Calhoun County, AL – Seasoned gardeners know that gladiolus corms can safely overwinter in the ground in USDA hardiness zones 7–10 without freezing. However, experienced gladiolus growers also understand an important long-term truth: corms need periodic rest.
Every four to five years—or sooner—gladiolus corms should be dug and rested. When left in the ground too long, corms gradually lose vigor. This results in thinner, weaker stalks that require more staking and produce smaller blooms. Proper care and rotation help restore strength and ensure healthy flowering seasons ahead.
When it’s time to dig corms, leave the full stalk attached during the drying process. Hang the stalks indoors in a shed or well-ventilated area for several weeks. Once completely dry, remove the stalk from the corm. Store corms indoors using breathable materials such as spandex pantyhose or burlap, allowing for proper airflow during winter dormancy.
Corms should be replanted after the last frost. Gladiolus thrive in well-drained soil and benefit from a soil mix that includes mulch to help reduce fungal issues. Heavy clay soil increases the risk of disease and should be avoided. Likewise, gladiolus should not be planted in areas designed for moisture-loving plants such as canna lilies.
Each corm needs adequate space to grow—plant them approximately four inches apart in a well-drained location. Bamboo stakes paired with jute string are effective, natural options for supporting tall stalks. Some gardeners stagger their plantings to enjoy continuous blooms into early summer.
Monthly applications of fish fertilizer support healthy growth throughout the season. Water once weekly at ground level, taking care not to wet the stalks, which can encourage disease.
By fall, each mature corm will produce small offshoots known as cormels. These should be gently removed from the adult corm before drying and storage. Leaving cormels attached causes them to draw energy away from the adult corm, reducing bloom quality the following season. Adult corms are stored indoors, while cormels should be left in the ground to mature. Cormels take two to five years to produce blooms, making it important to mark planting areas to avoid disturbing them during development.
With proper care, gladiolus reward gardeners generously. Cut blooms can last up to a week in a vase when water is changed daily—bringing the beauty of the garden indoors.
Betty Clark is a contributing writer. She has been an organic gardener since 1998. The signature flower she grows is Dahlias. She has a straw bale garden, a raised bed garden, and an in-ground garden. Both her surnames are from agricultural farming families (8 generations). Her hobbies include ancestry research, antiques, continued education classes, and workshops. She also has a background in marketing & promotions, including expos. To contact Betty Clark with gardening questions: bettyclark2151959@gmail.com
