If you think cleaning out the refrigerator is a scary task, wait until you see what waits for you out under the snow. Months after the first big dump, the white stuff continues to linger on the lawn, especially in shady, north-facing areas.
As a result, many Front Range lawns might see gray snow mold (Typhula incarnata), or its cousin, speckled snow mold (Typhula ishikariensis), cold-loving fungi that thrive in dark, damp conditions. When temperatures hover around freezing under snow cover lasting 40 to 60 days or longer, the fungus multiplies and spreads, feeding on the helpless leaves of grass. As the snow slowly melts, moldy patches appear, giving our lawns an unsavory just-spent-a-month-in-the-fridge look. Of the two fungi, speckled snow mold is the one producing the fuzzy growth on the grass; gray snow mold simply turns the blades brown.
Three types of snow mold can attack lawns after extended periods of snow cover, but none causes permanent damage. Not all lawns are getting moldy under the snow; only those that had this problem the last time we had extended snow cover.
“The way this fungus survives year to year is through sclerotia, small, hardened brown-to-black balls that wait in the lawn until the next time we have a snow that sticks around,” says Tamla Blunt, Plant Diagnostician with Colorado State University Plant Diagnostic Clinic in Fort Collins. “They look like pepper, so when you see grey moldy stuff growing on the lawn, check it to see if it looks like someone sprinkled pepper on it.”
The peppery-appearing sclerotia are tiny, says Blunt, so get up close and personal to see if your mold is covered with them. If the snow melts off, leaving brown patches without fuzz, suspect gray snow mold. As the lawn dries out, the fungus stops, leaving the turf to turn a light tan which fades to off-white. But if your lawn is growing more than grass, don’t panic.
“It’s really just a curiosity, not a problem for the lawn,” said Dr. Tony Koski, Turf Specialist with Colorado State University Extension. Snow mold, though it kills the grass blades, rarely kills the crown and your lawn should grow back healthy this spring.
But before spring arrives, give your grass an assist in getting rid of its fungal fuzz. Rake the grass, fluffing the blades and exposing the area to air and sunlight. In spring, give it a light application of nitrogen to boost its growth, especially if no winterizer fertilizer was put down last fall.
A third frigid fungus, pink snow mold (Microdochium nivale), appears later in spring when the weather is unsettled. The frosty nights and warm days with fog or irrigation are perfect for this disease. Pink snow mold first appears as water-soaked spots, rapidly growing to a foot or more in diameter with the pinkish border along outside edge. The spots often have a frogeye center of green, turning reddish brown to tan.
Treat pink snow mold as you would the others, and your lawn will rebound just in time for summer.
This post previously appeared in the Longmont Ledger.