It’s time to plant glads

Richard Bogren, Gill, Daniel J.

For Release On Or After 02/19/10

By Dan Gill
LSU AgCenter Horticulturist

The tall flower spikes of gladiolus add elegance to the flower garden. Derived from species native to South Africa, the modern hybrid gladiolus grows from a corm and has been a favorite of Southern gardeners for generations.

We often call them glads; but an old name for gladiolus is sword lily, which refers to its sword-shaped leaves. (Like the term gladiator, gladiolus is derived from the Latin word for sword.) They are easy to grow and produce beautiful flowers in nearly every color of the rainbow. And the corms are relatively inexpensive to buy.

Select and plant gladiolus corms now through March. Don’t worry about cold weather; the foliage of glads will withstand late frosts. Glads grow and bloom best at moderate temperatures, and those planted during this period will bloom in April and May.

I’ve found from experience that planting corms after March often leads to disappointment. Although corms planted later will grow and bloom, the intense heat of mid summer weakens the plants, and the quality of the flowers is not as good. In addition, high populations of the insect thrips that have built up by then are devastating to the flowers, and spider mites attack the foliage. By being planted early, glads escape summer heat and pest problems during their flowering period.

Purchasing larger, high-quality corms will produce the best results. Look for jumbo-size gladiolus corms for the best flowers. Large number 1 and number 2 size corms will also put on a good show. The older varieties and species glads often have naturally smaller corms than modern hybrids.

Gladioli look best when they are planted among other flowers or shrubs in clumps or groups of five, 10 or more. With their strongly vertical growth habit, they act like exclamation points in the garden and create contrast and interest in the middle or back of mixed borders and flowerbeds. If you want to plant them in a row, plant the corms in a zigzag, double row for a fuller effect. A single row generally produces a weak, wimpy appearance, particularly if the flower spikes start to lean.

With so many colors to choose from, don’t make the mistake of planting one of each color in your garden. A better effect can be achieved by choosing two or three harmonious or attractively contrasting colors and planting them together in small clumps of single colors.

A well-drained soil and a sunny location are essential for growing glads. Prepare the area for planting by digging in a 2- to 3-inch layer of organic matter and adding a light sprinkling of a general-purpose fertilizer. Thoroughly incorporate those materials into the area, and you’re ready to plant.

Plant jumbo corms about 5 inches deep; medium-sized corms 4 inches deep; and small corms 3 inches deep. Leave about 4 to 5 inches between corms. Cover the corms with soil, mulch them to prevent weeds, and water generously. The deeper planting of the jumbo corms will help reduce the need to stake them later on.

To provide extra support for the tall varieties, mound soil around the plant bases as they grow. When the flower stalks gain height, staking may still be necessary to prevent the plants from leaning over. For a more natural look, use green-colored bamboo stakes placed behind the stems out of view and tie them to the plants in two places using green twine.

Each gladiolus corm produces one large flower spike that blooms for about a week. To extend the flowering period, plant a batch of corms every two weeks from now until mid-March. This will ensure a succession of blooms during late spring and early summer.

Glads make outstanding cut flowers, and you may want to plant some extra corms in your cutting garden (if you have one), vegetable garden or other out-of-the-way bed for cutting. When cutting the flowers, leave at least four or five leaves on the plant to produce a new corm capable of blooming the next year.

Hybrid gladioli are hardy here and may be left in the ground over winter. However, you may find they deteriorate and cease blooming without annual lifting and replanting in fresh, prepared soil. In the late summer when the foliage turns brown, dig the corms, break off the brown leaves and the previous season’s withered corm and store the corms in a dry, frost-free location to plant next year. If you’re a lazy gardener like me, you may choose to leave the corms in the ground and see how well they return.

Some gladioli, particularly the older varieties, will return for years without digging and storing. The Byzantine gladiolus, also called corn lily, and the parrot gladiolus or Natal lily are excellent, long-lived species for Louisiana gardeners. Although not easy to find, the corms may be available from mail order companies that specialize in bulbs if you can’t find them locally.

Rick Bogren

1/4/2011 1:14:44 AM
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