Overwintering dahlias, cannas and begonias

You can never quite predict how severe our winter weather will be, but you don't need a crystal ball to know that some plants will need protection or lifting to survive a winter. Dahlias come into this category.

These are frost hardy tuberous Mexican plants which in some parts of the country, coastal areas of Cornwall for instance, gardeners might get away with leaving the tubers in the ground. However most of us have to dig up the tubers because cold winters kill them. Wait for the first frost to blacken them and then lift them. Plastic trays used for some vegetables make ideal resting places, the black plastic rigid mesh boxes that are often stacked up in supermarkets are ideal. You will get fewer losses if you cover them with dry compost and keep them somewhere cool and frost-free.

Begin to water again in March and then pot them up. If the plants are very large break them into pieces because over-large dahlias don’t produce much flower.

There are other tender plants which should be lifted in October, including cannas and begonias. Canna rhizomes should be lifted in the autumn and stored in a frost-free environment in barely-moist compost or leaf mould.

Tuberous begonias grown in the ground should be lifted before the first hard frosts and left to die back before being stored in a well ventilated, dry place over the winter. Container-grown plants should be brought under cover during the winter and 'potted on' into a slightly larger container each year in spring.