Calla and canna lilies
Canna and calla lilies grow well in hot sites throughout Minnesota. Though the names are similar, the plants are not.
Calla lilies or callas (Zantedeschia species) are not true lilies. They are related to jack-in-the-pulpit and caladium. Unlike jack-in-the-pulpit, they are not hardy in Minnesota. The tuber-like rhizomes must be dug up and stored inside over the winter.
Callas have a broad, trumpet-shaped flower called a spathe that wraps around the yellow finger-like spadix. The spathe is actually a modified leaf and may be white, yellow, or pink/rose/purple. The spadix holds the tiny, true flowers. Its leaves are arrowhead-shaped and solid green or green with silver or white flecks.
Zantedeschia aethiopica, the white calla, is native to Africa where it is considered a weed. Its spathe can be up to 10 inches long, but is usually 4 to 6 inches long.
Callas may be grown as houseplants, in a sunny location, but for the best results, plant callas outside and enjoy them indoors as cut flowers. They should bloom mid to late summer for about a month.
Callas thrive in a deep, moist, rich soil in full sun. They will grow in part shade, but will not bloom as well. White callas will grow in boggy or alkaline soils.
Set rhizomes four to six inches deep and one to two feet apart. Fertilize each spring, after planting them, using 5-10-5 or 5-10-10. After frost has killed the foliage, dig up the rhizomes and store them in a peatmoss, vermiculite, or perlite. Leave the top of the bag open or punch holes in it for air exchange. The rhizomes should not dry and shrivel during storage.
Canna lilies or cannas (Canna x generalis) are native to tropical and subtropical areas. They are not hardy in Minnesota. Like callas, their rhizomes must be dug up in the fall after frost has blackened the foliage.
Cannas grow 1 1/2 to 5 feet or more, depending on variety. Their large, glossy green leaves are 6 to 12 inches wide. Their blossoms are clustered at the top of flower spikes which can be up to one foot long. Blossom size varies with the species planted. Cannas are available in red, rose/pink, yellow, red with yellow, and dark red with bronze foliage.
They make a very attractive planting for a large container, in raised beds or as background plants.
Cannas may be started indoors by planting them three to four inches deep in pots, then transplanting them outside. They will also bloom well if planted directly into the garden as soon as the soil has warmed and danger of frost has passed. Plant the rhizomes 3-4 inches deep and 1 1/2 to 3 feet apart. Cannas grow best in full sun and hot weather, providing they have adequate moisture and a soil high in organic matter. They will bloom in a warm site that gets part day sun, such as along a house wall. They bloom mid-summer to frost.
In the fall, dig up the rhizomes, cut the stems back to 2-3 inches, and let them dry. Leave them in a box in a cool part of the house where they will not freeze, such as a basement where the temperatures range between 40-50 degrees. Every few years, the rhizomes may be divided. When dividing, each piece must have an eye or growing point on it. Let the cut-up rhizomes dry for a few days before planting them.