EFFECTS OF ROOT AND STEM PRUNING NEWLY PLANTED AND LARGE TREES ON DECAY, ROOT REGENERATION, AND STABILITY

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0217119
• Project Start Date: Oct 1, 2008
• Project End Date: Sep 30, 2011
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611

Performing Department
ENVIRONMENTAL HORTICULTURE

Non Technical Summary
Parts one and two of this study will help us understand what root defects are important enough to treat at planting and how to treat them, and determine influence of treatment on stability. We will also have a good understanding of the influence of pruning roots of different diameters on root decay and capacity to generate new roots from the cut surface. This will provide arborists with guidelines for preventing and treating stem girdling roots and managing large trees with severed root systems. The third part of this study will contribute to the discussion of wind and trees by evaluating tree response to wind loading. This will be instructive because pruning is a practice that can acutely affect the mechanics of a tree by reducing the lever arm, sail area, and drag of the canopy. Pruning is arguably the most common cultural treatment applied to urban trees and it is likely that it has an enormous affect on the dynamics of tree growth and development. As such, it should be used judiciously and this can only be accomplished with empirical data that support appropriate practices. Removing roots that grow around the trunk from either planting too deeply, growing in a container in the nursery, cutting roots during field production, or misapplying mulch during landscape maintenance is becoming more common place in arboriculture practice. Some contractors prune roots at planting to help reduce occurrence of potential stem girdling roots, and arborists cut roots to 4" diameter and even larger on established trees as part of remediation treatments. However, there is little research to help guide these treatments. This study will evaluate root pruning techniques on tree stability and decay following root pruning newly planted and medium aged 30" dbh trees. Following this project we will have some understanding of the advantages and disadvantages of root pruning shade trees. The results will help refine the A-300 root management standard and professional practices. The discussion regarding root pruning as a means to improve plant health and reduce storm impacts on trees longs for quantitative data. This project allows us a means to take advantage of a unique opportunity with cooperating engineering faculty.

Animal Health Component

(N/A)

Research Effort Categories

Basic

100%

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
124	2110	1060	100%

Knowledge Area
124 - Urban Forestry;

Subject Of Investigation
2110 - Ornamental trees and shrubs;

Field Of Science
1060 - Biology (whole systems);

Keywords

root pruning

structural pruning

landscape stability

pruning standards

root defects

red maple

highrise oak

live oak

allee elm

ansi a-300

Goals / Objectives
Guidelines for pruning roots at planting and pruning roots on established trees to treat stem girdling roots and other root defects will be described in the forthcoming ANSI A-300 root management standards. Guidelines for pruning the tops of trees are based on anecdotal experience and the ANSI A-300 pruning standards. Guidelines for producing high quality root systems in tree nurseries are not currently published. Research to support these standards is just beginning. This project seeks to determine 1) the influence of root pruning techniques during nursery production and at planting on growth and stability in the landscape 2) influence of root pruning large established trees on growth, decay, and stability in the landscape, and 3) influence of top pruning strategies on stability and breakage in storms. We will evaluate the efficacy of removing roots that circle and dive on the outer edge of container root balls and those that cross over the tops of major flare roots. One and two years after planting stability will be evaluated by measuring force required to pull trees over to a set angle; force required to pull over root pruned trees will be compared to trees not root pruned at planting. Reformation of root defects following pruning will be evaluated in the years following root pruning. Part two of this project seeks to determine the relationship between diameter of cut roots and ability to regenerate new roots and to decay. Roots from one to 6 inches diameter were severed 2006 on 30 inch trees; the proposed research will excavate these roots 3 years after pruning (2009) to evaluate decay and root regeneration. Part three evaluates influence of structural pruning and other pruning strategies in reducing tree damage in storms. This project is designed to answer the questions: 1) does removing root defects formed in the nursery increase tree stability after planting, 2) do roots of a certain diameter on large trees die back and decay instead of regenerate new roots, and 3) can pruning reduce tree damage in wind storms

Project Methods
Study 1: 'Florida Flame' red maple and Allee elm were planted into #3 containers in June 2005 at 0.5 or 2.5" deep, then potted to #15 at 0.5 or 2.5" deep and finished in #45 at grade. Trees were planted to the landscape on 12 ft centers March 2008 with either roots over root flare removed or not removed with two mulch treatments. Time required to remove root defects was recorded for trees root pruned. Experimental design: 2 species (maple and elm), 2 container planting depths (1" or 5" deep), 2 root pruning (defects removed or not removed), 2 mulch treatments (36 ft2 mulch around but not on root ball or 36 ft2 mulch around and on root ball), 5 reps. Measurements taken during the next three years: root growth into landscape soil, root defects at flare, caliper and height, force required to pull trees over to a set angle. Study 2: Highrise live oak were planted from rooted cutting in June 2005 and repotted to a series of larger containers until finished in #15 containers March 2008 when they were planted to the landscape. Experimental design: 3 root prunings x 4 reps = 48 trees. The 3 root prunings: root prune by removing edge and bottom inch of root ball and remove top defects; slice root balls top to bottom 3 to 4" deep with balling spade and remove top defects; no root pruning. Measurements to be taken during next three years: caliper and height, force required to pull tree to a set angle, root growth, root deflection and root straightness. Study 3: Roots from 1 to 6" diameter were cut October 2006 on live oaks with trunks averaging 30" dbh to evaluate relationship between root cut diameter to root regeneration and decay. Eight to 14 roots on each of 10 trees were severed about 2' from the trunk. Cut roots were chosen to represent a range of diameters from 1" to 6". In October 2009 cut roots will be excavated to measure diameter of each cut, root regeneration and root decay on cut roots. Decay volume will be quantified by taking thin cross sections through roots behind the cut. Study 4: Fourteen 'Florida Flame' red maple trees are spaced 16 ft apart in a single row and crowns are not touching. Seven trees will be structurally pruned and seven will not be pruned by pairing similar trunk by dbh and crown structure. Trees will be pruned by removing one-third of the foliage from the tree about one week prior to testing. Wind will be generated by a set of 8 turbojet fans driven by four turbo- engines each generating approximately 625 hp mounted on two 20-ton trailers. Wind data collected from real hurricanes will guide in duplicating the turbulence experienced in a real storm. Water will be introduced in the wind stream through 120 nozzles in front of the wind field designed to provide as real a storm event as possible. As the tree is blown, trunk motion will be tracked by 3 accelerometers and 3 inclinometers positioned along the trunk in the crown and below the crown. Wind speed on the windward side of the crown will be measured. Data will be collected at 50 Hz. Throttles will increase wind speed from zero to 90 mph over a two minute period and kept at 90 mph for three minutes.

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Results have been desseminated through many extension educational session in Florida (8 programs) and other states (7 programs) and countries (3 countries) which includes more than 2,000 attendees. Colleagues also read the one scientific publication that resulted this year from the project. Also, the book mentioned below is in the hands of at least 800 people so far in 2011. PARTICIPANTS: Partner organizations that contributed include a group of companies that provide financial support through the Florida Nursery Growers and Landscape Association. Dr. Jason Grabosky from Rutgers continues to be a part of my program as we have and continue to collaborate on various projects. Dr. Forrest Masters from Civil and Coastal Engineering Department is also involved in several of the studies that are part of this project. He has contributed his wind engineering knowledge to our stability evaluations and provides assistance with complex mathematical calculations. TARGET AUDIENCES: I know of at least 15 to 20 nurseries and many landscape installation firms in Florida, California, and other places that have changed their practices when they either shift trees from one container size to the next or when they plant trees into the landscape soil. They now prune roots in the manner we describe to reduce root defects. Several have modified the procedure to fit their operation, others have used it as we teach it. Many arborists are using canopy reduction pruning practices on selective upright stems on shade trees to reduce tree failures in storms. Others have implements structural pruning techniques we developed as part of this project. This has become more popular as arborists have begun using the practice and adjusting it to their species and experiences. Arborists report less tree faliures following recent storms and hurricanes in southeast US when trees are pruned in this manner. PROJECT MODIFICATIONS: None

Impacts
As a result of this research program a new trade association is forming called ACT (Association of Certified Tree Growers) among tree growers in Florida. Their mission if to certify that trees have been grown according to the research discoveries made during the course of this project. This will improve the quality of tree root systems reaching the market place ultimate ensuring better anchorage to the soil in future storms. This will reduce the amount of damage to infrastructure caused by tipped trees in hurricanes, and reduce the damage to trees themselves in storms. Trees were found to be better anchored to the ground as a result of root pruning treatments applied to trees as they were transferred from one container size to the next in a tree nursery. Also, trees were better secured to the landscape soil following planting. This means that there will be less damage in the next hurricane as a result of applying these treatments. Moreover, certain pruning strategies applied to the branches resulted in stronger structure and better stability in storms.

Publications

• Gilman, E.F., and J.C. Grabosky. 2011. Quercus virginiana root attributes and lateral stability after planting at different depths. Urban Forestry Urban Greening. 11:3-9.
• Gilman, E.F. 2011. An Illustrated Guide to Pruning, Third edition. Delmar, Cengage Learning, Albany, NY. 476 pgs., color.

Progress 10/01/08 to 09/30/11

Outputs
OUTPUTS: Last report should have been marked final. This is to close project. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Last report should have been marked final. This is to close project.

Publications

• No publications reported this period

Progress 10/01/09 to 09/30/10

Outputs
OUTPUTS: Results have been disseminated by including appropriate practical applications on the "Landscape Plants" web page in the Environmental Horticulture department. This site receives an average of 22,000 monthly page views. Moreover, this information reaches the approximately 5,000 professionals I speak to annually and various conferences. PARTICIPANTS: Partner organizations that contributed include a group of companies that provide financial support through the Florida Nursery Growers and Landscape Association. Dr. Jason Grabosky from Rutgers continues to be a part of my program as we have and continue to collaborate on various projects. Dr. Forrest Masters from Civil and Coastal Engineering Department is also involved in several of the studies that are part of this project. He has contributed his wind engineering knowledge to our stability evaluations and provides assistance with complex mathematical calculations. TARGET AUDIENCES: I know of at least 12 to 15 nurseries and many landscape installation firms in Florida, California, and other places that have changed their practices when they either shift trees from one container size to the next or when they plant trees into the landscape soil. They now prune roots in the manner we describe to reduce root defects. Several have modified the procedure to fit their operation, others have used it as we teach it. Many arborists are using canopy reduction pruning practices on selective upright stems on shade trees to reduce tree failures in storms. Others have implements structural pruning techniques we developed as part of this project. This has become more popular as arborists have begun using the practice and adjusting it to their species and experiences. Arborists report less tree faliures following recent storms and hurricanes in southeast US when trees are pruned in this manner. PROJECT MODIFICATIONS: None

Impacts
Techniques developed through this project are being used by tree growers throughout the US, and in different countries to improve tree anchorage in storms that occur in urban and suburban areas. Arborists also are incorporating these new techniques into their service line offered to their customers. Trees are more stable in wind as a result of these treatments. Treea are less likely to incur health problems as a result of removing roots that wrap the trunk. These techniques are being developed through this project.

Publications

• Gilman, E.F., C. Harchick, M. Paz. 2010. Effect of tree size, root pruning and production method on establishment of Quercus virginiana. Arboriculture and Urban Forestry. 36: 183-190.
• Gilman, E.F. and F. Masters. 2010. Effect of Tree Size, Root Pruning and Production Method on Root Growth and Lateral Stability of Quercus virginiana. Arboriculture and Urban Forestry. 36: 281-291.
• Gilman, E. F., C. Harchick, and M. Paz. 2010. Planting depth affects root form of three shade tree cultivars in containers. Arboriculture and Urban Forestry 36:132-139.
• Gilman, E.F., M. Paz, and C. Harchick. 2010. Effect of container type on root form of red maple. Journal Environmental Horticulture. 28:1-7.
• Gilman, E.F., M. Paz, and C. Harchick. 2010. Root ball shaving improves root systems on seven tree species in containers. Journal Environmental Horticulture. 28:13-18.

Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: Activities: Began, completed, analyzed data, or continued the following experiements. 1) Impact of root ball shaving on root ball quality in containers. 2) Effect of container type on root form and growth of red maple. 3) Pruning roots affects tree quality on container-grown oaks. 4) Growth partitioning three years following structural pruning of Quercus virginiana. 5) Influence of nursery production system and staking on red maple stability in wind, 6) Root ball shaving at planting affects root growth and stability of southern magnolia 3 years after planting. 7) Root ball shaving at planting impact on maple and oak stability following landscape planting. Concepts of root pruning at planting were incorporated into the Arboriculture class which had 27 students this year. Events: Concepts of root pruning and tree stability were presented in lecture and/or demonstrated at the following conferences: Great Southern Tree Conference Dec 2008, Landscape Inspectors Association conference May 2009, Trees Florida June 2009, Roots Plus Growers Association annual conference May 2009, ISA International ann conference Rhode Island July 2009, Arboreta and Botanical annual conference, northeast chapter Philadelphia Aug 2009, Italian east coast ISA ann meeting, Rimini Oct 2009. Services: Visited several nurseries to demonstrate root pruning on trees. Products: Web site pages http://hort.ifas.ufl.edu/woody/rootprunesummary.shtml were added to my urban tree management web site. Dessemination: A public broadcasted TV segment was filmed and aired in summer 2009 on root pruning at planting. PARTICIPANTS: Collaborators: Dr. Forrest Masters, Civil and coastal engineering department, University of Florida. TARGET AUDIENCES: Target audiences: Landscape architects, arborists, wholesale tree growers, landscape management firms. Efforts: Approximately 5,000 professionals recieved information about root and crown pruning practices based on research from this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
I know of at least 8 to 10 nurseries and many landscape installation firms in Florida and California that have changed their practices when they either shift trees from one container size to the next or when they plant trees into the landscape soil. They now prune roots in the manner we describe to reduce root defects. Several have modified the procedure to fit their operation, others have used it as we teach it. Many arborists are using canopy reduction pruning practices on selective upright stems on shade trees to reduce tree failures in storms. This has become more popular as arborists have begun using the practice and adjsuting it to their species and experiences. Arborists report less tree faliures following recent storms and hurricanes in southeast US when trees are pruned in this manner.

Publications

• Gilman, E.F., C. Harchick, and C. Wiese. 2009. Pruning roots affects tree quality in container grown oaks. J. Environmental Horticulture 28(2): 13-18.
• Gilman, E.F. and B. Kempf. 2009. Strategies for growng a high quality root system, trunk, and crown in a container nursery. Urban Tree Foundation. 28 pgs.