How Tall Do Cannas Grow?

Growing Cannas

• Plant or grow cannas in full sun for at least four hours per day in loose, fertile soil. Plant rhizomes in early spring when danger of hard frost is past, and the plants produce stalks and large flowers the first year. Space rhizomes 12 to 18 inches apart and cover them with 2 inches of soil. Cannas require moist soil, so don't let beds dry out. Water them deeply once a week. Mulching well after planting helps maintain moist soil and protects underground rhizomes. Deadheading, removing spend flowers, isn't essential because flowers keep coming either way. Newer hybrid types can get messy without occasional tidying. Dividing plants every few years encourages continued strong blooming. According to Horn Canna Farm, both rose and tomato fertilizers work well for cannas.

Canna Cold Hardiness

• In U.S. Department of Agriculture Plant Hardiness Zones 7 to 10, leave cannas in the ground all winter. For cannas grown in zone 5 and colder, dig up and store the rhizomes for the winter. Zone 6 is something of a "maybe" climate for cannas because in some years it may be safe to leave them in the ground but in other years they freeze. For cannas you particularly cherish, in Zone 6 the motto should be, "When in doubt, take them out."

Cannas in Containers

• Plant cannas in containers in colder climates six to eight weeks before the usual outdoor planting date for your area. Start the plants in a greenhouse or sunny window to get a head start on the growing season. In the spring after danger of frost is past, remove your started cannas from their containers and plant them outside. Some gardeners in USDA zone 5 and colder grow cannas in containers making it easier to bring them in to protect them from freezing temperatures. Divide the plants and repot them more frequently if you grow them in containers. Container growing is ideal anywhere for creating a tropical feel on a small patio or deck. Be particularly vigilant about watering potted cannas.

Canna Varieties

• Most canna hybrids (Canna x generalis) are 4 to 6 feet tall and include varieties like Bengal Tiger with pale-yellow and green-striped, banana-type leaves and brilliant orange-deep orange flowers, and Cleopatra, with torch-like red and yellow blooms and burgundy-striped leaves. Dwarf cannas include apricot pink Tropical Sunrise, brilliant red President and Lenape, gold with red dots. Giant cannas reaching 8 or 9 feet tall include Black Night with velvety bright red flowers and bronze foliage, and salmon pink The City of Portland.