Gladiolus bulbs must be dug up and properly stored each winter if you want them to continue to bloom for you in years to come. But it's important to the plant's health that the glad bulb, or corm, is allowed to undergo a cold period in very early winter. For this reason, they should remain in the ground until the earliest frost completely kills the stalks and leaves back. Simply allow the foliage to die on its own before digging up gladiolus bulbs, or corms.
Dig several inches away from the gladiolus plant's base with a fork. Work it all the way around the corm to loosen it, and pry it gently upward without cutting any more roots than necessary. Bulbs can easily be damaged by improper handling, and bruising will promote rot while in storage.
Gently brush as much soil as you can from the corm and roots. Inspect them closely, and discard any that are soft, or show signs of rot or disease. Don't remove the papery husks from the corms.
Use a clean sharp knife to cut the foliage off about one inch above the new corm that has formed at the base of the plant's stem. It rests on top of the old mother corm, which is now shriveled up.
Spread the corms out in a single layer in a dry area with good ventilation at room temperature, around 65 to 75 F and out of direct sunlight. Let them "cure" for three weeks.
Break off the small cormels that have grown on the underside of the shriveled up mother corm, which can now be discarded. Cormels will bloom for you in two to three years. Dust all the remaining corms and cormels lightly with powdered fungicide.
Label brown paper bags clearly with permanent ink. Pack gladiolus corms and cormels loosely in them, and store the between 35 to 45 degrees. Choose a dark, dry, well-ventilated area until you're ready to plant them again next spring.
Check on the corms every two to three weeks while they are in storage. Discard any that soften or begin to rot.