This time of year, we all start thinking about how to best protect our landscape plants and trees from harsh winter temperatures.
During the spring and summer, we use mulch to keep weeds down and to keep the soil from drying too quickly. In winter, it’s a whole different story. Winter mulch is used to help maintain the temperature of the soil.
Note that I said maintain the temperature, not keep it from freezing.
The danger to perennials and landscape plants is from the alternate freezing and thawing of soil, which can result in heaving. Heaving is when the plant is pushed up and possibly even out of the soil because of temperature fluctuations. Small feeder roots can be broken during heaving, leaving the plant unable to absorb all the moisture it needs. Mulching around landscape plants after the plants have gone dormant and the soil is freezing helps to hold the soil temperature constant.
A common mistake is piling too much mulch around your plants, especially trees, creating a mulch “volcano.”
Woody shrubs and trees should not have mulch touching their trunks. During most seasons, this mulch keeps the trunk constantly moist, which can make it susceptible to disease. During the winter, this thick layer of mulch creates the perfect place for mice and voles to nibble on the outer layer of bark without being seen by predators. Since the nutrient and water needs of trees are met via the area of the tree just under the bark, this kind of girdling damage can easily kill a tree.
This is also the time when we need to take precautions against unwanted guests coming into our homes. I don’t mean that “favorite” family member that you have an obligation to entertain; I mean the mice that will be looking for a warm, cozy place to spend the winter.