Dig corms out of the ground in fall if you live in an area where the ground freezes in winter. Lift them out of the ground before ground-freezing weather begins. If you live in a warmer climate you don't have to lift your corms, yet they'll be susceptible to disease and crowding, which could affect the quality of the next year's blooms.
Loosen the ground around the base of the glads with a spade. Pull the corms out by hand.
Shake any excess soil off each corm. Cut the plant off the corm with a pruning shear. Cut as close to the corm as possible.
Rinse the corms under running water. Spread them out on a shallow tray in a well-ventilated area. Leave the corms to "cure" for three weeks. As the corms cure, a cork layer will form between the original corm you planted and the new corm that formed in the ground.
Break off and discard the old corms. Dust the corms lightly with a combination fungicide/insecticide dust.
Store the corms through the winter in a mesh bag, open paper bag or cloth sack. Do not cover the corms with anything. The ideal storage environment is a room with good air circulation, with temperatures between 38 and 58 degrees Fahrenheit.
Select a planting area with well-drained soil in full sunlight. Use soil test kits to test for soil pH and nutrients. Glads grow best in soil with a pH of 6.7 to 7.0. Most garden soil that supports a good crop of vegetables or weeds will support glads. If a soil test indicates a lack of nutrients, use a balanced, 5-10-10 commercial fertilizer. The numbers indicate the fertilizer's percentages of nitrogen, phosphorus and potassium.
Dig a hole about four times as deep as a corm's diameter. Place the corm in the hole, pointed side up. Cover with soil. Allow 6 to 8 inches of space between corms.
Position stakes where you plant corms, if necessary, as some glads will blow over in windy conditions.
Treat glads with insecticide to control thrips during the growing season. Glads are susceptible to thrips, which are tiny tan or black insects.