Snow Mold and Turf

Josh Cornell, Horticulturist, The Gardens on Spring Creek

Colorado weather is anything but predictable, which can make lawn care challenging.  With more snow in the forecast ahead, you may end up experiencing some snow mold on your grass. 

Snow mold is caused by cold-weather fungi that primarily affects grasses.  While we don’t usually see this problem in our arid western climate, it occasionally happens, especially when the snow lingers.  This provides the perfect conditions for snow mold, which, if allowed to persist, can cause damage and even kill the crowns of grass plants.

There are two types of snow mold: gray (Typhula blight) and pink (Microdochium or Fusarium patch).  Both types become noticeable in the spring when the snow melts, leaving circular patches of matted or crusty grass that range in size across the lawn.  With gray snow bold, these patches are generally grayish-white in color, whereas pink snow mold causes whitish-pink patches.  Additionally, gray snow mold usually only affects grass plants’ blades, while pink snow mold can be more severe, killing the crown and the roots.

Prevention:  To prevent snow mold, clean up your turf areas in the fall.  Snow mold thrives when snow sits on turf for an extended period of time, especially in areas matted with tall grass, leaves, and detritus where moisture can be trapped.  Also, try to mow your lawn a bit shorter for the last mow of the season, before any snow comes to stay. If you have an area where you have experienced snow mold repeatedly, you can apply a preventative fungicide in the fall as well.

Reaction:  If you find that you have snow mold, the best thing to do is to rake out the affected area. This will do two things, provide airflow and remove any debris that could be harboring the mold. Sunlight and higher temperatures, along with Colorado’s dry air, are detrimental to snow mold.  After treating your lawn for mold, you may notice spots that have died.  Fill these areas in by reseeding with a product that matches your turf.