Bulbs: summer flowering
Summer-flowering bulbs begin to bloom when spring-flowering bulbs begin to fade. Summer-flowering bulbs produce plants that generally don't tolerate frosts well, but provide color and a long-lasting bloom display. These plants prefer partial to full shade.
For best selection and optimum results, purchase bulbs, corms, tubers, rhizomes and roots early in the spring. They're available through catalogues, garden centers and nurseries. Purchase only bulbs that are large, firm and free of defects. Some of the most popular summer-blooming bulbs include caladium, calla lily, canna, dahlia, gladiolus and tuberous begonia.
Caladiums are often chosen for their foliage, which can be white, pink, red or green. These plants do best in shady areas or containers and prefer a highly organic, moist growing medium. After killing frost, dig up these tubers and store them in a cool, dry place until next spring.
Cannas provide a lush, almost tropical look to flower borders, and are available in many colors and heights. For best results, plant these rhizomes six inches deep and approximately 18 inches apart. After killing frost, dig up the rhizomes and store them in dry peat moss in a cool, dry, ventilated place until the following spring.
Dahlias are a long-lasting flower with showy blooms that range in color and size to fit most cutting gardens. Plant dahlias two to three inches deep only after the last spring frost. In autumn, allow the roots to remain in the ground for two weeks after a killing frost so they can thoroughly ripen before you dig them up. Dig carefully so that the roots do not break apart. Dry the roots, then pack them in perlite or vermiculite and store in a cool, dry place until spring.
Gladiolus, which can be used for cut flowers, are available in many colors and perform well in Colorado. For best results, plant these corms three to six inches deep after the danger of frost has passed. Do not allow them to go to seed, because it will adversely affect corm development. When the tops die back, dig and sort the corms for storage.
Tuberous begonias may be single or double flowering, and are available in white, pink, yellow, red and bicolor. To achieve optimum results, plant these tubers one to two inches deep in a shady location that is high in organic matter. Keep the site relatively moist, but not overly wet. After the first frost, dig up the tubers and store them in sawdust in a cool place until spring.
Calla lilies are best known as a cut flower. They are easy to grow in partial shade or as a container plant. Handle these rhizomes much as you would tuberous begonias.
For more information, see the following Colorado State Extension fact sheet(s).
For "Commonly used plant terms" refer to message number 2008.
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Updated Friday, April 19, 2013