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

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)

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 rated

canopies and stems

•0-4 Rating System

Depth of Soil Over Roots: Survey

Protocol

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

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

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

1998 1995-2005

Size (d.b.h.) Range % of Total % of Total

6-10 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 Roots

1995-2005 n=1584

Storm Damage in Minnesota: SGRs below ground with compression

Norway Maple (Acer platanoides)

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

Stem Girdling Suckers

Stem Girdling Suckers

Stem Girdling Suckers

Treatments?

Treatments?

Treatments?

Treatments?

Treatments?

Mark Dungan

Treatments?

Treatments?