Bushy dwarf plants have 3-4 in/8-10 cm white colored blooms. Cannas are not hardy, but they produce tubers, like dahlias and tuberous begonias. Dig up rooted tuber just before frost and trim excess foliage from root. Store in a bushel of sand in a cool, dark area (frost free) until April. Re-pot tubers in gallon containers for July blooms.