The Planting Zones for Cannas

About Cannas

• Hybrid cannas, sometimes called Indian shot or arrrowroot (Canna indica), grow from rhizomes, which are underground extensions of the plant’s main stem. Rhizomes hold reserves of nutrients and set out new growth to establish new plants. Cannas are tender perennials and are injured below 25 degrees Fahrenheit, so planting time varies from one U.S. Department of Agriculture plant hardiness zone to another.

USDA Zones 4 Through 6

• Cannas grow as annuals in areas where temperatures stay below freezing for long periods during winter, such as USDA zones 4 through 6. Rhizomes planted in April or May after the last average frost bloom from July on, but cannot survive the winter. In USDA zones 4 and 5, cannas planted indoors in pots can go directly to the garden after the last frost and bloom earlier in the summer, using the short season more efficiently than waiting until April or May to plant the rhizomes outdoors. After the foliage dies down, cut off the rhizome and approximately 6 inches of stem, dry them and store them in dry peat or other media at 40 to 50 F until the following spring.

USDA Zones 7 Through 8

• Cannas are considered tender perennials in USDA zones 7 through 8 and, covered by a thick mulch in a protected position, might survive mild winters. In USDA zone 8, last average frosts might occur as early as March, but in USDA zone 7, planting must wait until April. In both zones, rhizomes may be planted every week until May, provided plants sit 12 to 18 inches apart. Container-grown cannas require mulch if they are left outdoors or sheltered in a basement, garage or other unheated space during winter.

USDA Zones 9 Through 10

• Completely at home in USDA zones 9 through 10, cannas and need little protection except, perhaps, a sturdy stake for windy areas. Although cannas tolerate most soils, for a permanent home, they prefer a well-drained soil, rich in organic matter and consistent moisture -- some canna cultivars are even wetland plants. In USDA zones 9 and 10, planting becomes more a matter of timing than dodging frosty nights. For summer bloom, beginning in late June, plant rhizomes in February or March. When planting canna weekly for continuous blooms, stop planting in April when the soil is still cool enough to encourage root development -- by May, the fast-growing plants begin setting buds. You can leave the cannas in the ground all year in these areas.