Snow Mold

Although snow mold can look scary, there’s actually some pretty simple ways to prevent it and treat it.

For the most part, a light covering of snow over your cool season lawn is actually beneficial during the winter months. The snow cover protects the lawn from drying out due to wind. It also helps insulate the soil from extreme cold temperatures, and provides valuable moisture to the roots in early spring when soil temps begin to warm. Despite it’s benefits though, snow cover does pose a small issue. It blocks air flow, and whenever you block air flow in your lawn it can create fungus issues. In this case, that fungus is Snow Mold. 

What is Snow Mold

Snow Mold is a fungus that effects cool season grasses. There are two types, Gray Snow Mold and Pink Snow Mold. For the most part, as a homeowner you’re more likely to encounter Gray Snow Mold, which is less damaging.  Pink snow mold, which is typically found in golf courses where there is bentgrass, is more likely to cause irreparable damage since it can damage the roots, and crown of the grass.

Usually, fungus issues are more of a mid summer problem, but with snow mold it’s actually the cooler soil temps, matched with increased moisture and decreased air flow due to snow cover that trigger the flare up of the fungus. The fungi are most likely in your soil all year and only become a problem when conditions become ideal. 

What Does Snow Mold Look Like

Snow mold will become noticeable in late winter/early spring when snow melts and your lawn becomes exposed. With Gray Snow Mold, you’ll notice gray or white circular patterns that can combine to leave large patchy sections. You’ll probably notice in these areas the grass is matted down. Also in infected areas, you may see what appears to be spider webs (see pic below). This is called mycelium or ‘fungal webbing’ and it has nothing to do with spiders. It’s actually the vegetative part of a fungus that uses this web like branching system to transfer water and nutrients. 

Pink Snow Mold looks very similar but as the name implies it usually appears more pink. You’re more likely to identify Pink Snow Mold later in the spring since infected areas may continue to be brown as the rest of your lawn greens up. With Gray Snow Mold on the other hand the infected areas are very likely to recover and green up with the rest of your lawn. 

But once again, the typical homeowner is more likely to have the less problematic Gray Snow Mold. 

Treatment

It sounds really simple, but the best thing you can do if you have snow mold is to gently rake matted down sections of grass to increase air flow to the soil. This can be done in early spring when snow has melted and your soil is no longer frozen. At this point your lawn should be starting to come out of dormancy. 

Don’t use a metal garden rake for the job, instead use a light spring rake (metal or plastic) and just make a couple of passes over the area to prop up the matted down grass.

As the rest of your lawn starts to wake up you should notice the infected areas start to green up as well. It won’t take long for the snow mold to disappear.

In the unlikely event you have permanent damage from Pink Snow Mold than repair damaged areas by top dressing with a little compost or peat moss and apply seed. You’ll also need to tweak your lawn care program by avoiding pre emergent herbicides if doing any seeding in the spring. 

Prevention

– Cut low for the last mow of the season. When your grass is done growing for the year and it’s time for one last mow, drop the cutting height at least a notch or two. During the fall you should be gradually decreasing your mowing height. When it’s time for the last cut of the season bump it down even further, but not so low that it scalps the lawn. Mowing low will help keep grass standing tall instead of flopping over when it snows. 

– Collect leaf litter and clippings. Remember, you want to do everything possible to not smother your lawn before the snow flies. Rake or suck up leaves, and if you can bag the last mow of the season than definitely do it. Clippings and leaves won’t have time to break down before the snow comes. Leaving them on your lawn at the end of the season will have the same negative effects as matted down grass. 

– Remove thatch. If you have a thatch problem heading into winter, there’s no doubt it’ll increase your odds of getting snow mold. Tine rake dethatching, or power raking may be necessary depending on the type of thatch problem you have. For everything you need to know about thatch check out: Lawn Dethatching 

– Apply high nitrogen fertilizer, late in the season. Many people refer to this as a Winterizer. Applying a high nitrogen, quick release fertilizer at the end of the season will help your lawn recover from snow mold in early spring. Your lawn will store the nitrogen and use it in the spring when soil temps increase. 

– Apply a preventative fungicide. Applying liquid Propicanozole at a rate of 3 ounces per 1000s/f before the snow falls will help prevent snow mold. Personally, I would only recommend this if you are concerned with Pink Snow Mold. If you’re near a golf course or have bentgrass than this may be worth it for you. Otherwise, since fungicides can be expensive you may want to consider this as a last resort, especially for Gray Snow Mold since your lawn is very likely to recover from it.

–Avoid snow piles. I know it’s hard to avoid, but under large piles of snow is most likely where you’ll see problem areas. Heavy snow piles cause grass to flop over and they also stay on the grass longer since it takes longer to melt in the spring. If snow plowing or shoveling, try and use non lawn areas for piling snow as much as possible.

Check Out These Posts Next

Treating and Preventing Lawn Fungus

Summer Lawn Care

3 Product Lawn Care Program- Cool Season Lawns

Lawn Care Program for Warm Season Lawns

Dormant Grass

Winterizer Fertilizer: Everything You Need to Know

Top Dressing Lawn: Benefits and Advice

Core Aeration and Overseeding

How to Fertilize Your Lawn

Lawn Dethatching: Everything You Need to Know

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