Snow Mold: What It Is & How to Treat It

Most signs of spring, like blooming flowers and warmer weather, are a welcome sight. But seeing odd, gray-colored circles on your lawn after the snow melts? Not so much. This is likely snow mold, a lawn disease caused by a cold-weather fungus that becomes noticeable once winter ends.

There are two types of snow mold: gray and pink. Pink snow mold (also called Microdochium patch or Fusarium patch) can cause more damage, as it can kill grass at the roots and crown, while gray snow mold (also called Typhula blight) usually only harms the grass blades. The good news is that with a little work in the fall, you can help prevent both types from showing up in the spring.

How to Identify Snow Mold

The signs of snow mold are most obvious in the spring right after the snow disappears. Here’s what to look for:

• Circular Patches: You’ll notice straw-colored, circular patches in the lawn that can range from a few inches to several feet across.
• Matted Grass: The grass inside these patches often looks crusty and matted down.
• Distinct Colors: The color of the patches can tell you which type of snow mold you have. They will have a grayish-white look if it’s gray snow mold, or a whitish-pink appearance if it’s pink snow mold.

What Causes Snow Mold?

Snow mold develops under the snow cover on your lawn. It becomes a major problem when a heavy, deep snowfall occurs before the ground has had a chance to freeze completely. This traps moisture on fragile grass plants. The problem is made worse when things like a thick layer of unraked leaves, long grass, or lawn debris are still on the lawn.

Grass Types Commonly Affected by Snow Mold

While most grasses are susceptible to snow mold, it is most common in cool-season grasses like:

• Bentgrass
• Kentucky Bluegrass
• Fescues
• Perennial Ryegrass

Need help identifying your grass type? Check out our article on Different Types of Grass.

Your Best Defense: How to Prevent Snow Mold

The key to dealing with snow mold is prevention, which means taking a few extra steps during your fall lawn care routine.

• Mow Before the First Snow: Long grass is a breeding ground for gray snow mold, so make your last mow of the season 1 to 1.5 inches shorter than usual, being careful not to scalp the lawn.
• Don't Let Leaves Pile Up: A thick mat of leaves creates a welcoming home for snow mold. Use your mower to mulch leaves into the lawn instead.
• Dethatch if Needed: A thick thatch layer also provides an ideal environment for snow mold. If your thatch is over ¾ of an inch thick, dethatch your lawn in the fall.
• Feed with the Right Fall Fertilizer: Too much readily-available nitrogen late in the season can encourage snow mold. Instead, use a slow-release formula like Scotts® Turf Builder® WinterGuard® Fall Lawn Food.
• Avoid Deep Snow Piles: When clearing driveways and sidewalks, try to avoid making deep snow piles on the lawn, as these take a long time to melt.
• Use a Preventative Fungicide: If you have had problems with snow mold year after year, apply Scotts® DiseaseEX™ Lawn Fungicide in the fall before the first heavy snowfall.

What to Do When Snow Mold Appears

If you find snow mold damage in the spring, it's important to know that fungicide treatments will not be effective. The best course of action is to gently rake the affected areas. This will loosen up any matted grass, helping the lawn dry out and giving healthy, unaffected grass blades room to grow.

How to Repair Your Lawn After Snow Mold

In some cases, the grass damaged by snow mold may not recover. If that happens, you’ll need to repair the spots. Once the weather permits, fix any damaged areas with a patching product like EZ Seed® Patch & Repair. Just choose the right product for your grass type and follow all directions on the label.

You don’t have to spend all winter worrying about what your lawn will look like in the spring. Follow these tips, and you can look forward to a lush, green lawn.