Q. I have never quite understood when it is appropriate to apply winter mulch to my garden beds in autumn or winter. Can you clarify that for me? Also, how does one keep mice from burrowing through the mulch? – P.R., Holden

A. A winter layer of mulch is applied after the ground has frozen in fall or early winter. In most years, it is appropriate to apply the mulch sometime after Thanksgiving. The trick is to time the mulch application when the ground is frozen, but before a measurable snowfall has occurred.

Mulch is applied in an effort to prevent the ground from repeatedly freezing and thawing throughout winter and early spring. In this respect, mulch performs as insulation, keeping the ground frozen and thereby protecting overwintering plant tissues from the dangerous cycles of freezing and thawing that can cause decay, disease and premature emergence.

Mulch also is used to manipulate the microenvironment in which a plant lives. In some situations, some mulch materials can help increase the ability of marginally hardy plants to live through a Maine winter.

Fir boughs, dried leaves from deciduous trees, pine needles, straw and hay are among the materials used as winter mulch. All have their benefits and drawbacks. For some of the materials, the most obvious drawback is that the mulch material is either a prime habitat for mice, moles and voles seeking winter habitat or is a material easily traversed by the foraging critters. Some gardeners find it useful to scatter mothballs throughout their garden beds before applying mulch to discourage these marauders.

Q. How do I keep beautiful azaleas that were purchased locally at a retail outlet and obviously forced for spring and summer blooming, alive indoors throughout the winter months? I have one that is doing very well transplanted into a larger clay pot in a south window, but I foresee the day when it begins to dry up despite all the loving care I can give it. This has always happened in the past. Obviously it is too cold here to try to plant it outside and expect it to revive in a Surry spring. – R.Y., Surry

A. Without a botanical name for your particular azalea, it is difficult to give specific information about a plant, but I can offer this general advice: Azaleas require acidic soil, bright filtered light and moderate to high humidity. This is exactly the opposite of what most homes in Maine have to offer in winter, but it sounds like you’re on the right track setting your plant in a sunny south-facing window. Azaleas grown as houseplants should be fed regularly with a balanced liquid fertilizer (10-10-10 or 20-20-20) and should be misted daily with a spray bottle. If you are not opposed to synthetic fertilizers you might try a pH-influencing fertilizer that helps maintain an acidic pH level in the potting soil.

Keep the root mass of the plant moist but not saturated. Let the medium dry out between waterings, but do not allow it to become totally dry. Also, for a lush plant like azalea forced to grow in a pot, it is better to reduce the concentration of fertilizer (say to 25 percent of the recommended “full strength” rate) and feed the plant with every watering than it is to fertilize every fourth or fifth time it’s watered.

Q. I know it’s best to prune apple trees after the leaves fall off in autumn, but when specifically is it best to prune? Why isn’t pruning done in summer when the tree is actively growing? – R.S., Rockport

A. Apple trees should be pruned in winter, specifically in January or February. Pruning is undertaken in winter when the branching structure of the tree can be easily detected. Although it seems reasonable that a tree should be pruned when it is actively growing and able to repair wounds, summer is not the best time to prune for at least two reasons: First, it is difficult to make sound pruning decisions when the branching patterns of trees are masked by leaves. The purpose of pruning an apple tree is to direct plant growth in a way that maximizes fruit production and overall plant health. Each branch should be carefully considered before a cut is made, and that is a difficult task when a lot of leaves are in the way.

Second, apple trees are directing their energy to fruit production in summer. It is better to prune when the tree is in a dormant state. When growth resumes in spring, the tree begins to repair wounds.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, 512 North Ridge Road, Montville 04941, or e-mail them to dianagc@midcoast.com. Selected questions will be answered in future columns. Include name, address and telephone number.