Bringing the Outdoors In
Answers to the most-asked questions about overwintering potted plants.
By Teri Dunn, Gloucester, Massachusetts
Although you've enjoyed your collection of houseplants, potted tropical plants and tender herbs out on the deck or patio all summer long, the show can't last. The days are growing shorter, temperatures are dropping and, if you don't do something soon, a cold snap could turn them into a sorry ensemble of limp, blackened leaves and stems.
But before you decide to cart your entire collection indoors for the winter, take a careful look at each candidate. Sentimental favorites and valuable plants take priority. As for the rest, maybe some can go into the compost pile or you can take cuttings from others. For the chosen few, however, it's important to make certain they are in good health and have no hitchhiking pests.
Here are answers to several common questions about overwintering your most-prized garden possessions:
Q: How should I prepare potted plants?
A: A little grooming is in order. Remove spent or damaged flowers, stems and leaves. If you discover the plant is pot-bound—the plant has grown too large for its container, resulting in tangled and matted roots—go ahead and repot. Otherwise, wash pot exteriors with a bit of soap and water (don't forget the saucers).
Q: Is it possible to keep potted herbs producing over the winter?
A: You can try! Imagine how wonderful a winter soup or stew would be with a bit of fresh thyme or rosemary!
For best results, put a potted herb in a bright, warm spot (4 to 6 hours of light a day is the minimum for most) indoors. A kitchen windowsill is often ideal, not just because the plant will be close at hand when you're cooking, but seeing it daily will remind you to take good care of it. Water as needed (don't overwater), and turn the pot occasionally so growth remains even on all sides.
Q: I'm worried that my tropical plants will suffer from lack of sunlight when I transfer them inside. Can I supplement with artificial light?
A: Yes! If your home doesn't have a bright spot for them, which can be a challenge this time of year, supplement or replace with artificial light. Fluorescent bulbs are much better for the job than ordinary incandescent bulbs—because the combination of warm and cool light in fluorescent bulbs provides the whole light spectrum.
Aficionados have been known to devote entire rooms, or areas of them, to potted plants grown under fluorescent lights. There are even tables and carts available from specialty suppliers for this purpose—maybe worth the investment if you have a sizable collection.
Q: How should I care for my houseplants during the winter months?
A: It's good for houseplants to rest during the winter months. This doesn't mean you should neglect them, but feeding or watering them at summertime rates isn’t a good idea, either.
If your plants are not actively growing, fertilizing them is wasteful and only causes salt buildup in their potting mix, which can damage the plants. Gauge when to water by occasionally poking a finger an inch or so into the mix—if it's dry, water.
In truth, what your overwintered houseplants may appreciate most of all is a humidity boost, because heated rooms get dry. Try placing pots on trays filled with pebbles, so drained water evaporates around them. And group your plants, since there's strength in numbers. An occasional misting may also benefit them.
Q: How should I place tender potted plants by a window?
A: If your winters are freezing, icy or snowy, do not let individual leaves touch the window glass—the cold likely will damage or kill them. Move the pots back a few safe inches, making sure that the sunlight still reaches them. Alternatively, you can leave the pots on the sunny windowsill or shelf by day and move them "inland" to a table or counter each night.
Remember that south-facing windows get the best sun this time of year. East-facing ones may also be a good choice.