It's the cold season, and mice have been seeking bed and board, which is not good for our plants. You may already have seen evidence of their gnawing at the base of some small tree.
Mostly, it is meadow mice - also known as meadow voles or field mice - that do damage. They're most at home in tall grass where they can feed, nest and scamper about, shielded from the eyes of hungry hawks, owls and other predators. Unfortunately, from fall to spring, meadow mice like to supplement their diet of grasses and herbs with the bark of trees.
The first line of defense is to make your yard inhospitable to meadow mice by mowing your lawn as late and as closely as possible. A few mice still will be brave enough to scoot across your mowed DMZ, so further protection is needed, at least for young trees that mice find most appealing.
Cylinders of quarter-inch mesh hardware cloth, paper wraps or plastic tree guards provide good protection. Mice are vegetarians, so they also are repelled from bark painted with a diluted mixture of white latex paint and bone meal.
Thwarting bark-eating mice does not stop there. Straw, leaves and other organic mulches are beneficial for the soil and for plants but also provide cozy lodging for mice. So hold off spreading these mulches until mice have found other places in which to settle for the winter. And never pile any mulch right up against a tree's trunk, or you'll give mice easy food and lodging.
Meadow mice are probably the worst mouse culprits in the garden this time of year. House mice might also do some damage, but they prefer to feed and live in our houses. Deer mice - the cutest of the lot, with their white bellies and oversize eyes and ears - feed mostly on seeds, berries, nuts and insects, so are off the hook for now.
You might point an accusing finger at moles. Don't. Moles are mostly carnivores. If you're going to fault them for anything, fault them for feasting on earthworms and for lending mice the occasional use of their tunnels. Mice runs are at the ground surface; moles tunnel below ground.
Mice can bear up to five litters per year of five babies each. When mouse populations soar, more heroic control measures are needed, including trapping, even poisons. The real-life creatures might look as endearing as Mickey Mouse, but don't be fooled. Besides damaging plants, mice also spread such ills as Lyme disease.