Gladioli are popular summer-flowering plants. They are valued for their long flower spikes which are excellent as cut flowers. The individual flowers bloom successively from the base to the top of the spike. Flower colors include white and shades of yellow, pink, red, and purple. Many flowers have brightly colored throats. The foliage is sword- shaped.
While often classified as bulbs, gladioli are actually corms. The structure is an enlarged stem with distinct nodes and internodes. The corm is enclosed in a paper-like covering or tunic. Gladioli are relatively easy to grow, but will not survive the cold Iowa winter outdoors. The corms must be dug in late summer or fall, dried and stored indoors during the winter months.
Glads should be planted after the danger of frost is past, about mid-May in central Iowa. Make successive plantings every 2 weeks for continuous bloom throughout the summer. The final planting should be made in early July. When purchasing glads, select corms 1 1/2 to 2 inches in diameter. They will produce large, attractive flower spikes. Smaller corms will produce foliage, but may not bloom. Planting depth varies with the size of the corms. Large corms should be planted 4 to 6 inches deep and 6 inches apart. Small corms should be planted at a depth of 3 inches. Gladioli require well-drained soils and perform best in a sunny location. Glads normally bloom about 8 to 10 weeks after planting.
Gladioli require little special care during the growing season. Control weeds by frequent shallow cultivation or by mulching. Water weekly during hot, dry weather. A 5-10-5 fertilizer may be applied as a sidedressing about a month after planting. Staking will be required in windy, exposed areas.
Glads for decorative indoor use should be cut as soon as the bottom flower on the spike has opened. Most of the remaining blooms will open when the spike is brought indoors and placed in water. When cutting glads, leave at least 3 or 4 leaves at the base of the plant. Early morning is the best time to cut flowers.
Remove all flower spikes on gladioli remaining in the garden as soon as the flowers have faded. Also continue to weed and water the area. When the leaves begin to turn yellow, the corms may be dug. Cut off the foliage about 1/2 inch above the corm. Then dry and store the glads indoors in a cool, well-ventilated location.
This article originally appeared in the May 14, 1999 issue, p. 59.
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