Cannas are not that easy to grow but with a little care you get some great flowers in the summer. Actually, they’re a little like old-fashioned dahlias in as much as they are tender, not liking frost at all.
Cannas are grown from rhizomes, which you can buy in the spring, when they should be placed in a pot of compost and kept warm; a conservatory or unheated windowsill is best.
Water sparingly until they start growing, then increase the watering regime. They like rich moisture retaining soil, and really do need hardening off in May so that by the end of the month they can go outside, where they’ll grow quickly. Keep moist and mulch to retain water, they like it damp.
In late September / October, lift them and place in a frost free environment in large containers – we used to use peat but now use peat alternatives. They need to be around 50C and then in spring, divide the rhizomes and start all over again.
Less popular than they used to be, I think they’re worth the effort!