A Quick Review of SGRs
Tree Care Advisor Core Course Training
Stem Girdling Roots
Approximately 20 year old root system of linden
Stem Girdling Roots and Stem Girdling Suckers: 6 year old Tilia cordata 5� deep
Effects on Landscape Lives Predisposition to other problems
Stunted growth Premature death/failure Reduced ability to compartmentalize
Predisposed Health
Predisposed Health
Predisposed Health
Predisposed Health
Effects on Water Balance
Constricted Sapwood/Water Flow
Sapwood Compression from SGRs
Photo Courtesy of Jeff Somebody
Predisposed Health
Predisposed Health & Reduced Ability to Compartmentalize
Predisposed Health
Stunted Growth
Premature Death
Premature Death
Premature Death
Premature Death
A Survey of Practitioners : North American Members of ISA (1998, n = 282)
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
Depth of Soil over Roots Surveys: Sites and Selection Minneapolis 1997 - Acer saccharum, 1999 - Fraxinus pennsylvanica, 1999 - Tilia cordata, Rochester 2001 - Celtis occidentalis, Saint Paul 2004 - Gleditsia triacanthos
N = 100 (+/-)Per Species, Randomly Selected
Depth of Soil Over Roots: Survey Protocol •3-9” d.b.h. Trees •Surveys included two teams. •1st Team “blind” condition rated canopies and stems •0-4 Rating System
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
Frost Crack
Dead Cambium
Depth of Soil over Roots Surveys: Root Collar Exams •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.
Summaries •Majority Had > 1” Soil Over Roots* •Tilia, Acer and Fraxinus Worst: > 90% w/4”+ •1”+ Soil = More SER’s (Stem Encircling Roots)
•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.
Premature Failure in Loading Events
When Roots and Stems Conflict
Soil Line
SGR compression point
Storm Damage in Minnesota: 1998 n=564
1995-2005 n=1584
Total Tree Failures In Boulevards Most Commonly Damaged Size (d.b.h.) ranges Size (d.b.h.) Range 6-10 inches
1998 % of Total 28.6
1995-2005 % of Total 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: Failures due to Stem Girdling Roots 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: SGRs below ground with compression
Norway Maple (Acer platanoides)
Storm Damage in Minnesota: 1998 n=564
1995-2005 n=1584
Commonly Damaged Species with Chronic Problems 1998 Little Leaf Lindens: 73% of all that failed were 4�+ deep and had stem girdling roots causing stem compression. These trees failed below the stem compression points.
1995-2005 76%
Stem Girdling Suckers
Stem Girdling Suckers
Stem Girdling Suckers
Treatments?
Treatments?
Treatments?
Treatments?
Treatments?
Mark Dungan
Treatments?
Treatments?