When it comes to keeping your favorite tender perennials alive through the winter months, knowing your own space is as important as knowing a plant’s climate of origin.
I have a neighbor with a geranium problem. She’s powerless to resist saving any geranium she fears might be destined for the trash, rescuing plants from the grocery store or taking them off the hands of friends who can’t be bothered to bring potted geraniums indoors when the weather turns cold. In winter, her living room is transformed into a crowded geranium orphanage.
While you don’t have to sacrifice entire rooms of your house to enjoy those colorful blooms and sweet-scented leaves year after year, Saving Container Plants authors Alice and Brian McGowan recommend carefully considering your space when investing in perennials that can’t live year-round outdoors:
“Anyone can overwinter tender perennials, but your available facilities will limit and define the possibilities. The options you choose will then depend on how elaborate you want to get and also on your personal preferences.
“The key to successfully bringing a plant through the winter indoors is understanding its natural dormancy cycle. Some plants continue to grow during their indoor vacation and thus need a warm, sunny location. Others enter a stage of partial dormancy and are more suited to a spot that’s sunny but cool. Some plants go completely dormant and simply need to be properly stored for the winter.”
Here are their tips for nurturing geraniums through the winter months:
Hardy to at least 45° F (7° C)
OVERWINTERING. Cool and bright. Water sparingly; remember that the South African winter is a dry one. Keep dead leaves picked off, and trim spent flower clusters as needed.
COMMON PEST PROBLEMS. During the winter months, geraniums may be troubled by rust; discourage this problem by removing and disposing of infected leaves. Botrytis, which can also be a seasonal issue, will be similarly discouraged by the removal of spent blossoms and the prevalence of good air circulation.
A Sunny Windowsill
Some tender perennials — many of them tropical plants like begonias and alternantheras — will be perfectly happy on a sunny east-, west-, or south-facing windowsill. Treat these as you would a houseplant, watering and fertilizing on a regular schedule. If you keep the thermostat between 65 and 70° F (18–21° C), the temperature inside your house will remind these plants of winter in the tropics. This may cause their growth rate to slow slightly, but for the most part, the plants will continue to be in active growth. They will need every bit of sunlight you can supply. Lacking sufficient sun, you might keep them happy with a supplemental source of light, like the fluorescent lights that many gardeners use for vegetable seedlings.