Q. After weeks of low light and dry air, I struggle every winter to keep my houseplants happy, including philodendrons, snake plants, coleus, and large palms that are finicky and expensive to replace. So what can I do to bring them back to health?
A. The best medicine is repotting: Use rich potting soil, put them in the best light you can, and keep soils moist. For example, philodendrons thrive indoors, such as in sunny kitchens, in oversized pots to support trailing runners. To encourage healthy growth, cut them back proportionately several times a year. In contrast, coleus does not do well indoors unless it’s given a greenhouse atmosphere. Once brought in, it grows thin and leggy, then needs cutting back. A better plan is to cultivate new growth from the mother plant. Remove it from the pot, shake off the soil, and you’ll see a root structure that has begun to form tiny, new plants. Gently separate these and replant in new pots. Over time, coleus will fill out and will do well in filtered light, such as in a well-lit bathroom.
Large palms thrive by regularly removing dead stalks by hand from the base and separating them at the base, since two palms are often crowding each other in a restricted pot. When given ample room to grow, palms do well in a sunny spot and tolerate dimmed light. Water sparingly.
Q. Last year, my rose garden drove me nuts with black spot, yellowing leaves, and bug holes. I’m not ready to give up on them, but what can I do for healthier roses?
A. Black spot, rust, and Japanese beetles are a regular occurrence, especially on humid days. Almost all roses succumb at some point, but don’t be discouraged. Instead, prune roses and remove all infested growth. Then, to avoid spreading disease, place this material in trash bags and seal—don’t drop it on the ground. Plant fragrant marigolds at the base of roses and place a 4-inch layer of cedar mulch around each rose, since both serve as a bug deterrent. Spraying and dusting roses is not recommended, but a diluted Ivory liquid solution often does the trick, when sprayed on canes and leaves, as it temporarily glues Japanese beetles together.
Some of the hardiest roses are the old-fashioned variety. If unaltered by modern hybrid scientists, these species, or antique roses, are the healthiest and need little care, since they’re descended from wild species that grow in the hedgerows of Europe.
Q. During bleak winter months, I try to force branches into early blooming indoors. What are some species of trees and shrubs that are suited for this?
A. Tulip magnolia, forsythia, camellia, and quince are some of the best candidates for forcing indoors. Their bud-setting stage happened early and is now in place. If they grow in your garden, cut long branches and split the ends, then place everything in tall vases filled with warm water. It will take three to six weeks for buds to break open in a warm environment. Once in bloom, they may do so for another two to three weeks. It’s a welcome bit of early spring indoors, and the scents are lovely. Interestingly, the forsythia almost always roots while sitting in water-filled vases and can be planted outside, when all chance of frost has passed.
Victoria M. Elder, a professional creator of residential gardens, answers frequently asked questions from Baltimore-area gardeners. You can e-mail her with your gardening questions at firstname.lastname@example.org.