Every year some lawns develop snow mold. This week when I was outdoors, I saw snow mold in some yards here in Northern Colorado. From far away it looks like matted down grass, but a closer look shows a gray web-like substance on the grass. Up close it can look quite disturbing if you have not seen it before.
What causes snow mold? According to CSU Extension, “Snow mold is a fungal disease that develops when snow falls on unfrozen turf and remains there for long periods of time.” Two lawns I observed where the mold was present were North facing. North facing lawns have slower melt times than their neighbors across the street on the South side of the street which means the snow stays on that section much longer in comparison. This last storm came right after a warm spell which is the perfect condition for snow mold to present itself.
What can you do? We recommend removing large piles of snow by evenly distributing them to allow the snow to melt more quickly and the grass to dry out. When the grass dries the snow mold becomes cake-like and hardened. It is best to rake the grass to break the mold up. Spring aeration is also beneficial to break up the snow mold and allow nutrients to get to the roots. Areas affected by snow mold might take longer to green up in the spring. If the snow mold is severe, it can kill the grass. If snow mold consistently occurs in a lawn year after year, a preventative fungicide application in the fall is beneficial yet rarely required. The pictures I took below show a mild case of snow mold.
References: https://planttalk.colostate.edu/topics/insects-diseases/1400-15-snow-mold-lawns-colorado/
