Extension News

Ask the ISU Extension Garden Experts: After the snow lawn questions

Note to media editors: Got gardening questions? Call the Hortline at (515) 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or send an e-mail to hortline@iastate.edu. For more gardening information, visit us at Yard and Garden Online, http://www.yardandgarden.extension.iastate.edu.


As the snow melted over the last few weeks, several narrow, meandering pathways appeared in my lawn. What produced them? Will the grass recover?

The runways in the lawn were likely caused by the meadow vole. The meadow vole is a small, brown, mouse-like animal. Though common in Iowa, the meadow vole is secretive and seldom seen by most individuals.

Voles are herbivores. They feed on grasses and other herbaceous plants. They also eat seeds, berries, tubers and bulbs. In winter, meadow voles may eat the bark of small trees and shrubs.

Meadow voles usually don’t cause serious harm to lawns. Damaged areas usually recover on their own within a few weeks. Reseeding may be necessary when damage is severe.

In lawns, vole populations can be kept to a minimum with regular mowing. Mow Kentucky bluegrass lawns at a height of 2 and one-half to 3 and one-half inches. Continue to mow the lawn until the grass stops growing in fall (typically early November in Iowa). Cut or destroy tall weeds adjacent to lawns and gardens to reduce food resources and cover.

Damage to young trees and shrubs can be prevented by placing one-fourth inch hardware cloth cylinders around plants. Bury the bottom two to three inches of the hardware cloth in the soil to prevent voles from burrowing under the cylinders. When mulching, keep wood mulches at least six inches from the trunks of small trees.

Since the snow has melted, I’ve begun to see circular, straw-colored patches in my lawn. What caused them? Are they a serious problem?

Snow molds may be responsible for the spots in your lawn. Two snow mold diseases, gray snow mold and pink snow mold, occur in Iowa. Gray snow mold is caused by two species of the fungus Typhula, while pink snow mold is caused by the fungus Microdochium nivale. Snow molds are most likely to develop after winters with extended periods of snow cover.

Symptoms of snow molds first appear when snow melts in late winter or early spring. Circular, straw-colored patches appear in the lawn as the snow recedes. Patches caused by gray snow mold may be a few inches to a few feet in diameter, while those caused by pink snow mold tend to be smaller, less than six inches across. These patches may continue to enlarge if the grass remains cool and wet. Grass in the patch may be matted and wet, with pink- or gray-colored fungal growth over the patch or on the edge. Gray snow mold causes small, pinhead-sized, round structures (sclerotia) to develop on the leaves and crowns of the grass plants.

Damage caused by snow molds is usually not serious. Affected areas typically green up, though more slowly than the rest of the lawn. Gently raking the affected areas may help to dry them out and prevent further fungal growth. In future years, problems with snow molds can be minimized by avoiding excessive nitrogen fertilization in fall, keeping the grass mowed until growth stops in fall, raking fallen leaves, and by not throwing or piling snow on problem areas. Affected areas will need to be overseeded if they fail to green up.

Contacts :

Richard Jauron , Horticulture, (515) 294-1871, rjauron@iastate.edu

Christopher Weishaar , Extension Communications and External Relations, (515) 294-1327, cweishaar@iastate.edu