Growing Gladiolus in the Tropics

    Gladiolus produce enjoyable blooms and are relatively easy to grow. The plants require well-drained soils in a sunny location. Bulbs, actually a corm, which are 1 1/2 to 2 inches in diameter, will produce full, attractive flower spikes. Small corms 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 and about 2 inches apart. A general rule of thumb is plant deeper in sandy soils and shallower in heavy soils. Supporting the flower stem may be required in windy areas and in rocky soils where it is difficult to dig a deep hole.

Unfortunately, gladiolus blooms can be plagued with thrips. These are tiny, slender black insects, often difficult to see with the naked eye. They will cause white streaking on the blooms as well as the leaves. Flowers can also become misshapen and discolored.

Note: These insects are the culprits which also cause silvery to brownish scarring on the surface of avocado and citrus fruit. This damage, however, does not harm the internal fruit quality and is strictly cosmetic.

To save the bulbs for next year’s planting, they can be dug up at the end of the season, cleaned off and stored in a dry, cool place. Pack bulbs in dry peat moss or wood shavings in a brown paper bag or cardboard box.   In high rainfall areas, bulbs that are kept in the ground are susceptible to rot. Sometimes it is just better to buy new bulbs each year.

Certain hardy, spring flowering bulbs like tulips and hyacinth generally require a chilling period in order to produce blooms. When these bulbs are grown in mild winter climates, a 6-8 week chilling period in the refrigerator is required.

Planting bulbs in large containers is also a good idea. Containers will provide good drainage and the bulbs are easily planted and dug up. And, if need be, containers can easily be moved out of the rain.  

Attention Big Island Residents: I will be teaching a class, Vegetables in the Home Garden, on Saturday, February 21, 9:30AM -12:30PM at UH-Hilo Campus. Call 974-7664 to register; there is a fee.