THE NOT-SO-NAKED TRUTH ABOUT WINTER MULCHING

Image Gallery Cold-weather mulching protects perennials in much the same way as a heavy blanket of snow insulates the ground in winter. Photograph By David Cavagnaro

SEASONS OF THE GARDEN

The answer to that eternal question: Should I mulch my perennial fruits?

By Stu Campbell

BY NOW, WITH ANY LUCK, YOUR RHODODENDRONS and azaleas are safely nestled under a layer of pine needles (or wood chips or sawdust or whatever), your roses are snug under their protective cones and are now mere drifts under a blanket of snow, and your bulbs have been tucked away before the first hard frost.

Now is the time to turn your attention to perennial fruits. There has been much controversy and confusion over the cold-weather mulching of these plants. Some say that a garden should be left naked and exposed for the winter. Authors John and Helen Philbrick have written, "Mulch should not be left on over the winter because it prevents the beneficial action of the frost in the earth. Moisture should not be hindered from 'coming and going' during seasons of snow and ice. If protective mulch is in such a condition that it will break down during the winter and become part of the topsoil, it may be left. But the home gardener should study this subject carefully and be sure he knows exactly what he is doing and why he is doing it."

I have made a study of this--a cursory one, at least. I asked the question, "Why does Mother Nature arrange to have her trees drop their leaves, and then see to it that a heavy blanket of snow insulates the ground even more? Is winter mulching, then, a bad thing?" I have concluded that your garden, particularly your perennials, should have winter mulch. But there is no rush to put it there.

Vermonters laugh unsympathetically at "down-country" people who bundle up under many layers of winter clothing in a futile effort to keep the cold out and keep their own body warmth in.

Winter mulch acts in the same way, except that it keeps winter soil frozen--even during thaws. Winter moisture and frost should be allowed to penetrate the soil before you lay down a heavy winter mulch. Then, if the mulch keeps the frost in, the plants cannot be "heaved" out of the ground when the soil expands and contracts on alternately freezing and thawing days.

Winter mulch protects perennial foliage from drying winds and too-bright winter sunshine. It prevents the absorption of heat in the spring and won't allow a thing to grow until after the last killing frost, when it is finally removed.

Last point of debate: How much winter mulch is enough? I suppose it's possible to smother plants under too much winter mulch. One approach to the problem might be to find out the average frost depth in your area from your local bureau of the National Weather Service. Then roughly estimate how deep your plants' roots are. Once you know this; you might find that Dr. D.E. Pfeiffer provides a clue. He says, "Winter mulch does the same thing that snow does: It insulates the soil to the same depth as the height of the mulch. If there is a three-foot snowfall, the effect of the snow reaches down to a depth of three feet. A mulch acts in the same way." This doesn't mean that you have to mulch to a level equivalent to the bottom of the frost level. That would mean as much as four feet of mulch in Vermont! It only means that you should mulch to a height that is a little greater than your perennial plants' roots are deep--that is, if the frost level where you live goes below that point.