Glorius Gladioli
By Bob Chapman
“Glads” are gorgeous, with dramatic, upright spikes three to five feet tall, and each covered with dozens of closely crowded florets of single or multi-colors. They are towering tumults of color with florets so perfect it seems a cloud of butterflies has alighted en masse. The effect is magnificent whether in the garden or in the vase.
The Plant
Gladiolus grows from corms, a swollen underground stem base composed of solid tissue unlike bulbs, which have scales. These perennials feature sword-shaped leaves (in fact, the name is derived from gladius, the Latin word for “sword”) and are unbranched. The flowers start opening at the bottom of the stalk, continually opening new florets with the passage of time.
Purchasing and planting suggestions
You can purchase corms from January until June. The best-producing corms are those that are high crowned for their width and about 1 ½-2 inches wide. Older, flatter corms are less vigorous.
Plant corms at a depth at least three times the width of the corm or 3-4 inches deep. Although they will grow in most soils they will do better if the soil is enriched with organic matter and fertilizer is added at the time of planting. A teaspoonful of a general-purpose fertilizer placed in the bottom of the hole is sufficient. Many gardeners drive stakes at planting next to the corm to support the taller stalks.
For successive crops of flowers in the garden, or for use as cut flowers, plant a few every other week. They will bloom anywhere from 65 days to 100 days after planting, depending on the area where you live and the climate. In warm winter areas you can plant gladioli from January to May. In colder areas start planting when the soil warms up.
Fertilizing and watering glads
Gladioli do not need additional fertilizing after planting when growing them in native soils. Feed them with a water-soluble fertilizer, such as Miracle-Gro or Jobes, when growing gladiolus in containers.
Keep the soil moist to prevent drying out the corm and thus risk losing the entire plant. Moisture availability is important when flower spikes are beginning to form. A lack of water may produce shorter flower spikes, smaller florets, and smaller corms for the next season.
Digging and storing the corms
Lift the corms when the foliage yellows, but is not completely dead. After lifting, cut the tops just above the corm. Discard the small cormlets unless you are interested in planting and growing on until they reach flowering size (about three years). Discard any corms showing signs of disease. Let the corms dry for 2-3 weeks in a spot out of direct sunshine. When the old corm at the base separates easily the new corms are ready for storage for the winter. Store the corms in a mesh bag, nylon stocking pantyhose or a paper bag with holes punched in for air circulation. NEVER store your corms in a plastic bag.
Dormancy requirements
In mild winter areas your gladioli require 6 weeks dormancy at 40 degrees F. or 2 months at 50 degrees F. average temperature before planting next spring. Keeping them in an unheated garage usually suffices.
Pests of gladioli
The major pest of gladiolus is thrips. This tiny insect is blackish and about 1/25 inch long. It is very active in attacking both flowers and leaves. The thrips will rasp the foliage, leaving whitish streaks. Florets, when attacked by thrips, are often discolored, misshapen and often unable to open. Control thrips by spraying with Isotox or a product containing pyrethrins.
Diseases attacking glads
Leaf spots caused by one of several fungi usually do not harm the plant but are unsightly. Treating with a spray of daconil will control any outbreaks.
Various rots present in the soil will cause scabs and the destruction of the corm. If this happens, next season plant your corms in a different location. These rots are usually persistent in the soil and there is no chemical treatment that will rid the soil of them.
Cutting the flowers
Gladioli are raised by many to provide cut flowers. To get the maximum amount of time of the cut flowers, pick when the first florets are beginning to open. Cut the flower spikes early in the morning or evening for maximum freshness. Remove the flower spikes with a slanted cut from a sharp knife, leaving at least four leaves for corm development.
Care of cut flowers
Immediately place the spikes in a deep container of warm water to keep from wilting. Leave them in a cool, dark place for several hours before arranging. This will help flowers harden off and last longer. As the florets fade, remove them to keep the glads looking their best. Change the water daily and at this time give the stems a fresh cut to extend the life of the blooms.