Gladiolus flowers are a popular sight in the summer garden. These plants naturally multiply through self-propagation, allowing a single planted structure to yield multiple new plants over time. This multiplication is a built-in feature of the plant’s biology, offering gardeners a simple way to expand their colorful display each season.
The Role of Corms and Cormels
The underground structure of a gladiolus is not a true bulb but a corm, a swollen, solid stem base that serves as a food storage unit. The corm ensures the plant’s survival during its dormant period. Each growing season, the corm planted in the spring is used up and dies, but a new, larger corm forms directly on top of the old one, ready for the next year’s growth cycle.
While stacking new corms renews the plant, the primary method of multiplication involves smaller offsets called cormels. These tiny structures develop in clusters around the base of the main corm. Cormels are genetically identical clones of the parent plant, making them the most reliable way to propagate a specific variety. A single large corm can produce anywhere from 30 to 100 cormels in a year.
Harvesting and Separating the Multiplied Stock
The best time to harvest and separate the corms and cormels is in the autumn, typically six weeks after flowering or when the foliage begins to turn yellow. For non-hardy varieties, the corms must be lifted before the first hard frost to prevent freezing. After digging the entire plant clump, cut the stalk down to about one to two inches above the corm.
Curing involves drying the harvested corms and cormels in a warm, airy, and well-ventilated location for two to three weeks. This drying process prevents storage rot and makes separation easier. Once cured, the shriveled, old “mother” corm at the base can be easily removed and discarded, leaving the new, plump corm ready for storage. The cormels should be gently detached from the base of the new corm and stored separately for future planting.
Caring for Immature Cormels
Cormels separated and stored over winter can be planted the following spring to grow new flowering stock. They are planted shallower than mature corms, usually about two inches deep, and spaced for proper development. Because these are immature structures, they will not produce flowers in their first growing season, focusing instead on developing foliage and root systems.
The small cormels produce only grass-like foliage, requiring full sun and consistent watering to grow sufficiently large. Gardeners should ensure the cormels receive adequate nutrition throughout this growth phase. It typically takes between one to three years of annual lifting, storing, and replanting for a cormel to reach the size needed to produce a full-sized flowering spike. Focusing on the larger cormels during selection will yield flowering plants sooner.