Canna 'America'

A spreading, herbaceous perennial that grows up to 1.5m tall.

Intense scarlet flowers with long petals contrast with the lush, dark purple-green leaves.

Prefers a sheltered site in full sun to partial shade with free-draining soil. Will tolerate drier soils.

Always choose healthy, well-grown plants and plant after autumn rains. Before planting, ensure the root ball is saturated and remove the planter pot with minimal root disturbance. Trim any broken roots and plant at the same level as in the container. Dig a hole twice the diameter of the root ball, press in and water once planted. Make sure plants are watered well until established if planting in a drier period. Plant with some general slow-release fertiliser and then every spring apply organic fertiliser (such as blood and bone) at a handful per square metre. Plant approximately 60cm apart.

If planting rhizomes in containers, fill a large pot 6 inches from the top with well-draining potting mix. Add perlite to help with drainage. If your pot is very large, you can plant two or three canna rhizomes in each pot. Backfill your pot or hole with additional soil until the rhizome and roots are well covered. Gently press the mix around the base and water in well.

Apply mulch annually to improve soil health and moisture retention and suppress weeds. Mulch also protects the rhizomes from the winter temperatures in colder areas. In a home garden, it is important that spent stems are removed at ground level as soon as the flowers finish. Stems that start to die back make the clump increasingly unattractive, so give them regular grooming to keep them looking good. The entire clump should be cut back to ground level in June or July when flowers finish. Lift and divide the entire plant every 3 to 5 years, as this helps maintain vigour.

Like all members of the ginger family, cannas are greedy growers. Give them plenty of fertiliser every spring and summer to ensure the clump remains vigorous.

In climates where the ground freezes in the winter, you can dig up your plants in autumn after the first frost, let them air dry for a few days and store the rhizomes in a cool dry place in a paper bag. You may get lucky and manage to preserve them for next spring planting.

Cannas in Auckland can suffer from rust in summer when there is high humidity. The affected stems should be cut back and burnt if possible. Rust spores are wind-borne, so if the material is left on the ground or composted it can re-infect the plants. They are also susceptible to fungal leaf spot. This is also best removed and burnt. Caterpillars and earwigs can be troublesome, as they often chew flowers and foliage in summer.

Perennial Garden

Cannas are a good source of nutrients: the rhizome contains about 25% starch in a highly digestible form. The starch grains are very large and easy to separate from the fibre in the rhizome. Cannas are still considered an important food crop in the Andes of South America and parts of Asia. The main agricultural form (Canna discolor) has been bred to be a very large, fast-growing plant with rather insignificant yellowish flowers on 3m high stems. The thick rhizome is grated to a pulp, washed and strained to remove the fibre. The starch can then be dried and used as flour or as a substitute for arrowroot. In Vietnam, it is grown extensively to make cellophane noodles. The smoke from burning leaves is insecticidal. In Peru, the young rhizome is traditionally baked for 12 hours to make a sweet stew, which contains about 10% protein.

Canna seeds are pea-sized are exceptionally hard. They have been used as shotgun pellets in India (hence the common name "Indian Shot"). The seeds are used as beads in jewellery and have been used in baby rattles and musical instruments. A purple dye can be extracted from the seed; fibers from the stem of the plant are also used to make jute and paper. Canna have been used for phytoremediation (the use of plants to absorb toxins from soils) to remove toxic heavy metals from pig waste and to remove excess fertilizer and insecticides from greenhouse runoff.