As fall settles in, I check the temperature every morning, and today it was 8°C. It’s time to move plants and tubers indoors. Favourite summer annuals (like pelargoniums and tender herbs) anyone is hoping to keep going over winter should already have been brought indoors. They can survive these cool nights outdoors, but the adjustment to sudden warmth of house temperatures can shock them enough so that they drop foliage.
Last spring I purchased three Begonia boliviensis ‘Encanto Orange’ tubers from gardenimport. These made cascades of bright orange flowers all summer and are still in full bloom. (Other hybrids of this species are red B. boliviensis ‘Bonfire’ and double coral ‘Bellfire’.) They certainly were worth the cost, and I want to keep them for next year. After frost has lightly nipped them, I’ll remove the stems, lift the tubers and shake off the soil, and store them in the basement at about 10°C, buried in open plastic bags with vermiculite and peat moss (lightly misted with water). Other kinds of tuberous begonias can be saved over winter in the same way. If you’ve invested in expensive begonias like those in the Blackmore and Langdon strain, it makes sense to store them over winter to enjoy again next summer.
The timing of when to lift and methods for storing canna and dahlia tubers are different. Cannas are quite frost sensitive, so when they’ve had just a night or two of light frost damage to their foliage, dig up the tubers, brush off the soil clinging to them, and store in open plastic bags with vermiculite and peat moss (lightly misted with water) at about 10°C. Dahlias need to have a few hard frosts to significantly blacken their foliage before lifting. Then, dig up the tubers, clean them and store at the same temperature as cannas, in open plastic bags with vermiculite and peat moss.