What is “Winterkill Grass?”
“Winterkill” is a catchall term used to describe lawn problems after winter. It is caused by a variety of factors such as desiccation, crown hydration, cold temperatures, ice sheets, and snow mold. Winter lawn damage varies greatly depending upon environmental conditions as well as other factors such as drainage and the type of grass being grown.
Why has My Lawn Died over Winter?
Low temperatures are one of the biggest causes of winterkill grass. Cool-season grasses are generally well adapted to cooler temperatures but some fare better than others. Roughstock, creeping bentgrass, and bluegrass fare the best while perennial and annual ryegrass are the most susceptible to winterkill. Turf grass undergoes a process called “cold acclimation” wherein some sugars and proteins accumulate, cell walls become fluid, and cells dehydrate. This is all to help the grass tolerate low temps. The crown or growing point of the grass is normally insulated by the soil, but warm days in the late winter result in the plants taking up water only to be followed by days of rapid freezing. This results in crown hydration which ruptures the plant cells resulting in dead grass spots or areas. Snow mold may be another reason for winter lawn damage. Typhula blight (gray snow mold) and Microdochium patch (pink snow mold) are the most common fungi. Gray snow mold needs extended snow cover while pink can occur with or without snow cover.
How to Revive Winterkill Grass
There isn’t much you can do about cold winter temperatures, but you can plant the more resistant grass strains: Roughstock, creeping bentgrass, or bluegrass are the most resistant to winterkill followed by Kentucky bluegrass, Colonial bentgrass, and creeping red fescue. As to snow mold, a preventative fungicide is the best control application. Worst case scenario is that you may need to reseed or sod again. Before taking any drastic action, test to make sure the culprit is winterkill. Remove sod samples from areas of concern and samples from areas that appear healthy. Pot each sample in soil-filled containers making sure to label the containers accordingly. Keep moist and place under a grow light. Monitor for greening up. Grass that will survive will begin to green up in response to warmth, moisture, and light in about 14 days.
