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Spread out large snow piles to help avoid 'snow mold'

The deep snows last winter gave way to fuzzy white lawns in the early spring. Snow mold was abundant, and many homeowners asked what they could do about it. The answer is: Prepare for the reduction of snow mold in the fall.

Snow mold is common during years when an early, deep snow prevents the ground from freezing. The fungi that cause snow mold become active at temperatures near freezing. When the snow melts in the spring, matted gray patches of dead grass appear. Snow mold infects home lawns as long as conditions are cool and wet. Once temperatures begin to rise, and the lawns begin to dry, snow mold fungi become inactive.

The damage from snow mold is seldom serious. Generally, infected areas are just a little slower to green up.

To avoid the ghastly gray cast to your lawn next spring, take the following steps now:

• Avoid excessive applications of nitrogen fertilizer in the fall. The best time to fertilize your lawn is around Labor Day. Recent research out of the University of Minnesota has called into question the usefulness of a late October, early November fertilizer application. If your lawn is particularly susceptible to snow mold, skip fall fertilization altogether.

• Continue to mow your lawn at the recommended height until it is dormant. The taller the grass, the more likely it is to mat and encourage snow mold growth. However, do not cut your grass shorter than two inches. Grass cut this short is subject to winter injury in the event of a cold winter with little snowfall.

Rake up your leaves! Small amounts of leaves can be sufficiently ground up by the mower. Visible clumps of leaves, whether they've been chopped by the mower or not, should be removed, and composted or used as mulch around trees or perennial beds. A heavy layer of leaves left on your lawn creates the ideal environment for spring snow mold growth. A thick layer of leaves left to overwinter on your lawn can also result in dieback and thinning of grass plants.

A deep thatch layer can also contribute to snow mold growth. If you have a thatch layer of more than one-half inch, dethatch your lawn.

During the winter, spread out large snow piles to encourage rapid melting. Snow fencing can be used to minimize excessive snow accumulation in problem spots.

Even with all these precautions, snow mold will be more severe in those years in which an early snow falls on unfrozen ground.

For more information about snow mold, visit the U of M Extension website at:

Until next time, happy gardening!

"I prefer winter and fall, when you feel the bone structure of the landscape - the loneliness of it, the dead feeling of winter. Something waits beneath it, the whole story doesn't show."

- Andrew Wyeth