March — Snow Mold

by Tom Lewanski

In the month of March, in the great state of Minnesota, we gain something like 21 hours of daylight. Okay, this is probably an exaggeration. After consulting and studying the sunrise and sunset tables for the March 1 and 31, and trying to figure in the ‘spring ahead’ effect of daylight savings time, honestly I just gave up. I’m not getting any younger here. For those of you bent on rigorous scientific study, how about we compromise and just call it a lot more daylight?

One effect of all this additional sunshine is that temperatures begin to rise. You heard it here first. While I have not seen any specific research to back up this claim, a rise in temperature typically results in a decreasing snowmass. If you’re like me, you can’t wait until the snow melts down to the herbaceous, or soil, layer. It’s like lifting a cover off the world; what’s been going on under there for the last couple of months?

In my yard, as the snow melts, the tunnels that meadow voles have been using to get at seed that has been dropped from the bird feeders are exposed. Another subnivian phenomenon that we may begin to see evidence of is snow mold. Yep, snow mold. Now, most micro-organisms don’t do so well in cold temperatures. Frankly, it’s just too darn cold. Not so for the snow molds. They thrive at temperatures around 0° C.

There are two types of snow mold, gray and pink. These fungi grow on dormant plants under snow cover. The ideal conditions for these fungi are provided during winters when there’s an early and persistent snow cover, which prevents the ground from freezing. Gray snow mold stops growing when temperatures go above 45ºF. The snow cover provides the low temperatures and high humidity these molds thrive on. Because there are few, if any, competitors active under these conditions, the snow molds can go nuts. Ingenious.

What do they look like? If your lawn is being affected by snow mold you will see circular, straw colored patches when the snow melts away. The grass within these areas has a matted look and there will be colored fungal growth. Yes, you guessed it, gray snow mold will be whitish/grayish while the pink snow mold will be white to pink.

Great, just great! Now we have something else to add to our worries list. The reading I have done on this subject, which has certainly not been exhaustive, seems to indicate these molds rarely cause serious damage to our lawns. Usually the aforementioned patches are a little slower in greening up then the rest of the lawn. Rake the area to raise the nap, which will help the area to dry. Snow mold, who knew?

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