What You Need to Know About Mulch
The biggest benefit of winter mulch is that it helps to moderate soil temperatures. Rather than thawing and then re-freezing every time there's a sunny winter day, soil that's covered with a layer of mulch will usually stay a relatively consistent temperature. This helps keep your plants fully dormant until spring arrives, and also minimizes damage to the roots that can be caused by frost heaving.
If you have dependable snow cover from December through March, you probably don't need to mulch. But these days, even in the coldest parts of the country, that's rarely the case.
Which plants should be mulched? The amount of mulching you do in your own garden depends on the severity of your climate, the condition of your soil, the kinds of plants you have, the amount of mulch materials you have on hand, and how much time you can devote to the task. Remember that in most cases, winter mulching (like cutting back your perennials) is one of those good but not essential tasks. If you can't mulch everything, concentrate on plants that may be marginally hardy or those that you especially treasure.
When to mulch: If you do mulch, don't rush it. Plants should enter winter dormancy slowly and completely. For this reason, mulches should be applied only after the ground has frozen, which in many areas will be around Thanksgiving or the first week of December. Once the ground begins to thaw next spring, it's important to pull the mulch several inches from the crowns of your plants. This will give newly emerging growth access to sun and good air circulation.
What to use for mulch: An effective winter mulch must be water- and air-permeable so as not to smother the plant below. Non-matting winter mulch materials include: shredded leaves, evergreen boughs, pine needles, salt hay, weed-free straw, chopped cornstalks, wood shavings and compost. Do not use whole leaves; they pack down and can suffocate the plant they're intended to protect. For most plants, 4 to 6 inches of mulch is adequate. Roses should have a full 10 to 12 inches of soil or compost mounded up over the crown of the plant.
In exposed areas, you can use garden fabric or burlap to hold organic mulches in place.
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