Tropicanna canna lilies (Canna x generalis Tropicanna) are extravagantly colored plants for full sun. They have bright orange flowers and variegated red leaves that catch your eye even when the plant is not in flower. Tropicanna has a long flowering period, blooming for more than four months in the trial gardens at the University of Georgia. This canna variety grows 4 to 5 feet tall and 2 feet wide. Cannas are hardy only in U.S. Department of Agriculture plant hardiness zones 8 through 10. They are grown as tender perennials elsewhere in the United States and the fleshy roots (rhizomes) must be lifted and stored inside during the winter.
Planting and Growing Care
Choose a site for Tropicanna in full sun in moist, well-drained soil. Amend the soil with organic material to improve drainage, if necessary. Wait until after the last expected frost to plant cannas outdoors.
Add fertilizer to the planting soil at the rate called for in the product directions and mix well into the soil. Use a balanced garden fertilizer, such as 10-10-10.
Dig a hole for each rhizome deep enough that the top of the rootstock is 4 to 5 inches below soil level. Cover with soil, firming it to remove any air pockets around the roots. Water well. Space plants 18 to 24 inches apart.
Water once a week during drought periods. They grow best in moist soil but can tolerate drought once established.
Fertilize again in mid-summer to encourage the formation of more flower buds.
Remove spent flowers to keep Tropicanna flowering.
Prune plants back to 4 to 6 inches above the soil after the leaves have been blackened by frost.
Dig the clumps and gently remove most of the soil with your fingers. Canna roots are brittle, so don't shake them to remove the soil.
Place the rhizomes in a sheltered spot for several hours, until the roots and remaining soil are thoroughly dry. This may take a few hours to several days, depending on the weather. If necessary, cover the roots at night to protect them from freezing temperatures.
Store rhizomes in wire crates, mesh bags or large boxes in a cool, dry location where temperatures stay above 40 degrees Fahrenheit. Inspect the roots occasionally and discard any that become shriveled, soft or moldy.
Propagation and Restarting Growth
Divide large root clumps in spring, before planting. Slice down through the crown, making sure that each section has at least three to five buds.
For earlier outdoor bloom, start cannas inside six to eight weeks before the last expected frost date.
Plant the cannas at the same depth they will grow outdoors, 4 to 5 inches below soil level. Use a large enough container to fit the roots comfortably.
Place the containers in a sunny window or use grow lights once the rhizomes sprout.
Harden the cannas off for a week before planting outdoors by putting the containers outside during the day but taking them back inside at night.