By Larry Hodgson
Question: I have a young brugmansia that will be spending its first winter with me. It’s planted in the northeast part of my garden where it ought to be covered with about 3 feet (90 cm) of snow. Should I protect it for the winter and if so, how?
Answer: Sorry to disappoint you, but your brugmansia, also called angel’s trumpet (Brugmansia spp.), with its stunning large, trumpet-shaped flowers, is by no means hardy enough for your climate. You live in USDA hardiness zone 3 (AgCan hardiness zone 4) where winters plunge well below freezing and stay there for weeks, yet the brugmansia is a subtropical plant: even the cold-hardiest cultivars can barely tolerate 23 °F (-5 °C), and even then, only for short periods of time. Even under 3 feet (90 cm) of snow, your plant will have no chance of surviving the winter no matter what protection you offer it.
Gardeners much further south, in hardiness zone 8, sometimes manage to keep a brugmansia alive in a sheltered place by mulching it deeply. It will then die to the ground … but sprout again when warmer weather returns in the spring. Only in hardiness zones 9 to 12—the tropics, essentially—can you expect a brugmansia to grow outdoors on without special winter care.
Indoors or Bust!
If you want to keep your brugmansia alive without having to move to Florida or Costa Rica, you’ll need to bring it indoors for the winter. If so, you have two options.
Treat It Like A Houseplant
If you have a large, brightly lit window, you can keep your brugmansia growing all winter by continuing to water it as needed. Provide good humidity, too, otherwise the plant may lose many of its leaves. It may be necessary to rinse its foliage with water from time to time to prevent spider mites, very common on indoor plants in the winter when the air is dry.
Otherwise, prune your brugmansia severely, cutting its branches back by at least half, thus cutting off all its leaves. Then store it in a cool but frost-free spot (below 50 °F/10 °C, if possible), possibly a basement or garage. It can be in the dark, too, as the plant will be essentially dormant. During winter, water very little, just enough to prevent the soil from drying out completely.
In March, it will be time to wake your brugmansia up. Move it to a well-lit room and start watering and fertilizing it again. It will be in bloom again by summer.