If you live in an area with heavy snowfall you might have noticed a really curious thing in the spring. When the snow melts your lawn is covered in what looks like tiny fine spider webs. But it’s not webbing, it’s mold! Here’s what to do.
It’s certainly a curious sight. The snow begins to recede, the grass is still dormant, and where the snow was mere days before there are sprawling “webs” all over your lawn. It looks so much like cobwebs or the fine webbing tent caterpillars make that you’d certainly be forgiven for thinking some cold-hardy industrious bug had been hard at work under the snow. But the fine whispy structures aren’t the results of bugs but fungi.
What Is Snow Mold?
Snow mold is a type of fungus that thrives in the cold damp conditions found in your lawn after the snow melts. There are two types of snow mold caused by two different kinds of fungi. Here’s a breakdown of the types and how to identify them.
Typhula Blight
The first kind is Typhula blight, named such because it is caused by fungi in the Typhula genus. You’ll also hear it, more commonly, called gray snow mold or speckled snow mold on account of its light greyish-white coloration.
While this kind of snow mold can thrive anywhere the conditions are right, it’s particularly common in the Great Lakes region and the North East areas of the United States as the combination of long cold winters and damp cold spring weather offer ideal conditions.
Key Identifiers: Greyish coloration. Can be distinctly circular or more of a sprawling general “blanket” pattern. Sometimes has distinct edges, but is often just uniformly a dusty white-grey color over the entire area.
Fusarium Patch
The second kind of snow mold is Fusarium patch—also called Microduchium patch or pink snow mold—is caused by the fungi Microdochium nivale. Although the edges of active infections can appear similar in appearance to Typhula blight, it has a faint pink/red tinge that stands out compared to the grey dusty look of Typhula blight and it has a much more distinct circular appearance.
Though snow cover helps Fusarium patch thrive, it merely needs sufficiently cold and damp conditions to grow. Areas that experience winter dampness with cold but not freezing weather are prone to Fusarium patch because it thrives in temperatures between 32-46°F. So even if you live somewhere without significant snowfall, or snow at all, you can still get this “snow” mold.
Key Identifiers: Pronounced pinkish-red color. Has a distinctive circular pattern but multiple infections may merge together to create patterns that look like soap bubble chains. The center of the circles is typically dead grass with a very visible edge reminiscent of a ringworm infection.
Does Snow Mold Hurt My Lawn?
Both kinds of snow mold can damage your lawn, especially if left unchecked over time. Unless you’re running a golf course that needs to be in absolutely tip-top shape before the season starts, there’s no need to panic.
Typhula blight is the least damaging kind of snow mold. Typically the situation will simply resolve itself as the weather warms. In most cases any discoloration or damage to the lawn is superficial and the turfgrass will recover quickly, growing new blades into any patches that formed. In more severe cases the mold covers enough of the lawn that the lawn is slow to recover and fill in. You may need to reseed the area in such instances.
Fusarium patch, on the other hand, can be more problematic. Unlike Typhula blight it doesn’t just damage the blades, it can infect the crown and roots of the grass and kill the grass completely. The result isn’t just a little discoloration of the blades that resolves quickly during the start of the growing season, but distinct straw-like dead patches that have the appearance of grass burned out by intense summer heat.
How Do I Remove Snow Mold?
If you found this article because there are odd spidery-web patches on your lawn, you’re technically in the too-late phase of dealing with snow mold—for this year at least. The mold spores were there last fall and now you’re seeing the effects of the mold entering its growing season.
That said you’re not totally helpless in the face of the mold. At this stage, there are a few things you can do to help hasten the recovery process.
- Gently shovel any residual piles of snow, such as those next to your sidewalks, onto the street or your driveway to melt them off and to expose the grass to the open air.
- Very lightly rake the lawn to both break up the snow mold and remove any debris like old leaves you missed in the fall.
Both of these actions will help your lawn dry out faster. Between the lowered humidity and the sun exposure, the mold will die back quickly.
How Do I Prevent Snow Mold?
While it’s too late to prevent snow mold in the spring once you’ve already discovered it sprawled across your lawn, it’s not too late to set up a plan for preventing it next year. Let’s take a look at three ways to prevent snow mold.
Apply Fungicide
Naturally, one of the most potent tools you can use to stop snow mold from forming is the application of a fungicide.
Fungicides are of no use once the infestation is visible in the spring, but if you apply them late in the fall season before the first snowfall they are quite effective. For folks in the U.S., the application window is roughly around Thanksgiving each year.
Scotts DiseaseEx Lawn Fungicide
This granular formulation is effective against not just snow molds, but a wide variety of fungal problems that plague lawns.
You can have a lawn care professional apply the fungicide as part of other routine care, but it’s not difficult to do it yourself. Fungicides can be applied just like you would apply fertilizer. You can use a granular form with a broadcast spreader or hand spreader. You can also spray them onto your lawn with your hose fitted with spray bottle or you can dilute a concentrate and use a pump sprayer.
Using a hose sprayer is convenient for smaller lawns and a pump sprayer works well enough for small areas, but once you get above a few thousand square feet of lawn space to deal with it’s a lot more practical to use a fertilizer spreader.
Use Good Lawn Management Practices
Good lawn management and a few practical tricks can go a long way towards controlling snow mold. In fact, in many cases, you can skip the fungicide if you’re really proactive with your lawn care. The best part about this approach is that if you follow along with it the benefits are greater than just dealing with snow mold, it’ll make your lawn healthier in general.
- Don’t fertilize late in the season. Not only will letting your grass go dormant properly help protect it, but excess nitrogen levels give the fungi needed nutrients at a time when your lawn doesn’t need it.
- Address drainage issues. If areas of your lawn are perpetually damp because of poor drainage, those areas will be much more prone to snow mold.
- Give your lawn a tight mow right before the snow comes to help keep the soil drier during the dormant season.
- Minimize the organic materials on the lawn by bagging your last mow of the season and removing all the leaves thoroughly.
- Speaking of organic material, stay on top of lawn detaching so the snow mold doesn’t have a ready “matrix” of dead organic material to grow on.
- Try to minimize excess snow buildup, especially near driveways or sidewalks.
The impact of that last point is really interesting. Piling up snow from shoveling your driveway and sidewalks has a significant effect on snow mold development.
For example, I’ve never had snow mold in my backyard, despite living in an area prone to it. I do, however, get patches of Typhula blight in my front yard, but only in areas like the curb lawn and along the sidewalks where the snow is piled up deep, heavy, and wet as a result of shoveling.
If you can keep the snow from piling up like that you can oftentimes prevent the snow mold from forming. And if you live on a small city lot where there’s nowhere to put the snow you have to shovel, it’s worth treating that area with fungicide in the fall.
Seed with Mold-Resistant Grasses
We saved this method for last because for the majority of people it’s pretty impractical. If you’re planning a new lawn or rebooting your old lawn with a complete reseed, this method is worth considering. For folks with an established lawn, however, pulling out the nuclear option to deal with the minor inconvenience of snow mold is overkill.
While all cool-weather grasses are susceptible to snow molds, some are hardier than others. If you are planning a lawn or selecting a seed to overseed with this year, it’s worth considering snow-mold-resistant varieties of grass.
Bentgrasses and bluegrasses are the most susceptible to snow molds, while finer-bladed grasses such as fescues are more resistant. Consult with a local professional or your regional university extension office to find the best fit for your area.
But again, unless you’re starting from scratch opting to redo your lawn over mold is excessive and we recommend trying the management tips outlined above to deal with light mold issues and applying a fungicide if that doesn’t help.
So there you have it! There’s no secret infestation of arctic-hardy spiders under your lawn. That weird wispy network of webs is just a type of fungi—and with a little preventative maintenance, you can take care of it.