Q. Can I add mulch to my beds in the middle of winter?

A. Mulch serves a number of purposes in the garden, depending on when it's applied. In winter, where there's no snow cover, mulch helps insulate plants' roots. A few inches of mulch can provide a cushion of as much as 10 degrees above ambient air temperatures — just enough to keep roots growing. And certainly, a top dressing of mulch offers cosmetic appeal, making the yard look cared for at a time when the landscape can look a little underwhelming.

Ideally, mulch for the winter is added in the fall to protect against sudden and extreme temperature dips before plants have had a chance to fully harden. If you find yourself in the middle of winter and you didn't apply mulch in the fall, or if it needs to be replenished, it's not too late to add it, even if the ground is fully frozen. As winter wears on, subsequent thaws and refreezes can heave perennials out of the ground or, at the very least, put additional stress on them; mulching helps prevent that.

There's no need to add more than two to three inches. And be sure to pull the mulch away from the trunks and stems of plants to avoid "mulch volcanoes" and to avoid giving cover to rodents who want to feed on the inner bark of the plant.