Snow mold is caused by cold-weather fungi that develop beneath extended snow cover, especially when grass is left long or covered with fallen leaves and debris. There are two main types of snow mold that may appear in spring. Gray snow mold, also known as Typhula blight, leaves grayish-white circular patches of matted grass and usually affects only the grass blades. If snow mold appears in spring, recovery is often straightforward. Get Northern Colorado’s top stories, weather, and events every day at 5 a.m. in our Daily Update.