Fixit: Stem-girdling roots may cut off tree's nutrient flow

Q An arborist said one of our honey locust trees might have "girdling roots." What are these, and how do they harm a tree?

By Karen Youso, Star Tribune

Last update: September 4, 2007 - 4:47 PM

Q An arborist said one of our honey locust trees might have "girdling roots." What are these, and how do they harm a tree?

A Stem-girdling roots (SGR) can be a serious problem for trees. Instead of growing away from the tree trunk, stem-girdling roots start wrapping around the tree trunk. As the roots grow, they can actually cut off water and nutrient flow in that part of the trunk. The compression of the trunk caused by SGRs also weakens the tree's structure, making it more susceptible to failure (falling over) in a storm.

Gary Johnson, professor of Urban Forestry at the University of Minnesota, has done considerable work on this subject. His findings include evidence that planting trees too deeply often results in growth of SGRs.

Nancy Rose, horticulture educator, University of Minnesota Extension

Springtail invasion

Q We are experiencing an invasion of springtails, an insect we've never had before. I guess the recent heavy rains have brought them out. Are they harmful and how do we get rid of them?

A Springtails prefer to live in damp areas, where they feed on decaying vegetation, fungi, pollen and other organic material, according to Jeff Hahn, extension entomologist at the University of Minnesota Extension. They occur in the soil outdoors in tremendously large numbers.

Springtails will enter homes if their environment becomes dry, but they can survive indoors only if they find a damp area that can provide them food, such as the soil of potted plants (when soil is overwatered or if the soil is composed of highly organic matter). Springtails are harmless but can be a nuisance when there are too many of them.

Normally, drying out springtail-infested areas with a fan or dehumidifier is sufficient to control them. Also, look for a source of moisture, perhaps a plumbing leak, and repair it. Insecticides aren't very effective against springtails as long as an environment favorable to them exists.

If you believe that recent wet weather is responsible, be sure you take a good look at the outside of your home. Make sure that rain gutters are clean and free flowing, and that downspouts carry water at least 10 feet from the foundation. Also, be sure it's the soil and not landscaping rock or mulch that is sloping away from the house. Over time, the actual soil around a house will settle and slope toward the house, which can keep the soil near the foundation moist and invite bugs such as springtails. Because they like decaying vegetation and fungi, check for them in any mulch near your home or in woodpiles and such; you may need to remove the piles to get rid of the bugs.

Send your questions to Fixit in care of the Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-9033, or e-mail fixit@startribune.com.