Urban Tree Root Management Concerns: Defects, Digs, Dirt, Disturbance

Summary: Angela Hewitt and Gary Watson of The Morton Arboretum examine planting defects, digs, dirt and disturbance as urban tree root management concerns.

Built environments contribute to urban tree root management concerns; water oak (Quercus nigra) with root problems caused by embedded concrete and metal objects: Randy Cyr/Greentree/Bugwood.org, CC BY 3.0 United States, via Forestry Images

Defects, digs, dirt and disturbance are urban tree root management concerns, according to Root Management Challenges on Urban Sites: Human Intervention in Root Development in the April 2013 issue of Arborist News.

Angela Hewitt and Gary Watson begin with the observation that "Conflict between human activity and tree roots is constant" since developments above-ground typically bring changes below-ground. They consider as examples of "human intervention in root development" cultivation of nursery stock in containers and fields and disturbance of and obstacles in urban soils.

Master arborists, master gardeners, master naturalists and tree stewards depend upon nursery-grown stock to supplement sturdy species, such as silver maples, that tolerate air-poor, penetration-resistant soils.

Construction practices for leveling soils, landscaping practices for moving transplants and nursery practices for nurturing seedlings encourage root-unfriendly "human intervention that does not exist in nature."

Adventitious root flares and girdling roots furnish examples of urban tree root management concerns when field-grown nursery stock follow extreme pruning and too deep transplanting schedules.

Healthy flares go downward and outward from natural soil lines while adventitious flares grow down and out from root shanks 12-plus inches (30-plus centimeters) below ground-level. Disturbed soils have to be removed by root crown air excavation tools to heap the depression back up to natural soil lines with well-aerated pea gravel. Removal during dormant seasons is the procedure for girdling roots, whose cause is severed lateral roots inspiring non-severed lateral roots to grow perpendicularly around trunk bases.

Nursery stock juggle roots circling and descending from jamming up against narrow container walls during too infrequent transplant schedules without shaving, or box-cutting, root ball exteriors.

Roots that spread from four to five sides of trunks, to distances twice the heights of tall trees and thrice those of wide, keep trees anchored.

The "excellent" growing conditions and the "high-quality" soils in nurseries, where "competition is minimized," lead to transplants too deeply, thinly and weakly flared in urban soils. Measurements of bulk densities for air-poor, compacted, drought- or waterlogging-prone, fill-and-rubble, nutrient-poor urban soils may rival those of concrete, at 2.2 grams per cubic centimeter. Severance by heavy equipment for building and maintaining infrastructure and underground wires at distances closer than thrice trunk diameters numbers among urban tree root management concerns.

Drainage-friendly, nutrient-rich gravels and ground-level mulches overcome compacted fills while air excavation and ground-penetrating radar obtain root locations that excavators operate directional boring equipment to avoid.

Built environments prove to be obstacle courses since compacted fill provides stable anchorage to such infrastructure as building foundations, impermeable pavements, retaining walls and sewer pipes.

Ratios of foundation depth to tree-to-building distances equivalent to thrice heights quantify cycles of stress-fracturing foundation subsidence in high shrink-swell soils that anchor "high-water" demand trees. Moisture and nutrient extremes around retaining walls and in sewer systems require math-based measures since roots resist growing into 20-foot (6.1-meter) gaps between them and obstacles. Math spaces trees at minimal 6- to 10-foot (2- to 3-meter) distances from pavements atop 6-inch (15-centimeter) gravel-and-rubble bases on 4-inch (10-centimeter) metal, plastic, polystyrene barriers.

The "intense competition for space in urban landscapes" takes its toll in urban tree root management concerns and its triumphs from inventive remediation of human intervention.

Deep planting encourages urban tree root management concern of adventitious roots forming on stems well above soil line; boxwood (Buxus spp.) with adventitious roots above soil line: Mary Ann Hansen/Virginia Polytechnic Institute and State University/Bugwood.org, CC BY 3.0 United States, via Forestry Images

Acknowledgment

My special thanks to:
talented artists and photographers/concerned organizations who make their fine images available on the internet;
University of Illinois at Urbana-Champaign for superior on-campus and on-line resources.

Image credits:

Built environments contribute to urban tree root management concerns; water oak (Quercus nigra) with root problems caused by embedded concrete and metal objects: Randy Cyr/Greentree/Bugwood.org, CC BY 3.0 United States, via Forestry Images @ http://www.forestryimages.org/browse/detail.cfm?imgnum=1238206

Overly deep planting encourages urban tree root management concern of adventitious roots forming on stems well above soil line; boxwood (Buxus spp.) with adventitious roots above soil line: Mary Ann Hansen/Virginia Polytechnic Institute and State University/Bugwood.org, CC BY 3.0 United States, via Forestry Images @ http://www.forestryimages.org/browse/detail.cfm?imgnum=5337028

For further information:

Gilman, Ed. 2011. An Illustrated Guide to Pruning. Third Edition. Boston MA: Cengage.

Hayes, Ed. 2001. Evaluating Tree Defects. Revised, Special Edition. Rochester MN: Safe Trees.

Hewitt, Angela; and Watson, Gary. April 2013. "Root Management Challenges on Urban Sites: Human Intervention in Root Development." Arborist News 22(2): 12-17.
Available @ http://viewer.epaperflip.com/Viewer.aspx?docid=20b3f7db-ef85-4964-969f-a29d00fc2957#?page=16

Marriner, Derdriu. 16 February 2013. “Tree Friendly Beneficial Soil Microbes: Inoculations and Occurrences.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/02/tree-friendly-beneficial-soil-microbes.html

Marriner, Derdriu. 15 December 2012. “Healthy Urban Tree Root Crown Balances: Soil Properties, Soil Volumes.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2012/12/healthy-urban-tree-root-crown-balances.html

Marriner, Derdriu. 13 October 2012. “Tree Adaptive Growth: Tree Risk Assessment of Tree Failure, Tree Strength.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2012/10/tree-adaptive-growth-tree-risk.html

Marriner, Derdriu. 11 August 2012. “Tree Risk Assessment Mitigation Reports: Tree Removal, Tree Retention?” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2012/08/tree-risk-assessment-mitigation-reports.html

Marriner, Derdriu. 16 June 2012. “Internally Stressed, Response Growing, Wind Loaded Tree Strength.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2012/06/internally-stressed-response-growing.html

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Available @ https://earth-and-space-news.blogspot.com/2012/04/three-tree-risk-assessment-levels.html

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Available @ https://earth-and-space-news.blogspot.com/2012/02/qualitative-tree-risk-assessment-risk.html

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Available @ https://earth-and-space-news.blogspot.com/2012/02/qualitative-tree-risk-assessment.html

Marriner, Derdriu. 10 December 2011. “Tree Risk Assessment: Tree Failures From Defects and From Wind Loads.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/12/tree-risk-assessment-tree-failures-from.html

Marriner, Derdriu. 15 October 2011. “Five Tree Felling Plan Steps for Successful Removals and Worker Safety.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/10/five-tree-felling-plan-steps-for.html

Marriner, Derdriu. 13 August 2011. “Natives and Non-Natives as Successfully Urbanized Plant Species.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/08/natives-and-non-natives-as-successfully.html

Marriner, Derdriu. 11 June 2011. “Tree Ring Patterns for Ecosystem Ages, Dates, Health and Stress.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/06/tree-ring-patterns-for-ecosystem-ages.html

Marriner, Derdriu. 9 April 2011. “Benignly Ugly Tree Disorders: Oak Galls, Powdery Mildew, Sooty Mold, Tar Spot.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/04/benignly-ugly-tree-disorders-oak-galls.html

Marriner, Derdriu. 12 February 2011. “Tree Load Can Turn Tree Health Into Tree Failure or Tree Fatigue.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/02/tree-load-can-turn-tree-health-into.html

Marriner, Derdriu. 11 December 2010. “Tree Electrical Safety Knowledge, Precautions, Risks and Standards.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2010/12/tree-electrical-safety-knowledge.html