What is that?

• A girdling root is one that circles the base of a tree at or just below the surface.
• Gridling roots can also girdle other roots, but without harm.
• The most commonly affected species are maples, lindens, and ashes.

• The threat of a girdling root depends on two major factors:
• the size of the root
• the amount of circumference affected
• The expansion of the root and the stem squeezes them against each other, interfering with the transport of water, nutrients, sugars, and other necessary compounds.
• The resulting damage to the tree reduces vigor, and often leads eventually to whole stem failure.


Norway maple with girdling root tipped over in a windstorm

• The only sure sign is to see a root circling the main stem at or just below the soil surface.
• probe the soil at the tree base with a stiff wire to see if a circling root lies under the surface
• excavate the soil at the tree base to reveal any underground girdling roots
• Common symptoms include
• one side of the trunk flattened
• marginal and/or tip scorching on the leaves
• crown discoloration or dieback
• Many of these symptoms can be caused by other factors such as root damage, flooding, or wilt diseases.

• Prevention:
• carefully inspect the root system at the time of transplantation
• bend roots away from the stem before backfilling
• cut any roots (shaped like a "J") that curl back around the stem
• Treatment:
• use a saw or chisel to sever the girdling root, especially if the tree has a significant target
• reduce stress on the tree recovering from the removal of a girdling root

Johnson, Gary R., and Richard J. Hauer.  2000.  A Practitioner's Guide to Stem Girdling Roots of Trees.  Impacts on Trees, Symptomology, and Prevention.  St. Paul, MN: University of Minnesota Extension Service.  For other information, advice and help on this topic, call offices of your State Urban Forestry Coordinator or University Extension service, or visit urban forestry web sites.