|
|
By Linda Naeve, Reiman Gardens, Iowa State University Extension
Editor’s Note: This article first appeared as Reiman's Pick for the week of Oct. 11, 2004. It is reprinted here with the author’s permission.
For most plants, well-drained soil is a necessity. Wet, soggy soil reduces the oxygen supply to the roots, resulting in stunted growth, pale foliage and stem and root rot. Cannas are an exception to this rule and are as healthy with their roots under water as they are growing in garden soil.
Cannas are native to tropical Central and South America and thrive in warm weather. They are perennials in USDA Hardiness Zones 7 to 10. However, in cold, northern climates, they are considered tender perennials. This means they will grow year after year if dug in the fall and stored indoors throughout the winter months. The large, plump rhizomes are the storage organs that keep the canna plant alive until planted the following summer.
Modern canna cultivars, classified as Canna X generalis, are hybrids between two Canna species. Canna cultivars offer a wide range of plant heights from 18-inch dwarfs to nearly eight-foot tall giants. The bold, colorful flowers rise above the foliage and bloom in various combinations of red, pink, yellow, salmon or orange.
Large, broad canna leaves add textural variation and a tropical look to border gardens, containers and water gardens. Depending on the cultivar, the foliage may be green, burgundy, or yellow and green stripes.
Cannas grow best in full sun and bloom from mid-summer through frost. Plant the rhizomes in the garden after the threat of frost is past and keep the soil moderately moist. Remove the spent flowers to encourage season-long blooms.
For water gardens, plant a six- to eight-inch tall canna in a two-gallon container filled with garden soil; cover the soil with a layer of pea gravel. Set the pot on the margin of the pond or on a crate so that the rim of the pot is just below the water surface.
After the foliage dies back in the fall, cut canna stems to about four inches above the soil. Carefully lift the plants out of the soil using a garden fork. Crumble the loose soil from the rhizome; do not wash or cut them apart. Allow the roots to dry in a shady, warm area for several days then store in paper bags in a cool, dark area. Check them occasionally and discard any rhizomes that show signs of rotting or shriveling.
Divide the rhizomes in the spring leaving one or two "eyes", or growing points, on each division. Allow the cut surfaces of the rhizome to dry for a few days before planting.
Cannas grown in annual beds at Iowa State University's Reiman Gardens will soon be dug and stored for next year's displays, leaving space for hundreds of tulip bulbs.
Cannas add a tropical look to border gardens, containers, and water gardens. Depending on the variety, they grow 18 inches to eight feet tall and bloom in red, pink, salmon, orange and yellow. The rhizomes on these tender perennials can be dug after the foliage dies back and stored in paper bags in a cool basement.