Gladiolus, often referred to as the Sword Lily due to its distinctive foliage, is a favorite among gardeners for its dramatic, towering flower spikes. While the individual flower spike is a one-time event, the plant grows from a corm, a perennial storage organ. This means the gladiolus can survive and produce new blooms in subsequent seasons, provided it receives proper care after its summer display concludes.
The Gladiolus Bloom Cycle
The floral display of the gladiolus is borne on a single, vertical stalk that emerges directly from the corm. This structure is a spike composed of many individual flowers, or florets, arranged along its length. These florets open sequentially, starting with the lowest bloom and working upward. This staggered opening ensures the color lasts for an impressive period, often extending the bloom time of a single stalk up to two weeks. Once the uppermost floret has opened and faded, that specific flower spike is finished and will not rebloom later in the season.
Post-Bloom Maintenance
As soon as the last florets on the stalk begin to wither, the gardener should perform a practice known as deadheading. This involves cutting the spent flower stalk just above the highest remaining leaf, ensuring the foliage remains intact.
Leaving the foliage untouched is essential for ensuring future blooms. The leaves utilize photosynthesis to convert sunlight into carbohydrates. This energy is then translocated downward to the corm to initiate the formation of the daughter corm, which will produce the next year’s flower.
The leaves must be allowed to yellow and die back naturally, typically taking six to eight weeks after the bloom fades. Prematurely cutting the green foliage starves the corm, resulting in a smaller corm that may not produce a flower spike the following season. The leaves signal they are finished when they turn yellow or brown.
Preparing Corms for Next Season
For successful reblooming in areas where winter temperatures fall below freezing, the corms must be “lifted” or dug up before the first hard frost. This process begins after the foliage has fully matured and browned, indicating the corm has stored sufficient energy. The plants are carefully dug up, and the remaining stem is trimmed back to within an inch or two of the corm structure.
The freshly dug corms must first undergo a process called curing. This involves drying the corms in a warm, well-ventilated, and dark location, ideally at a temperature range of 70 to 80 degrees Fahrenheit, for two to three weeks. Curing allows the outer husk to dry completely, forming a protective, papery layer that helps prevent rot during the dormant period.
Cleaning and Division
After curing, the gladiolus corm requires cleaning and division. The shriveled, spent structure at the bottom is the original “mother corm,” which must be peeled off and discarded. This leaves the plump, new “daughter corm” for next season’s planting.
Small, bead-like offsets, known as cormels, are often attached to the base of the daughter corm. These can be separated for propagation, though they will typically take two to three years to reach blooming size.
Overwintering Storage
The cleaned and dried corms are then ready for overwintering, which requires specific environmental conditions to maintain dormancy. They should be stored in a cool, dry, and dark environment with good air circulation, such as an unheated basement or root cellar. Temperatures must remain consistently between 35 and 50 degrees Fahrenheit. Storing them in breathable containers, like mesh bags or paper sacks, prevents moisture build-up and ensures they remain viable until they can be replanted the following spring.