Q What is the best way to overwinter a canna plant?
Neil Ellis, Hampshire
A BOB SAYS You could leave it in situ, but that depends on your location. In Winchester, where you live, it’s not often cold for long, so with a free-draining soil, preferably light sand, I’d leave it in place. However, if very cold or wet weather is predicted, pile over dry, shredded bark, with a plastic flysheet tied on top to exclude excess water but let in air. Alternatively, once the canna has died down but before the frosts, dig it up with the rootball, dry it off, wrap in newspaper and store in a dry, frost-free place until spring. I would actually do both, leaving it outside for three years and then taking it inside…