Snow Mold: What It Is, How to Treat It, and Prevent It

What Is Snow Mold?

Snow mold is a fungal disease that commonly affects lawns in regions with heavy snowfall and cold winters. It becomes visible as snow melts in early spring, revealing circular patches of discolored or dead grass. These patches are typically straw-colored and can range from a few inches to over a foot in diameter. While snow mold can look alarming, it is generally not a lawn killer and can be managed with proper care.

The fungus responsible for snow mold lives in the soil year-round but only becomes active when temperatures are between 32 and 45 degrees Fahrenheit and moisture levels are high. This makes early spring, when snow is melting and the ground is still cold and wet, the perfect time for snow mold to thrive.

Types of Snow Mold

There are two main types of snow mold: gray snow mold (Typhula blight) and pink snow mold (Fusarium patch).

• Gray Snow Mold (Typhula blight): This type of mold is white to grayish-white in color and usually appears after the snow melts. It is less severe than pink snow mold and typically only affects the grass blades, not the roots. Gray snow mold requires snow cover to thrive.
• Pink Snow Mold (Fusarium patch): Pink snow mold is more severe and can affect both the grass blades and the roots. It appears as pinkish patches and can cause more significant damage to the lawn.

What Kinds of Grass Does Snow Mold Affect?

Snow mold can grow on any type of cool-season turfgrass that is covered by snow for long periods of time. However, certain grasses are more susceptible than others. According to the University of Illinois’ Integrated Pest Management Department, bentgrass is particularly susceptible to snow mold. Kentucky bluegrass, the most popular cool-season grass, is moderately affected, while fine fescue has more resistance to snow mold than other types.

Removing Snow Mold From Your Lawn

Once you see snow mold, the damage is already done. Applying fungicide at this point will not help. The most you can do is gently rake the area to loosen up any matted snow mold grass and allow the soil to dry more quickly.

As the weather warms up and the soil dries, you’ll have a better idea of how much grass has been affected. Gray snow mold doesn’t kill the roots, so your grass may bounce back from it. For areas affected by pink snow mold, rake away dead grass and re-seed bare patches.

How Do I Prevent Snow Mold From Growing?

The key to removing snow mold is to prevent it from growing in the first place. Here are some tips for preparing your lawn in the fall before the snow hits:

• Mow before the first snow: Cut the lawn slightly shorter than normal so that the grass and soil will trap less moisture. Also, consider bagging up your lawn clippings so that they don’t keep the ground damp.
• Apply a preventative fungicide: If you know your lawn is particularly susceptible to snow mold, treat it with a specialized product before the heavy snow sets in.
• Don’t fertilize in late fall: Cool-season grasses go dormant in the winter by letting grass blades dehydrate, making them less susceptible to mold. They will revive themselves naturally in the spring. Don’t interrupt this process by fertilizing within about six weeks of the first expected snowfall.
• Don’t let leaves or snow pile up: Anything that traps moisture is bad news for grass, so rake up leaf piles in the late fall. Similarly, when shoveling driveways or sidewalks, try not to create large piles of snow on the lawn that will take a long time to completely thaw.

Restoring Your Lawn

If you find yourself with snow mold in the spring, don’t worry—it will typically resolve itself as temperatures warm up. The snow mold fungus will stop growing when temperatures are between 45 and 60 degrees and the soil starts to dry out.

Until then, if you’re tired of seeing unsightly patches on your lawn, you can gently rake over those areas to dry them out more quickly. Apply new grass seed to repair those spots. Avoid adding fertilizers or fungicides at this point, as they won’t help and will only weaken your lawn as it’s attempting to heal itself.

FAQs About Snow Mold

How do you treat snow mold?

Snow mold typically does not require a fungicide treatment. If you gently rake the damaged area, the mold will often die off as the ground and grass dry out.

How bad is snow mold?

Damage from gray snow mold is typically not bad and only affects the blades, so the roots remain healthy. However, pink snow mold affects the grass roots, so the affected grass will likely die.

Where is snow mold found?

Snow mold is found in lawns in climates that receive moderate to heavy snowfall. It often occurs in areas of grass where snow is piled or naturally accumulates.

Additional Tips for Lawn Care

Here are some additional tips to keep your lawn healthy and prevent snow mold:

• Keep your lawn mowed to the appropriate height throughout the growing season.
• Aerate your lawn to improve soil drainage and reduce compaction.
• Water your lawn deeply but infrequently to encourage deep root growth.
• Remove thatch buildup to improve air circulation and reduce moisture retention.
• Consider overseeding with a more resistant grass variety if you have recurring snow mold issues.

Conclusion

Snow mold is a common issue for lawns in regions with heavy snowfall and cold winters. By understanding the causes, types, and prevention methods, you can keep your lawn healthy and vibrant. Remember, the best way to deal with snow mold is to prevent it from occurring in the first place. With proper care and attention, your lawn can recover and thrive each spring.