Culture
Best grown in moist, organically rich, well-drained soils in full sun. Plant rhizomes 4-6” deep and 18-24” apart in spring after threat of frost has passed. Remove entire flowering stems immediately after bloom. Rhizomes are reliably hardy in USDA Zones 7-10, but can be lifted in fall for overwintering in colder climates. In fall, cut plants to the ground after first frost and lift rhizome clumps for winter storage in a dry medium (peat or vermiculite) in a cool dry location than does not fall below 40°F. Rhizomes may be occasionally sprayed with water in winter to make sure they do not become so dry that root shriveling would occur. Container grown plants can be stored in their containers in winter. Propagate by division in spring before replanting outdoors.
Noteworthy Characteristics
Canna is a genus of around 10 species of rhizomatous, tropical and subtropical, herbaceous perennials that produce flower spikes from summer into early fall atop erect stems sheathed in large paddle-shaped leaves. Cultivars are available with colorful foliage and flowers in a range of warm colors including red, orange, yellow, pink, and creamy white. The flowers are attractive to hummingbirds.
Genus name comes from the Greek word kanna meaning "reed".
‘Australia’ is a popular purple-leaved cultivar that grows 4-5’ tall. It features burgundy-black leaves (to 10-20” long) that hold the foliage color well through summer. Bright red flowers (to 3” across) appear in racemes atop burgundy-black stems from mid-summer to fall. Dramatic foliage provides considerable ornamental interest when the plants are not in flower.
Problems
Rhizomes may rot in poorly drained wet soils. Leaf spots, rust and bacterial blight may occur. Watch for aster yellows. Japanese beetles, caterpillars, leaf rollers, slugs and snails may chew on the foliage.
Uses
Group or mass in beds or borders. Effective planted with both annuals and perennials. Foundations. Large containers. Leaves are particularly impressive when backlit by sun.