I was actually going to title this post Snow Mold: Something to Sneeze At! Or maybe Snow Mold: Gack! What’s that Unsightly Stuff on My Lawn? Way more dramatic and punchy, LOL.
I’ve been hearing over and over again how snow mold isn’t a “thing” outside of Canada (or even western Canada; I saw a comment on social media from someone in Ontario who had never heard of the stuff and I know they get snow there). It’s quite possible that we’re more inclined to get it on the Prairies, as our winter conditions tend to support it more than elsewhere. It’s not unusual to see the arrival of the white stuff before the ground is completely frozen, and then to have large accumulations linger throughout the entire winter. This year, in Calgary (and it sounds like, in the rest of the province as well), we are having one big crazy snow mold party…it is everywhere! Yay! Achoo!
There are two main types of fungi that cause snow mold – gray mold is attributed to Typula spp. while Microdochium nivalis is responsible for pink mold. You’ll instantly recognize snow mold because it flattens the grass and leaves a sort of pasty grey-white or pink-white webbing on top. (You can see some good photos of it in this article). And you’ll also recognize that “snow” mold is a bit of a silly name, because the snow itself doesn’t actually mold. It just acts as a cover for the fungal activity.
In the summer the fungi loll around and do absolutely nothing. Although the heat doesn’t faze them, they are cold-lovers and when winter arrives, they get happy and start to grow. After the big melt in spring, you’ll notice them clumping all your turfgrass together and looking mighty pleased with themselves. And if you have seasonal allergies, boy, are you in for it. Next to pollen, snow mold has got to be one of the worst triggers (just ask me, I know all about it).
So, will this icky grossness do permanent damage to my lawn? Not usually. Severe infestations will cause patchiness, which can be easily remedied by overseeding. To deal with snow mold, you can rake it really gently when the ground is dry enough to do so. (If you have allergies, get someone else to do this job for you). “Gently” is the operative word, here, as you’ll yank up your grass if you rake too hard this early in the season. Bag up the clippings. Don’t thatch until later on, after the ground is completely thawed – this initial period right after melt isn’t the time to get aggressive with your lawn, as you’ll only do damage. You can also choose to do nothing: as the grass dries out and the temperatures increase, the mold will become inactive again, and greening will happen on schedule. A good soaking rain will also help wash away the problem. Don’t fertilize immediately after thaw, and don’t mow the lawn right away, either – wait until things dry up a bit.
Yes, snow mold will come back, and no, you can’t really do a lot to prevent it. Rake up your leaves in the fall, and don’t use a high nitrogen fertilizer late in the season. Give your lawn that final mow before the snow flies (if the precipitation doesn’t take you by surprise) – a shorter cut will also help deter voles, as well.
Burke, Kelly. “Identifying and Controlling Snow Mold in Your Lawn.” The Spruce. February 2, 2020. https://www.thespruce.com/snow-mold-2153094