From our perspective, the gladiolus corm is a modified stem, a specialized storage organ that allows us to survive our dormant period underground. Each growing season, we deplete the energy stored within our original corm to fuel our spectacular floral display and leaf growth. As this happens, a new replacement corm forms on top of the old, shrinking one. Simultaneously, tiny secondary reproductive structures, which you call cormels, develop around the base of this new corm. These cormels are our primary method of vegetative propagation, ensuring our genetic lineage continues and spreads.
The ideal time to divide us is after our foliage has died back but before the ground freezes, typically in mid to late autumn. This timing is crucial. The yellowing and browning of our leaves signal that we have successfully translocated all our valuable energy reserves—starches and nutrients—from the dying foliage down into the new corm and the attached cormels. Disturbing us while our leaves are still green interrupts this vital process, severely weakening the stored cormels and jeopardizing their chances of successful growth in the following season.
Begin by carefully lifting the entire clump of soil containing our corms from the ground using a garden fork. Gently shake off the excess soil to reveal the structure. You will find the large, healthy new corm at the center, with the shriveled remains of the old corm beneath it and numerous small, round cormels clinging to the base. These cormels can range from the size of a pea to a dime. Gently break them away from the parent corm. It is beneficial to leave the papery husk (the tunic) on each cormel, as it protects the dormant bud inside from desiccation and disease.
Once separated, we require a period of curing and proper storage to mimic the dry conditions of our natural dormancy. Place the cormels in a single layer in a warm, dry, and well-ventilated area out of direct sunlight for approximately two to three weeks. This process allows any minor wounds to callus over and reduces moisture content, preventing rot during storage. After curing, store us in a cool, dark, and dry location, such as in a mesh bag or a box of dry peat moss or vermiculite, at temperatures between 35-45°F (2-7°C). This cold period is not strictly necessary but helps prepare us for spring planting.
Plant the cured cormels in the spring after the danger of frost has passed. Choose a sunny location with well-draining soil. Plant us about 1-2 inches deep and 2-3 inches apart. It is important to understand that cormels are juvenile structures. In our first growing season, we will not flower. Our sole purpose is to photosynthesize and gather energy, which we channel into enlarging and maturing our corm. By the end of that first summer, if conditions are favorable, we will have developed a full-sized, flowering-size corm that can be dug up, stored, and replanted the next spring to produce our characteristic flower spike.
