Welcome to the latest issue of the Home Lawn Care Newsletter from UMN Turfgrass Science! We will provide up-to-date information to address all your lawn care tasks at the times when you need to know.
January 16, 2024: Issue 18
What causes some grass to die in the winter?
Even though winter took a while to arrive this year in the Upper Midwest, we finally have some snow and the low temperatures we are used to during the short days of mid-January. While you patiently wait to begin taking care of your lawn in the spring, you might be wondering about how winter affects the grasses we grow in Minnesota. There are a number of weather-related reasons why part or all of your lawn may die in the winter, several of which have to do with moisture regulation inside the plants. The five main types of winter injury or death of turfgrasses are desiccation, ice encasement, crown hydration, low temperature kill, and snow mold.
In the case of desiccation, turf that is not protected from snow cover can be more exposed to winter winds, which dry out the plants. This is a problem because plants still need some moisture throughout the winter because they are still respiring. Even with typical snow cover years, you can find desiccation damage on slopes where the snow has melted or drifted, leaving the turf area exposed to the wind.
Ice encasement is when a layer of ice has formed around the plant tissues, which blocks the exchange of gases, causing a build up of gases like carbon dioxide as they respire throughout the winter. Ice encasement is most commonly found in low-lying areas that hold water.
Low temperature kill happens most often with warmer falls followed by a sudden change in weather pattern to freezing temperatures. In this case, the plants have not had the chance to acclimate to the gradual lowering of temperatures throughout the fall and early winter. Most grasses we use on lawns in Minnesota can survive the very low temperatures we have, especially when they’ve gone through a fall acclimation period.
Crown hydration tends to happen as a result of warm-ups (above freezing) during the winter. When temperatures get above freezing, plants will begin taking in water and re-hydrating. If there is then a sudden drop in temperatures to well below freezing following this rehydration, the moisture inside the plant (especially the crown), can freeze and cause plant cells to rupture, resulting in the death of these tissues and plants.
Snow mold is a disease that attacks plants during the winter, but it seldom causes death. Combined with other stresses, some turf species can be killed by snow mold; this is more likely to be the case in regions where snow is deep and persistent throughout the winter. Generally, snow mold just delays spring green-up as the lawn grows out of the injury.
Learn about the WinterTurf research project where we are learning more about these winter stresses.
What can we expect for winter injury so far this winter?
For much of Minnesota, this has been a very mild winter, with below-average snowfall and the warmest December on record. Although the temperatures have been warmer than normal, the lack of insulating snow could set up some lawns for desiccation injury. The lack of snow may also indicate reduced snow mold pressure this winter. However, snow mold doesn’t necessarily require snow cover, and there is plenty of winter remaining. For now it is a little too early to know for sure how this winter will affect our lawns, so we will check back in later this winter with an update.
A historically warm, wet, and snowless December in Minnesota | MN Department of Natural Resources
It’s official: Minnesota, Twin Cities experienced the warmest December on record | St. Paul Pioneer Press
What does winter injury look like on your lawn? | UMN Extension
Research highlight
The University of Minnesota turfgrass team stays busy all winter with various projects aimed at learning more about how grass dies in the winter. While Minnesota residents with lawns might be somewhat worried about how their lawn is doing during the winter, professional turfgrass managers have much more to worry about. To read a perspective on winter stresses, both plant and human, read the following article by team member, and former golf course superintendent, Gary Deters.
Searching for a stress-less spring | UMN Turfgrass Science
Please note that we will be taking a short winter break in publishing this newsletter - watch for our next issue in March 2024!
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We provide research updates, lawn care tips, info about field days, and more at @UMNTurf.