Gladiolus is a dramatic tropical flower that will catch the eye of everyone who visits your garden. Most of us are familiar with the blooms in cut flower arrangements, but the spiky form, sword shaped foliage and ruffled blooms make this plant a knock out in the garden too. Gladiolus will stand out like an exclamation point in mixed borders.
Glads grow from corms, which look similar to a spring flowering bulb. The plant is neatly packed into the corm and just needs soil, warm weather and moisture to emerge. When you purchase gladioli corms go for the ones that are plump with high centers. Avoid those that are large, thin and flat.
Select a spot in your garden that receives a full day of sun with loose, well-drained soil. If like me you have clay soil, plant glads in raised beds and containers or work in plenty of organic matter into the soil to a dept of 10 – 12 inches. Apply a well balanced, organic fertilizer when preparing the bed, and side dress them again at midway through the growing season.
Plant the corms about a month before the last frost date in your area; the foliage can take a light frost. Position the corms with the pointed side up about 3 – 6 inches deep depending on the size of the corm; the larger the corm the deeper it should be. Small corms should only be 1 -2 inches deep.
Glads need 1 inch of water per week. If rainfall is insufficient, soak the garden thoroughly when you water. Signs of water deficiency are short spikes, small flowers and production of small corms.
It usually takes 70 – 90 days after planting before the flowers emerge. Select early, mid and late blooming varieties for continuous color. If you only have one type, stagger the planting every two weeks for a longer bloom time. The top heavy flower spikes may need staking, especially if wind is an issue.
Shortly after foliage emerges the corm you planted will wither. As it fades it will produce a new corm and sometimes more than one. In zone 7 and colder these corms need to be dug and stored. Do this after a killing frost and before the ground freezes in winter. After digging shake off excess soil and cut the stem off just above the corm. Leave their husks intact. Cure them in a warm, dry, airy place for about 3 weeks then break the corms apart discarding the old, spent ones. Corms with two buds can be cut in half. You may notice small “cormels” alongside the corms. You can also remove and store these for planting the next spring. It takes a few years for them to bloom, but it’s worth the effort. Treat the corms and cormels for insects by dipping them in very hot but not boiling water, for two minutes and allow them to dry. Place prepared corms in a paper sack. Store in a well-ventilated place that’s dark, dry and 35 to 45 degrees F. Make sure they don’t freeze.
In areas where the ground does not freeze to the depth where your corms are planted, you can leave them in the ground covered with a layer of mulch.
Thrips can be a problem for gladioli. Leaves will appear streaky or flowers may be deformed, discolored or even fail to open. If you suspect thrips spray plants with an insecticidal soap following package directions.
Gladioli are exceptional for arrangements indoors. Cut the flower stalks that only have 1 or 2 blooms open so the rest can open in the vase. Leave the foliage intact to energize the developing corms. I like to place the flowers in warm water overnight so they can recover their vitality before arranging them. To extend the life of the bouquet remove faded flowers and cut 1 inch off the bottom of the stem every few days so it can continue to absorb water.
Good to Know:
Corms from lighter flower colors generally multiply more quickly than the darker colors and if mixed together the lighter colors will eventually outnumber the darker colors and that sometimes gives the impression that the glad’s are changing colors.