As temperatures dip in autumn and the threat of frost hovers, most plants take the opportunity to rest from the hard work they’ve put into creating blossoms and fruit. “All plants need a breather after seed is produced and before active growth,” says Michelle Reid, the horticulture foreperson for Toronto Parks, Recreation & Forestry. “In northern climates like ours, this dormant period coincides with winter.” But while hardy shrubs and perennials can withstand the cold under their blanket of snow, our shivering fragile specimens need extra protection to survive.
That’s where overwintering comes in. “Overwintering offers the gardener a number of benefits,” adds Reid. “First and foremost, it saves money. It’s easy, takes little space and the gardener can quickly increase his or her quantity of unusual and expensive species. And having plants indoors improves our well-being, as they cleanse the air during the long winter.”
Suitable for most plants, especially tropicals and tender perennials (plants that we treat as annuals, but are perennials in warmer zones), one of the tricks to overwintering is to find the right place for the right plant. Some like a sunny spot by the window, while others prefer a cool, dark resting place.
Tender perennials, such as impatiens, coleus and geraniums, can be trimmed back and placed by a cool, bright window. If you want to keep them over the winter, dig and pot them up in containers before bringing them indoors. Some ardent gardeners nurture cuttings and plant them outdoors after the frost date passes, but others find it too much bother, so they buy new plants each spring.
Before the first frost in the fall, dig up summer-flowering bulbs, corms, tubers and rhizomes. Trim back the foliage, brush off the soil and lay them out in a dry, airy, warm place for two weeks. Divide if necessary and over- winter them in dark, cool, dry yet airy surroundings—the basement is perfect. The storage container depends on the type of bulb, corm or tuber. Gladioli and any bulbs with a papery husk should be placed in mesh bags with plenty of air circulation. Don’t water, but do check them once a month and discard any that show signs of rot. Dahlias, cannas, caladiums and tuberous begonias can be stored uncovered in either trays or boxes loosely packed with vermiculite or dry peat moss. Check every month to see that they aren’t drying out—you may need to sprinkle a few drops of water over the vermiculite or peat moss to keep it plump. (Don’t overdo the water or rot may set in).