Dysfunctional Root Systems and Brief Landscape Lives: Stem Girdling Roots and the Browning of our Landscapes

2010 Woody Plant Conference – Scott ArboretumGary JohnsonThe University of MinnesotaDepartment of Forest Resources

University of Minnesota Urban Forestry and Horticulture Institute (www.trees.umn.edu)

Gary Johnson, Professor and corresponding presenter. johns054@umn.edu, 612-625-3765. Chad Giblin, Research Scientist Jeff Gillman, Associate Professor Dave Hanson, Research Specialist Rebecca Koetter, Research Fellow Sean Peterson, Forestry Technician Andrea Dierich, Graduate Research Assistant Davin Shokes, Research Assistant Emily Hanson, Research Assistant

University of Minnesota Urban Forestry and Horticulture Institute

Some Average Life Spans

Bur Oak 250+ Years* Silver Maple 125+ Years* Boxelder 100+ Years* Jack Pine 80+ Years* Paper Birch 65+ Years* Ford F150 Truck 20+ Years** Urban Core Tree 7-10 Years***

*Silvics of North America. **I Hope. ***Moll, 1989

State of the Urban Forest – 1989G. Moll, American Forests

Average Tree Lifespans* “Downtown” Urban Trees: 7-10 years. Suburban Landscape Trees: 30-40 years. Rural Landscape Trees: 60-70 years. Native Undisturbed Sites: 150 years.

*Based on J. Kielbaso’s research

“Downtown” Urban Trees

“Suburban” Landscape Tree

“Rural” Landscape Tree

Native Undisturbed Sites

Tree Health Decline: Predisposing, Inciting and Contributing Factors

Predisposing: Chronic effects on health. Inciting: Short-lived, random events. Contributing: Opportunistic factors.

Common Predisposing Factors

Long-Term Drought Cold Hardiness Zones Confined Root Spaces Poorly-Drained Soil

Common Inciting Events

Seasonal Floods Non-Target Spray Drift Weed Trimmer/Lawn Mower Damage Wind Storms

Common Contributing Agents

Armillaria Root Rot Two-Lined Chestnut Borer Bronze-Birch Borer Target Cankers

Dysfunctional Root Systems as Primary Predisposing Factors

Normal Functional Root Systems

Soil Line

Branch Root

Fine Root

6 year sugar maple root system from seed

Normal Functional Root Systems

White spruce root system

Pat Bartlett – Bartlett Forestry

Normal Functional Root Systems

Abnormal but Functional Root Systems: Gravel Bed Root Systems

Abnormal but Functional Root Systems: Adventitious Roots

Dysfunctional Root Systems as Primary Predisposing Factors

Photo by Dave Hanson

Photo by Eric Berg

Dysfunctional Root Systems as Primary Predisposing Factors

Dysfunctional Root Systems as Primary Predisposing Factors

Approximately 20 year old root system of linden

Dysfunctional Root Systems as Primary Predisposing Factors

Dysfunctional Root Systems as Primary Predisposing Factors

Dysfunctional Root Systems as Primary Predisposing Factors

Problems With Dysfunctional Root Systems

Reduced Root Spread Limited Water and Nutrient Uptake Reduced Photosynthetic Potential Reduced Energy Reserves

Problems With Dysfunctional Root Systems: Reduced Energy Reserves

Problems With Dysfunctional Root Systems: Water and Nutrient Stress

Problems With Dysfunctional Root Systems: Reduced Photosynthesis

Problems With Dysfunctional Root Systems: Reduced Stability

Photo by Eric Berg

Problems With Dysfunctional Root Systems: Reduced Stability

Photos by Kameron Kytonen

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

Diagnosing Dysfunctional Root Problems: What’s Wrong Here?

All Trees Suffered From Same Problem…

Stem Girdling Roots: a Primary Predisposing Factor

Stem Girdling Roots and Storm Failures

Photos by Eric Berg

•32% of all tree failures

•26% of all boulevard tree failures

•68% of Little-leaf Lindens in boulevards

•> 90% of trees that had SGRs had stems buried 4” or more.

Storm Damage in Minnesota: Failures due to Stem Girdling Roots (1995-2005 n=1584)

Root Collar Examinations as a Diagnostic Tool

Photo by Dave Hanson

Treatment Decisions

Photo by Dave Hanson

Treatment Decisions

Photo by Dave Hanson

Treatment Decisions

Photo by Dave Hanson

Treatment Decisions

Photos by Mark Dungan

Treatment Decisions

Photos by Mark Dungan

Treatments: 2 Years Later

Soil Line

Treatments: 8 Years Later

Treatments: 8 Years Later

8.5” SGR Removed

Treatments: 8 Years Later

Treatments: 8 Years Later

Treatments: 5 Years Later

Not All Treatments Were Successful

6 Years Post Treatment

Not All Treatments Were Successful

4 Years Post Treatment

Treatment Success often Species Dependent

30 Ohio Buckeye. 2” Caliper at Planting. Depth Correction of as Much as 9 inches.

6 Years After Planting

Prevention When Possible

Prevention When Possible

Trees Are Planted Deep to Prevent Leaning

Does it Work? No!*

2002 University of MN/Bailey Nursery Experiment

4 Tree Species, 460 Trees Total

4 Planting Depths: 0 – 2 – 4 – 6 Inches

Results? All Leaned at Same Rates

How Often Does it Happen?

881 Trees Sampled out of 5500 Total B&B and Containerized 87%: Stem Buried 2+ Inches 50%: Stem Buried 4+ Inches

*Minneapolis Park and Recreation Board; St. Paul Division of Forestry

Nursery Stock Survey 2001-2002*

Prevention When Possible

Assume That It Is Too Deep

Correcting the Problem: 1

Correcting the Problem: 2

Correcting the Problem: 3

Correcting the Problem: 3

Correcting the Problem: 4

Correcting the Problem: 5

Avoiding Other Root Problems:

Stem Girdling Root

Correcting the Problem: 5

Stem Girdling Root Removed

Correcting the Problem: 5

Correcting the Problem: 5

Stem Girdling and Encircling Roots

Correcting the Problem: 5

Correcting the Problem: 5

Correcting the Problem: 5

Removal Completed

Prevention When Possible

Photos by Stephen Schott

Problem Corrected At Planting Time

Controlling Variables: Planting Depth

Prevention When Possible

Photos by Dave Hanson

Does This Work? Probably Not.

Prevention When Possible

Photo by Dave Hanson

“Boxing” Pot-Bound Root Systems

Prevention When Possible

Photo by Dave Hanson

“Boxing” Pot-Bound Root Systems

Prevention When Possible

Photos by Gary Johnson

Alternatives to “Containers”: Root Bags

Prevention When Possible

Photos by Gary Johnson

Alternatives to “Containers”: Air Pruning Pots

Recovery of Root Systems in Gravel Beds

Recovery of Root Systems in Gravel Beds

Recovery of Root Systems in Gravel Beds

This Presentation Available by 10/26/10

www.trees.umn.edu Gary’s Notes

Woody Plant Conference