Cannas grow from a starchy underground tuber. This heat-loving plant is hardy in USDA plant hardiness zones 8 to 11. Cannas grow in loose, well-draining loamy soil and full sun. The flowers bloom in late summer to early fall in an array of bright-colored blooms. Seedpods form after the flowers are spent in mid to late October. Cannas grow from seed or from root division. The foliage dies back in the fall. New growth emerges from the underground tubers the following spring.
Soak canna seeds for 24 hours in cool water prior to planting. If the seeds have not swelled slightly after soaking, rub them gently between two pieces of sandpaper to rough up the seed coating.
Start canna seeds in early spring for planting the following spring. Fill a seed-planting tray with a well-draining seed-starting soil mixture. Make 1- to 2-inch-deep holes 2 inches apart using a pencil or your index finger.
Place one canna seed in each hole and cover with soil. Pat down the soil firmly with the palm of your hand and water until the soil is damp all the way through.
Put the tray in a greenhouse or warm room where the temperature is around 68 to 75 degrees F. The seeds will germinate in three to nine weeks.
Transplant the seedlings to 6-inch pots when they are 2 inches tall. Fill the pots with a well-draining potting soil mix and place one seedling in each pot so that the base of the stem is 1 inch lower than the lip of the pot. Fill the pot to the top with the soil mix.
Keep the seedlings between 68 and 75 degrees F for the first year, then move them outside in the spring or early summer after the last frost has passed. Select a site that has deep, well-draining loamy soil and wind protection.
Make one planting hole for each canna. Dig the hole slightly larger and as deep as the root ball. Slide the canna from its pot and place it into the hole. Fill in the soil and pat it down firmly. Water the soil until it is damp to a depth of at least 5 inches.
From Root Segments
Fill an 8-inch planting pot halfway with a well-draining potting soil. Place one section of the canna tuber into the pot and cover it with 2 inches of soil. If there is growth on the tuber, plant that part facing up; otherwise, lay the root tuber flat onto the soil. Start cannas in early spring for summer planting.
Water the soil until it it is damp all the way through. Place the pot in a heated greenhouse or covered porch where the temperature is between 68 and 75 degrees F.
Transplant the canna starts outside in early summer. Dig holes that are slightly larger than the planting pot the starts are in. Slide each start out of its pot and place it into a planting hole. Cover each root ball with soil and pat it down firmly. Water until the soil is damp to a depth of 5 inches.