Gladiolus, often called the sword lily due to its tall, spiky foliage, is a striking summer flower grown from an underground structure known as a corm. Proper post-bloom care is necessary to ensure the plant stores sufficient energy, allowing it to produce vibrant blooms again the following year. The goal of cutting and subsequent care is to redirect the plant’s resources away from flower and seed production and toward the subterranean corm.
Removing the Spent Flower Spike
The first step after the display fades involves the immediate removal of the spent flower spike, a practice known as deadheading. This must be completed promptly once the last floret has withered to prevent the plant from developing seed pods. Use clean, sharp bypass pruners to make a precise cut on the main flower stalk, just above the highest remaining set of green leaves. Leaving at least four pairs of healthy leaves intact is important for the plant’s immediate survival and energy production. This initial removal is distinct from the final cut of the foliage, which happens much later in the season.
The Importance of Leaving Foliage Intact
After the flower spike is removed, the remaining green foliage begins its most important work of the season. These sword-like leaves become the primary site for photosynthesis, converting sunlight into sugars that are stored within the corm below the soil line. The corm requires approximately four to six weeks of active, green foliage after blooming to store enough energy. Cutting the foliage prematurely interrupts this crucial nutrient transfer, resulting in a small, weak corm that may not bloom the following season. The green leaves should remain untouched until they naturally begin to yellow and die back, typically in the early fall, indicating the corm has completed its nutrient uptake and is entering its dormant phase.
Preparing Corms for Winter Storage
Gladiolus corms are not cold-hardy and must be lifted and stored indoors in climates below USDA Zone 7. Preparation begins when the foliage is fully yellowed or after the first light frost. Trim the dead foliage down to a stub, leaving only one to two inches of stem attached to the corm. Gently lift the corm clump from the soil using a garden fork, digging wide of the stem to avoid damage.
Shake off the excess soil and move the corms to a warm, dry, and well-ventilated area for a curing period of two to three weeks. Curing allows the outer husk to dry and harden, creating a protective layer that resists decay during storage.
After curing, clean the corms by separating the new, plump corm from the shriveled mother corm, which can be discarded. Brush off any remaining soil and inspect each corm, discarding any that appear soft, mushy, or diseased. Store the cleaned corms in a cool, dry location between 35 and 50 degrees Fahrenheit. Mesh bags, old nylon stockings, or cardboard boxes allow for necessary air circulation, preventing moisture buildup and rot.