Most are familiar with the benefits of mulching flowerbeds in the spring, not only to trap in moisture for the hot summer ahead, but also to minimize the proliferation of weeds. Winter mulching, though?
This practice is actually common among nurseries and gardeners in late fall to keep certain types of more delicate plants alive, but not necessarily to protect them from the cold directly. Landscaping mulch is only used to protect the most delicate plants from exposure to the cold.
More often, mulching is being used to protect the roots systems of younger bushes and saplings from shifting in the soil during repeated freezes and thaws, called heaving. Plants like ornamentals and perennials with weak root systems also benefit from the stabilizing but breathable cap. If the root systems of any of these young or less-hardy plants do shift from original positions, this leaves them especially vulnerable in future freezes and less likely to have a firm grasp on life in spring.
Just a few kinds of plants do need the extra coat for the winter, though. Roses need the extra coating of mulch up around their trunks in particular to ward off the cold. Exactly where the root trunk meets the first branches of a rose plant is called the graft union. When this area repeatedly freezes and thaws, that rose plant can die. Cover this area with extra insulation like composting material, leaf refuse or straw to ward off the cold. Do not, however, give other plants this up-the-trunk treatment.
Trunk systems on most perennials should be allowed to breath throughout the winter. They shouldn't have to deal with having a shelter for diseases, rodents or mold right on their doorstep. If you want to protect these plants, wrap them in blankets or sheets during especially cold snaps.
For plants like strawberries, it's next year's crop that farmers are protecting from the cold. The tiny buds of flowers, still tucked just below the surface, are coated with materials like straw or chips of bark or corn cob before the weather dips under 20 degrees Fahrenheit. As soon as spring breaks, the material is removed from the plants so as not to choke out any precious future strawberries.
Finding the right mulch depends on the type of plant being covered. Landscaping mulch that's made from wood chips, bark or even pine needles is usually used around larger bushes and to cover the root systems of trees and keep lawn equipment at a distance. Composting material or at least leaf matter should cover any wintering food gardens or beds of perennial plants in the winter. In spring, landscaping mulch can go on in heavier doses to seal in moisture and ward off some weeds.
Determining when to put on a bed of winter mulch is also important. Master gardeners recommend waiting until after a few bouts of frost. That way, perennials will have gone into dormancy first. Then, mulch can be applied to preserve some moisture and help to stabilize temperature shifts throughout the winter.
