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Tender Summer Blooming Bulbs, Corms, and Tubers
This article was published originally on 6/26/1998
Summer blooming bulbs are long-blooming and have showy flowers available in a wide range of colors. None of the following perennials will survive our cold Iowa winters. Therefore, they must be dug in the fall and stored indoors through the winter months. They should be carefully sorted and any damaged or diseased bulbs, corms, or tubers should be discarded prior to storage. All should be planted frost in spring after the threat of has passed and the soil temperatures are above 60 F. This usually means planting in mid to late May at the earliest.
Tuberous Begonias (Begonia x tuberhybrida) easily brighten a shady corner of the garden. They do best in protected sites in partial shade. They are available in upright and trailing types, single or double flowers, a wide variety of vibrant colors (bi-colors) and flower forms. Some of the flower forms available include camellia, cascade, carnation, and picotee types as well as the stamina-packed non-stop series. Height ranges from 8 inches to almost 2 feet with the majority staying within 8 - 12 inches. Plant the tubers 2-3 inches deep with the round side down. To get early blooming plants, home gardeners can plant them indoors 4 to 6 weeks before setting them outdoors in the spring. Keep these plants well watered and fertilize them regularly for continuous bloom. These beauties work well in containers and can be brought indoors in the fall for winter enjoyment. Those tuberous begonias left outdoors should be carefully dug after a killing frost. Dry tubers in a warm, dry location for approximately 2 weeks. Afterwards store in a box or sack with sphagnum moss or vermiculite in a frost-free area until replanting in spring.
Often mistaken for Allium, the loose globular blooms of Agapanthus (Agapanthus spp.) work well in many garden situations. They are particularly effective in containers as patio plantings. Plant corms 2 inches deep in full sun to part shade and a moist, well-drained soil. Flower colors are predominately lilac-blue to white. Container plantings make it easy to bring the plants indoors for the winter. Given plenty of sun indoors, they will continue to bloom throughout the winter.
The torch-like blooms and large, banana-like foliage of the Canna (Canna x generalis) make a bold statement in many summer gardens. Some varieties are giants reaching up to 6 feet tall. Use these garden giants as temporary screens or hedges. Dwarf forms reaching only 2-3 feet tall are also available. Flower colors on both the giant and dwarf forms include apricot, orange, red, white, pink, yellow, variegated, and speckled. Foliage color also ranges from bright green to variegated with combinations of yellow, maroon, red, bronze, cream, and green.
Cannas thrive in the summer heat and prefer full sun and a rich, moist or wet soil. They should be fertilized regularly for continuous blooms throughout the summer. Rhizomes are planted horizontally in the ground 4-6 inches deep. Dig the rhizomes after the foliage has been blackened by frost. Store the cannas in slightly moist sand or vermiculite in a well ventilated, cool, frost-free location until planting in spring.
Dahlias (Dahlia x hybrida) stand out like beacons in the summer garden. There are over ten thousand cultivated varieties of dahlias with every color represented except brown and true blue. With fifteen different flower forms ranging from pompons to cactus, it would be hard for someone not to like at least one variation. The blooms range in size from one to seventeen inches across! Dahlias range in height from two feet tall for bedding dahlias to twenty feet for giant tree dahlias. Blooming begins around the end of July and continues until frost.
Dahlias should be planted about six inches deep. Rows should be spaced about one and a half feet apart. The taller dahlias will require staking, as they cannot support themselves. As the plants develop, buds appear in the center of the dahlia. One of two things can be done at this time. The first option is to remove the center bud. This procedure is known as tipping to encourage lateral bud development. The other option, called disbudding, is to remove the lateral buds to encourage a large center bud. After a killing frost has destroyed the foliage, the tubers should be carefully dug, cleaned, labeled and stored in vermiculite for the long winter months ahead.
Although many of these summer blooming bulbs require more work to store over the winter, they are well worth the effort for their colorful and unusual blooms and foliage.
Year of Publication:
IC-479(17) -- June 26, 1998