What is Snow Mold?

Snow doesn’t always lead to snow mold, but this year’s heavy, lasting snowfall that started before the ground froze in many parts of the country means it will definitely be showing up in a lot of yards this year.

If you haven’t heard of snow mold, it’s a fungal disease that becomes visible in spring as the snow melts. There are a couple of different types of snow mold. Gray snow mold is caused by a fungus called Typhula blight, and pink snow mold is caused by the fungus Microdochium nivalis. The fungi overwinter in infected plant debris—though gray snow mold can also survive in the soil—and they start growing during the winter underneath their cover of snow.

You know you have snow mold when you see circular, beige-colored patches in your lawn in the spring. As long as the grass stays wet and cold, those patches will keep getting bigger. These patches will look matted and may have patches of fungal growth. Gray snow mold can be anywhere between white and gray and pink snow mold will be white to pink. You may even see some mushrooms popping up in spots.

Though it looks horrible, damage from snow mold is usually just temporary. Gray snow mold stops growing once temperatures reach 45°F or the soil surface dries out. Pink snow mold, though, may flare up in wet weather if temperatures are between 32°F and 60°F.

If you have snow mold in your lawn, rake the affected patches gently to help loosen up matted areas and promote drying. Those areas should green up fairly quickly as the weather warms up.