Its difficult to decide which part of the Tropicanna canna lily (Canna "Phasion") is more beautiful: the broad, variegated dark green, orange and pinkish leaves or the spring- and summer-blooming stalks of sunset orange, hummingbird- and butterfly-attracting blooms. With moderate care and maintenance, Tropicanna canna promises a show-stopping tropical display.
Location, Location, Location
The Tropicanna canna lily grows as a perennial in U.S. Department of Agriculture plant hardiness zones 7 to 11, where it thrives in bright, full sun. The plant prefers a rich, well-draining, organic soil. Canna lilies grow from fleshy roots known as rhizomes. If you're planting Tropicanna lilies from rhizomes, mix 1/3 cup of a 10-10-10 fertilizer per rhizome into the soil to boost growth. Only plant rhizomes in spring after the threat of frost has passed.
As individual flowers die throughout the summer, remove the flower-bearing stems under the spent flowers. This will encourage the plant to produce another flowering shoot and more flowers. Canna lilies are water hogs that thrive in moist, even wet or soggy conditions. Monrovia recommends watering whenever the top 3 inches of the soil are dry. Check the leaves occasionally for caterpillars, which may roll the leaves to create shelters. Handpick and drown caterpillars in soapy water. If the canna has dead or damaged leaves, remove them when you see them. Although the plant doesn't usually have disease problems, leaving old foliage may encourage fungal problems.
Tropicanna canna thrives in rich soil. Starting in early spring, fertilize once a month until the end of the growing season. For a 5-10-10 granular fertilizer, apply 2 pounds per 100 square feet. If you're using a 10-10-10 fertilizer, use 1 pound for each 100 square feet. The first number refers to the amount of nitrogen in the fertilizer. Supplying excessive nitrogen can cause an abundance of foliage at the expense of flowers. Follow the label instructions carefully, watering well before and after fertilizing so you don't burn the plant's roots.
In USDA zone 7 and below, Tropicanna will die unless you dig up and store the rhizomes. After the first killing frost, when the above-ground portion of the plant has died, dig up the rhizome. Dig about 1 foot away from the stem, to keep from accidentally cutting into the rhizome. Rinse the rhizome off with water and clip off the top. Store the rhizomes in a plastic bag in an area where the temperature is between 45 and 60 degrees Fahrenheit. Rhizomes can be replanted in the garden after the last spring frost. Space the rhizomes 1 to 4 feet apart, at a depth of 4 to 5 inches.