Did you recently drag some of your favorite plants indoors to “save them” from Mother Nature’s cold snap? Not exactly sure what to do with them now? Many plants grown as perennials in warm climates are not hardy enough to withstand the freezing temperatures in Northern areas. Northern gardeners can leave these plants outdoors to die at the end of the season or they can overwinter them until the next growing season. Many gardeners have great success with overwintering annuals such as geraniums, tropical mandevillas, hibiscus and a whole host of other great patio plants.
Overwintering involves protecting the plant from the cold, either in the garden or in a sheltered place. There are many overwintering techniques, ranging from covering dormant plants with a thick layer of mulch to moving plants to coldframe, sunny windowsill, or cool basement. What works for one type of plant might be fatal to another.
An easy way to overwinter some plants is to grow them in containers year-round and use them as houseplants or on the sun porch during winter. Slow-growing woody plants such as lavender, rosemary, and tarragon make the transition from outdoor plant to houseplant and back very successfully and can thrive for many years.
You can hold many types of nonhardy plants, often called tender perennials, indoors over winter. Cutting back, digging up, and potting plants growing in the garden is one option for overwintering, but this may cause transplant shock, especially if the plants are large. An easier way to save tender perennials is to take and root cuttings, and then keep the cuttings indoors over winter. Many summer bedding plants, including impatiens, begonias, geraniums, and coleus can be overwintered this way. Rooted cuttings take up less space indoors than entire plants, and there is less chance of inadvertently overwintering diseases and insect pests. Take cuttings from your overwintering plants in late winter to propagate more transplants to move outdoors once the weather warms. To keep them from getting leggy as winter progresses, pinch them or keep them under plant lights.
Fleshy roots of cannas, dahlias, and even four o’clocks (Mirabilis jalapa), along with tender bulbs like caladiums (Caladium spp.) and tuberous begonias (Begonia spp.) can be dug and stored over winter.