Winterkill is a generic term used to describe the death of grasses during the winter. Two types of winterkill we may see this year include desiccation and crown hydration.
Desiccation occurs when the turf is unprotected by snow cover and there are cold, drying winds for extended periods of time during the winter. The exposed grass can lose moisture in crown tissues, which sit just at the surface of the soil, resulting in death of the plants.
All cool season grasses, which are the most commonly used grasses in Utah, can suffer from winter desiccation injury.
Crown hydration is the most common and destructive type of winter injury, and usually occurs in late winter following periods of thawing and freezing.
During late winter months, temperatures may rise above freezing for a few days at a time. When this happens, some grasses begin to grow and crowns become hydrated.
If a rapid freezing event follows the thaw, ice forms inside the crowns of turf grasses and will either rupture cell membranes or draw moisture out of the cells.
So, what happens after winterkill of grasses?
Sometimes, an area of grass will appear dead, but many of the plants still possess viable crown tissue. You can assess recovery potential by taking plugs of damaged grass and placing these in a warm, well-lit area for several days or weeks to determine if regrowth occurs.
Just because a few tillers emerge from the plugs does not necessarily mean the area will fully recover, but this method can help you decide whether reef-seeding will be required.
This is Kelly Kopp, USU Extension water conservation and turf grass specialist, wishing you a happy winter and healthy turf.
More information on this and other topics can be found on the USU Extension website.