There are two types of Snow Molds, Gray and Pink snow mold. Both types of snow mold become active underneath extended periods of snow cover. Snow mold develops on top of the lawn, between the grass and the snow. Snow mold tends to occur after a winter of prolonged period of snow where the snow did not completely melt for many weeks.
After the snow finally melts, there is a noticeable patchy or blotchy cottony-type webbing that is resting on top of the grass. This is snow mold and it will die quickly after it is exposed to warmer temperatures and sunlight. The snow mold does not damage the lawn, but if the snow mold is left to sit on top of the grass it will block the sunlight from reaching the blades of grass. This will prevent the grass from producing chlorophyll. Unfortunately, the damage to the lawn does not appear until a few months later when parts of the lawn are not greening-up properly.
Gray Snow Mold also called Typhula blight, is active in lawns at temperatures just above freezing. Circular patches (6-12 inches) will have a moldy appearance when fungus is actively growing. The active snow mold can be seen immediately after the snow melts.
Under severe conditions, these smaller patches may grow together to form large, matted areas that appear to be dead. As the lawn begins to dry out the fungal growth slows. Patches can take on a light tan appearance, fading to light gray or white.
Contrary to popular belief, late-season fertilization (also referred to as “fall” or “winterizer” fertilization) neither encourages snow mold nor increases its severity. In fact, late-season/fall fertilization will encourage more rapid healing and recovery in lawns if they become afflicted with snow mold damage.
Gray snow mold can be seen after the snow melts in a lawn. This is seen after the lawn has had a long period of snow coverage.
Snow mold will die very quickly when exposed to sunlight or the area dries out. Gray snow mold activity stops when the surface dries out or the temperature exceeds 45° F. Pink snow mold activity may continue during wet weather in the fall and spring, as long as the temperature is between 32° F and 60° F. Gray snow mold is common in Colorado and pink snow mold is not very commonly found in Colorado lawns.
Symptoms of the snow mold damage appear in the lawn long after the snow mold is no longer active. Most homeowners notice the snow mold damage as circular, straw colored patches of lawn that are surrounded by green grass. The damaged areas often have a matted appearance and discoloration.
The damage caused by snow mold is seldom serious. If the snow mold is minor the infected areas will be slower to green-up compared to the other parts of the lawn. The snow mold dies and sits on top of the grass. The dead mold blocks the sunlight from reaching the turfgrass, preventing it from producing chlorophyll.
To cure and prevent snow mold damage the homeowner should gently rake the affected areas of the lawn with a leaf rake. The raking breaks up the snow mold allowing sunlight to reach the grass. The lawn will begin to green-up within a few weeks after the snow mold has been broken up or removed from the top of the grass.
In severe cases the snow mold can cause major damage. This only occurs if the snow mold is not broken-up or removed. If the snow mold is left on top of the lawn for too long then the grass can die. In severe cases where permanent damage does occur, a top seeding package may be required to repair the damaged lawn. Fungicide applications are unnecessary because they will not prevent damage to the grass. Breaking up the snow mold is the only effective way to prevent damage to the grass.
Damage from snow mold tends to be on the north side of properties or in areas where the lawn does not get a lot of direct sunlight. Although it is possible in a very snowy and cold winter, south facing slopes usually do not suffer from snow mold damage.
If your believe your lawn is damaged from snow mold and needs to be repaired please contact Organo-Lawn in Boulder (303) 499-2000 or Fort Collins (970) 225-9425 and schedule a disease diagnosis with one of our professional lawn care technicians.
Click on an image below to enlarge the picture
This is what snow mold looks like when it is still alive and growing.
This is grey snow mold in a lawn. It looks like cotton and has a sticky feel to the touch.
The brown spots in this lawn are where snow mold was covering the grass.
Snow mold damage is usually not noticed by a homeowner until a few months after the snow melts.
Gray snow mold damage on grass a few weeks after the snow mold died.
This is a close up of what snow mold looks like on grass a few weeks after it has died.
Snow mold does not damage the grass; however, it prevents the sunlight from reaching the blades of grass. Snow mold damage is easily prevented if the lawn is raked lightly, with a leaf rake, to break up the snow mold that was sitting on top of the grass. Snow mold damage is usually only noticed by an untrained eye after the lawn begins to green up for the season. The areas that the snow mold was sitting on top of the grass will remain brown while the other areas of the lawn will turn green.