DEEP ROOTS RESEARCHUNRI Webcast – 08/13/08

“Dysfunctional Root Systems and Brief Landscape Lives”

Gary Johnson, Department of Forest Resources, University of Minnesota

University of Minnesota Urban Forestry and Horticulture Institute

Chad Giblin, Research Scientist

Jeff Gillman, Associate Professor

Dave Hanson, Research Specialist

Gary Johnson, Professor and corresponding presenter. johns054@umn.edu, 612-625-3765.

Rebecca Koetter, Research Fellow

Patrick Weicherding, Ext. Educator and Professor

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. ***Kielbaso, 1989

State of the Urban Forest – 1989J.J. Kielbaso

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.

“Downtown” Urban Trees

“Suburban” Landscape Tree

“Rural” Landscape Tree

Native Undisturbed Sites

What’s a “Normal” Root System?

5 month root system from seed (butternut)

6 year sugar maple root system from seed

Approximately 20 year old root system of linden

White spruce root system

Pat Bartlett – Bartlett Forestry

What are “Normal” Roots? Seed Propagated Roots

“Normal” Roots: Adventitious Roots

Abnormal Root Systems

Root systems that deviate from normal or average root systems.

Balled and Burlapped

Containerized Root Systems

Plug Trays

J-Roots

Boulevards, Medians, Planters

Boulevards, Medians, Planters

Dysfunctional Root Systems

Roots in unhealthy interactions within a plant system.

Dysfunctional Root Systems

Buried root system growing to surface

Dysfunctional Root Systems

Stem Encircling Roots

Dysfunctional Root Systems

Stem Girdling Roots

Dysfunctional Root Systems

Stem Girdling Roots and Stem Girdling Suckers

Dysfunctional Root Systems

Pot-Bound Root System

Effects on Landscape Lives

Predisposition to other problems Stunted growth Premature death/failure Reduced ability to compartmentalize

Regarding Stem Girdling Roots and Tree Loss,Practitioners Stated:

•Relationship to tree decline and death - 82%

of the time.

•Relationship to the sudden failure of trees –

18% of the time

A Survey of Practitioners : North American Members of ISA (1998, n = 282)

Predisposed Health

Predisposed Health

Predisposed Health

Reduced Ability to Compartmentalize

Premature Death

Premature Failure in Loading Events

Three “Deep Root” Studies

Frequency of Buried Root Systems. Stem Girdling Roots & Storm Failures. Correcting Pot-Bound Root Systems.

Frequency of Buried Root Systems in the Landscape

Decline in Canopy Condition Associated with SGRs and Tilia.

July 7, 2006. Tilia cordata “Greenspire”

Depth of Soil Over Tree Roots:A Survey of 5 Landscape Species

1. Range of Soil Depths over Roots2. Condition of Canopies and Stems3. Frequency, Extent, Location and

Impact of Encircling or Stem Girdling Roots

Minneapolis 1997 - Acer saccharum, 1999 - Fraxinus

pennsylvanica,1999 - Tilia cordata,

Rochester 2001 - Celtis occidentalis,

Saint Paul 2004 - Gleditsia triacanthos

Depth of Soil over Roots Surveys: Sites and Selection

N = 100 (+/-)Per Species, Randomly Selected

•3-9” d.b.h. Trees

•Surveys included two teams.

•1st Team “blind” condition ratedcanopies and stems

•0-4 Rating System

Depth of Soil Over Roots: Survey Protocol

Criteria for Condition Rating Trees:Canopy and Stem Conditions

Canopy Pts Stem

No Dieback.Characteristic Density for the species.60%+ Live Crown Ratio (L.C.R.).Symmetrical.

4.0

No cambial loss*.No decay.No cracks/seams.

~ 10-25% Dieback, orLoss of Density, or<50% L.C.R., orLoss of Symmetry.

3.0 ~ 10% cambial loss.One crack and/or one seam.

Condition Rating: Canopies 0-4 Rating System:

0 = Dead 4 = No obvious defects.

Canopy condition rating factors: Characteristic density for the Species, Live crown ratio (60% standard), Crown symmetry, Dieback.

Condition Rating: Canopies

E.g., Greenspire Littleleaf Linden to the right. Canopy condition reduced due to density.

Condition Rating: Stems Factors:

Lost Bark/Living Cambium, Cracks/Ribs, Decay, Contributing Agents. Stem Girdling Roots (above ground)

0-4 Rating System: 0 = No living cambium in stem, 4 = No obvious defects.

Condition Rating: Stems

Dead Cambium

Frost Crack

•2nd Team performed root collar examination:

•Data Recorded:•Depth to first order roots,•Frequency and location of Stem Encircling Roots (SERs) and Stem Girdling Roots (SGRs),•% of stem affected.

Depth of Soil over Roots Surveys: Root Collar Exams

Typical tools for root depth evaluations:

•Surveyor’s arrow

•Hand tools

•Wet/Dry vac

•Air knife

Depth of Soil over Roots Surveys: Root Collar Exam Protocol

Summaries

•Majority Had > 1” Soil Over Roots*

•Tilia, Acer and Fraxinus Worst: > 90% w/4”+

•1”+ Soil = More SER’s

•Most Vulnerable Species: Tilia, Celtis, Fraxinus

•Worst Condition Rating:Soil Depth – Tilia, Acer, Fraxinus

•Most Common SGR’s:Soil Depth – Tilia, Fraxinus, Celtis, Acer

What IS Too Deep?

Frequency of Stem Encircling Roots: 1-3 Inches*

Frequency of Stem Girdling Suckers: 5 Inches**

Frequency of Stem Girdling Roots: 1-3 Inches*

*Sugar Maple, Green Ash, Littleleaf Linden, Hackberry, Honeylocust

**Littleleaf Linden

What IS Too Deep? Negative Effects on Health?

Species Dependent. 1-3.5 inches was Too Deep. Johnson and Johnson, 1997

Johnson and Borst, 1999 Johnson and Hauer, 2000 Johnson, et al., 2006. Planting Depth Interim Report.

Where it Began?: Containerized Depth Problems

Too Deep? Assume That It Is

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*

Why Does it Happen? To Stabilize Trees in Containers.

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

Storm Failure Research:Most common pre-existing conditions

Storm Failure Triangle

Tree Condition and Defects

Loading Eventwind, ice, snow

Site Characteristics

Failure Potential

Gary Johnson, University of MN

Storm Failure:pre-existing conditions

Storm Failure:pre-existing condition

Premature Failure in Loading Events*

III. Most common pre-existing conditions: For all damage, separating preexisting conditions:

CONDITION % OF TOTALDecay Only 13Stem Girdling Roots (SGR) 12Included Bark Only 4Root Problems (other than SGR) 3Codominant Leaders Only 4Construction Damage Only 1

*Storm Damage 1995-2005; University of Minnesota

•Total Failures (Trees failed at or below ground line) Was Most Common Damage

Category = 54% of all damage,

•The presence of SGRs was the most common pre-existing condition (32%).

Storm Damage in Minnesota: 1995-2005 n=1584

What IS Too Deep?

Impact On Storm Damage to Trees? Most common reason for total failure:

Buried SGRs. Species dependent. 1-4 inches. Johnson, 2006. “Storm Damage in

Minnesota, 1995-2005.”

When Roots and Stems Conflict

Soil Line

SGR compression point

Layers of Stem Girdling Roots: Tilia

Soil Line

SGR Compression

Storm Damage in Minnesota: SGRs below ground with compression

Norway Maple (Acer platanoides)

Total Tree Failures In BoulevardsMost Commonly Damaged Size (d.b.h.) ranges

1998 1995-2005Size (d.b.h.) Range % of Total % of Total6-10 inches 28.6 29.0

>25 inches 25.7 26.0

20-25 inches 15.7 16.0

10-15 inches 14.3 14.0

15-20 inches 14.3 14.0

Storm Damage in Minnesota: 1998 n=564 1995-2005 n=1584

•32% of all tree failures , located on the edges of storms

•26% of all boulevard total tree failures (53% of 6-10” category)

•68% of Little-leaf Lindens that failed in boulevards (#3rd most common species)

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

Storm Damage in Minnesota: Failures due to Stem Girdling Roots1995-2005 n=1584

Commonly Damaged Species with Chronic Problems

1998 1995-2005

Little Leaf Lindens: 73% of all 76%that failed were 4”+ deep and had

stem girdling roots causing stem compression.These trees failed below the stem compression points.

Storm Damage in Minnesota: 1998 n=564 1995-2005 n=1584

Decline in Stem Condition Associated with SGR’s and Tilia

Stem Girdling Suckers!

•University of Minnesota Planting Depth Study 2000-2007

•Lindens at 5” depth = Higher Frequency of Suckering.

•Higher Frequency of Suckering = Stem Girdling Suckers and Higher Mortality Rate

Stem Girdling Suckers!

Stem Girdling Suckers

Stem Girdling Suckers

Correcting Pot-Bound Root Systems

Study One: 14 month experiment. 2 species (Tilia and Salix). 3 Treatments (slice, butterfly and

“tease”). No statistical differences between

treatments and controls on survival (100%) and root production.

Arboriculture & Urban Forestry, Volume 33, Issue 1, January 2007.

Correcting Pot-Bound Root Systems

Study Two: Five years. Four species: Acer platanoides, Acer x

freemanii, Thuja occidentalis, Malus sp. Two treatments: slicing, “boxing.” Data: survival, condition ratings, caliper

increase, root production.

Correcting Pot-Bound Root Systems

•Complete randomized block design.

•Control and 2 treatments.

•8 replicates.

•11-05 to 11-10 study.

Correcting Pot-Bound Root Systems

“Boxing”

Control

Scoring

Correcting Pot-Bound Root Systems

Results to Date (08-08-08): Mortality Rates: Controls:0; Slice

Treatment:0; Boxing Treatment:0. Condition Rating: No significant

differences. Growth Rates: No significant differences.

Other Research?

Douglas Airhart – Tennessee Tech U. Bonnie Appleton – VA Tech. Mike Arnold – Texas A & M Susan Day – VPI Donna Fare – U. S. National

Arboretum Ed Gilman – U of Florida Christina Wells – Clemson University

Other Research? J. Roger Harris, VPI Gary Watson,

Morton Arboretum David Williams and

Gary Kling, U of IL T. Davis Sydnor

and Richard Rathjens, Ohio State University

Other Research?