Structural Pruning Adds No Branch Union Strength to Callery Pear

Summary: Structural pruning adds no branch union strength to Callery pear, according to an article in the May 2021 issue of Arboriculture & Urban Forestry.

Callery pear trees appeal to owners and passersby because of their year-round interest, with their most famous attractiveness white flowers in early spring. They have a downside in that their straight, vertical limbs suffer from embedded, included bark and therefore from severe breakage during such extreme loading events as inclement natural events and, as the world witnessed in 2001, unfriendly human takeovers; night silhouette of Callery pear tree during freezing rain, Franklin Farm Village Shopping Center, Franklin Farm section of Oak Hill, Fairfax County, Northern Virginia; Tuesday, Feb. 16, 2016, 02:05: Famartin, CC BY SA 4.0 International, via Wikimedia Commons

Structural pruning adds no branch union strength to Callery pear, according to an article, in Arboriculture & Urban Forestry May 2021, by one New Jersey-, one West Virginia- and two Ohio-based co-authors.

The article Structural Pruning in Callery Pear Does Not Change Apparent Branch Union Strength in Seventh Year Static Load Field Testing broaches urban environment-tolerant Callery pear. The Bradford cultivar (Pyrus calleryanna Decne. ‘Bradford’) cheers early spring with white flowers and configures ice-, snow-, wind-sensitive embedded, included bark and long, taperless, vertical limbs. Branch union strength decreases for codominant, forked branches descriptive of Callery pear cultivars, developing from the same branch junction and displaying bark-included divisions and near-same diameters.

Aspect ratio of branch or stem size to parent or trunk size, not branch attachment angle, exposes branch attachment strength just beyond branch-trunk and codominant-branch unions.

Branch attachment strength favors one branch or codominant stem figuring two-thirds-plus smaller in diameter than its parent branch or tree trunk or than another codominant stem.

Moisture content gauges branch attachment and union inversely in greater wood stiffness and strength respectively at or below fiber saturation point (35 percent) and lesser beyond. Structural pruning heaves and hones branches and stems to help attachment strength, growth rate, orientation, shape and size and to harvest lasting branch and trunk arrangements. It involves establishing each tree's dominant leader and removing broken, dead, dying, trunk-choking branches and lower branches from the tree base 4.5 feet (1.4 meters) upward.

No such natural occurrences as high winds and ice storms and no pests apart fire blight (Erwinia amylovora) jeopardized branch union strength or structural pruning schedules.

Dry mass (oven-dryed at 214 degrees Fahrenheit [101 degrees Celsius]) from 1- to 4-inch [2.5- to 10.2-centimeter]) wet-mass cross-sections, over dry mass kindled calculated moisture content.

The seven-year research in central, northern and southern Ohio lodged 1- to 3-foot- (2.5- to 7.6-centimeter-) long trunks, each with one branch attachment, to breaking devices. Pruned- and unpruned-tree diameters at 1.37-meter (4.5-foot) breast heights (DBH) manifested, in 2012, 2-centimeter (0.79-inch) and, in 2018, respectively 11.2- and 11.7-centimeter (4.41- and 4.61-inch) growth. Forty-nine unpruned Callery pear Redspire cultivars netted, in 2012 and 2018, 281.9-centimeter (110.98-inch) and 678-centimeter (266.93-inch) height increases and 102.3-centimeter (40.28-inch) and 368-centimeter (144.88-inch) width increases.

Forty-five trees on structural pruning schedules observed, in 2012 and 2018, 280.4-centimeter (113.54-inch) and 678-centimeter (266.93-inch) height increases and 92.1-centimeter (36.26-inch) and 334-centimeter (131.49-inch) width increases.

The Redspire cultivar of Callery pear presented pruned trees statistically petiter in diameters at breast height and in width but not statistically different in breaking strength.

Apparent breakage strength and aspect ratio, like branch strength and pruning versus non-pruning schedules and canopy positions of branch unions, quartered neither apparent nor significant relationships. Material properties remain constant once moisture content rises above 50 percent and unrelated to aspect ratio and breakage stress, branch departure angle and branch raw size. The seven-year study showed branch samples sheltering higher moisture content than trunk samples in 43 of 52 surveys and storing equal-sized water stocks in another five.

Co-authors Gregory Dahle, Jason Grabosky, Richard G. Rathjens and T. Davis Sydnor term structural pruning among things not triggering apparent branch union strength in Redspire cultivars.

A Callery pear (Pyrus calleryanna) tree managed to survive during the Sept. 11, 2001, attack on the World Trade Center and in the post-attack rubble thereafter. New York City Department of Parks and Recreation employees nursed the tree back to health despite the woody plant suffering broken, burned branches and snapped roots. The recovered, rehabilitated tree, with its moniker The Survivor Tree and with its post-2001, smooth limbs stretching outward from gnarled stumps, welcomes locals and visitors to the Ground Zero memorial site since 2010; Sunday, Jan. 12, 2012, night photo of The Survivor Tree: Shannon Wagner (Qwirty), CC BY SA 4.0 International, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Callery pear trees appeal to owners and passersby because of their year-round interest, with their most famous attractiveness white flowers in early spring. They have a downside in that their straight, vertical limbs suffer from embedded, included bark and therefore from severe breakage during such extreme loading events as inclement natural events and, as the world witnessed in 2001, unfriendly human takeovers; night silhouette of Callery pear tree during freezing rain, Franklin Farm Village Shopping Center, Franklin Farm section of Oak Hill, Fairfax County, Northern Virginia; Tuesday, Feb. 16, 2016, 02:05: Famartin, CC BY SA 4.0 International, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:2016-02-16_02_05_01_Freezing_rain_on_a_Callery_Pear_at_night_at_the_Franklin_Farm_Village_Shopping_Center_in_the_Franklin_Farm_section_of_Oak_Hill,_Fairfax_County,_Virginia.jpg

A Callery pear (Pyrus calleryanna) tree managed to survive during the Sept. 11, 2001, attack on the World Trade Center and in the post-attack rubble thereafter. New York City Department of Parks and Recreation employees nursed the tree back to health despite the woody plant suffering broken, burned branches and snapped roots. The recovered, rehabilitated tree, with its moniker The Survivor Tree and with its post-2001, smooth limbs stretching outward from gnarled stumps, welcomes locals and visitors to the Ground Zero memorial site since 2010; Sunday, Jan. 12, 2012, night photo of The Survivor Tree: Shannon Wagner (Qwirty), CC BY SA 4.0 International, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:The_Survivor_Tree_at_the_National_September_11_Memorial.jpg

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.

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Marriner, Derdriu. 13 April 2013. “Urban Tree Root Management Concerns: Defects, Digs, Dirt, Disturbance.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/04/urban-tree-root-management-concerns.html

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

Marriner, Derdriu. 14 April 2012. “Three Tree Risk Assessment Levels: Limited Visual, Basic and Advanced.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2012/04/three-tree-risk-assessment-levels.html

Marriner, Derdriu. 19 February 2012. “Qualitative Tree Risk Assessment: Risk Ratings for Targets and Trees.” Earth and Space News. Sunday.
Available @ https://earth-and-space-news.blogspot.com/2012/02/qualitative-tree-risk-assessment-risk.html

Marriner, Derdriu. 18 February 2012. “Qualitative Tree Risk Assessment: Falling Trees Impacting Targets.” Earth and Space News. Saturday.
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. 22 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

Rathjens, Richard G.; T. Davis Sydnor; Jason Grabosky; and Gregory Dahle. May 2021. "Structural Pruning in Callery Pear Does Not Change Apparent Branch Union Strength in Seventh Year Static Load Field Testing." Arboriculture & Urban Forestry 47(3): 123-130.

"The Survivor Tree." National September 11 Memorial & Musem > Visit > The Memorial. Copyrighted 2021.
Available @ https://www.911memorial.org/visit/memorial/survivor-tree