Snow mold is a disease caused by a fungus that appears in the early spring after the snow melts. Snow molds become active under the cover of snow during the winter. There are two kinds of snow mold, gray (typhula blight) and pink (fusarium patch).

Snow mold can grow at temperatures slightly below freezing and continues to grow in wet, cool grasses after the snow melts. Snow mold does grow under snow, but only on top of unfrozen ground, so areas where the ground freezes in the winter are not going to have snow mold. If fall and spring are wet and cool, snow mold will continue to thrive.

Snow mold looks like straw colored, circular patches. The patches grow during the wet, cold weather after the snow melts. You will be able to see fungal growth in the patch, either gray or pink depending on the kind of mold you've got. Sometimes the mold will produce mushrooms.

Preventing Snow Mold

To avoid snow mold, don't apply excessive amounts of nitrogen fertilizer in the fall. This feeds the snow mold. Snow mold also likes tall grasses, so keep mowing the grass until it completely stops growing for the winter. Piles of leaves are great places for snow mold to live, so rake up any fallen leaves before the first snow. Basically, you need to avoid giving the snow mold a place to grow, so try to keep everything trimmed, pruned, raked and generally neat.