Snow Mold Can Ruin Your Lawn’s Look—But It’s Easy to Prevent

Snow mold looks about as bad as it sounds: Basically, once snow and ice melt on your lawn, you're left with gray, matted grass patches that may later die and need to be filled in. The good news is that snow mold is easy to treat and won't cause any longterm damage to your lawn, but still, it's a temporary eye sore. If you're looking to prevent it, here's what you need to know. Thankfully, it doesn't take much besides some timely mowing, proper fertilization, and raking.

What Causes Snow Mold?

Snow mold is not a single disease but an umbrella term for up to four different types of fungi, including pink and gray snow mold. But what these organisms have in common is that they thrive in low-temperature, high-moisture environments. 

This is why those last piles of snow that remain on your lawn, sometimes even through the first weeks of spring, will sometimes reveal snow mold patches. Under them, the temperature remains low for long periods of time, and the thawing snow keeps both blades and soil continuously wet, making it a fungal paradise. 

How to Prevent Snow Mold

When it comes to snow mold prevention, wet and cold are your enemies. What you want is to provide the best possible ventilation conditions, so that turfgrass has a chance dry up if at all possible. 

But growing things is a long-haul game, so snow mold prevention doesn’t start in the winter, but rather in the middle of fall. 

Right before your grass goes dormant for the winter, give it a light nitrogen-rich fertilization to keep it strong through the colder months. However, Angela Madeiras, a plant pathologist and diagnostician at the Extension Plant Diagnostic Lab at the University of Massachusetts Amherst, is adamant that you carefully follow the instructions in whatever product you’re using to make sure you’re not going overboard.

“People tend to think that more is better and it's not,” she says. “You only have to have a certain amount of fertilizer, and putting more on than the recommended amount is not going to be better. In fact, it's going to cause more problems than it solves.”

Nitrogen-rich fertilizers are designed to boost leaf growth, which is something you don’t particularly want too much of when trying to prevent snow mold, says Kelly Kopp, extension water conservation and turfgrass specialist and professor in the plants, soils, and climate department at Utah State University. 

“What happens when you over-fertilize turfgrasses is they put the energy that they develop from that nutrition into creating more leaf growth,” she explains. “So, it's really how that increased leaf growth and density affects the moisture in that canopy.” 

Kopp mentions that grass blades have a lot of moisture in and of themselves, but when you have snow falling on that extra growth, the leaves will flop over and start to decompose.

Related: When to Fertilize Your Lawn After a Brutal Winter—Timing Is Everything

“You've just got a whole lot of leaf tissue that is creating more moisture there, which can facilitate the fungi's growth,” she adds. 

But controlled fertilization is next to nothing if you don’t combine it with some good ol’ mowing. After fertilizing your lawn for the last time in the fall, keep mowing it regularly and keep it really short until it stops growing—a telltale sign that your lawn has gone dormant. Shorter grass blades are less likely to tangle and provide a hospitable environment for snow mold proliferation. 

Additionally, short turf will have better ventilation, so whatever moisture falls onto your lawn will evaporate more easily with a sparser canopy. 

In the same vein, raking your lawn regularly to remove thatch, grass cuttings, leaves, and anything that might prevent it from being as dry as possible during the fall and winter, will go a really long way. 

Once the snow falls, your mission will be to give your lawn the best chance at drying possible. 

“There can be areas where people pile snow or where it accumulates more than others,” Kopp explains. “One of the really simple things that you can do is get rid of that or spread it out so that it's not just a huge, big pile of snow sitting in the same place for a really long period of time.”

Related: The Strange Lawn Disease That Shows Up After Snow Melts

When to Use Fungicide for Snow Mold Treatment

Neither Kopp nor Madeiras recommends using fungicides to treat snow mold in a residential setting, opting instead for cultural management practices. 

However, the Utah State University expert says that if you have a really severe, recurrent snow mold problem, a fungicide might be a good option. Just keep in mind that these chemicals are preventive treatments and should be used in the fall before the first snowfall, and your turfgrass goes dormant. Otherwise, the leaves won’t absorb the product, which will wash away with irrigation. 

“You really have to follow carefully the label on any product you're going to use like that, because there's great guidance on timing of application, rates of application,” she warns. “Those labels on things like fungicides and pesticides are considered legal documents, and you're meant to follow them as a law.” 

She clarifies that following instructions carefully when using these chemicals is crucial, as it’s the only way to keep everyone and the environment safe. 

“It's also to help people use these products in a way that they are very effective,” she adds. “Just because a little is good does not mean a lot is better.”