95% after 5 years. Survival after five years is nearly 100% until the trees have reached maturity. Tree removal records indicate that most of the trees on private property survive for 75 – 100 years while those next to the street survive only 40 years on average.
Program Summary
The major drawback to this program is that it requires the arborist to spend a considerable amount of time. The chart below illustrates the average amount of time necessary for the installation of 300 trees.
Tree Installation Program Time Requirements
Item Average Labor Hours
Prepare tree planting list 6
Obtain quotes 9
Prepare Purchase Orders 2
Prepare pages of descriptions 5
Prepare & check proposed plans 6
Phone for appointments 40
Attend appointments 104
Records & plans update 40
Mark & remark planting sites 20
Call Dig Safe - utility marking 2
Supervise tree installation 71
Close out 8
Total labor hours 313
Total # of trees installed 302
Budget $25,000
All of this effort indicates Wellesley's commitment to its trees, its environment, and to improving the urban landscape within the community. In fact, the program is so popular with Wellesley residents that the Finance Committee continually asks the Park and Highway Division to accept more than the $25,000 each year, so more trees can be installed. However, the gesture is declined, because the arborist does not have the time to install more trees. How many other municipal departments can make this statement?
Notes
- The planting list should vary every year to maintain proper diversification,
- Tree descriptions presented to homeowners should have colored photos of all the trees being offered,
- After each tree selection, notes should be made on the plan and on a separate list to keep track of the number of trees and their location,
- Each appointment averages ½ hour plus travel time in the beginning of the season, and ½ hour including travel time by the end of the season when there are fewer pre-ordered trees to describe,
- If locations are marked with spray paint, they have to be remarked every 2 – 3 weeks. Stakes last many more weeks but cannot be used if the ground is frozen when the tree selection is made,
- All contractors should be supervised to be sure they are installing the trees correctly, to be sure the trees are in the right location, to make adjustments to the planting locations if needed, and to answer any questions they may have,
- Close-out includes getting all the bills paid and preparing a route map so all trees can be efficiently checked periodically during the summer months,
- The number of trees installed each year varies depending on the tree sizes and associated costs.
Note: The mention of product names throughout this entire topic does not constitute an endorsement of these products. They are mentioned only for providing the reader with useful information.
Sources
- Personal communications with Gay Hinton, Carl Whitcomb, Kurt Reiger/Owner High
Caliper, and with Vincent Cotrone.
- A Bare Root Tree Planting Program that Saves Money", Urban Forestry News, Vol. 15, Issue 4, 2008.
- Bassuk, Nina, "Creating the urban forest: the bare root method”, Ithaca, NY, 2000.
- Christman, Laura, “Bare essentials: 6 tips for growing bare root trees”, The Redding Searchlight, Redding, CA January 9, 2010.
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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
*Members of ISA may apply the 4.0 CEUs toward Certified Arborist, Tree Worker Specialist, Municipal Specialist, Aerial Lift Specialist, or BCMA science credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA and MTOA members may submit your ISA certification record to these organizations and receive credits one for one.
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