Gladiolus, often called the “sword lily” due to its tall, upright foliage, is a popular choice for gardeners seeking dramatic, vibrant summer color. These stately plants produce impressive flower spikes valued both in the garden and as cut flowers. New growers often ask if a gladiolus plant can produce more than one flower spike in a single season. The answer is that an individual gladiolus corm is programmed to bloom only once per year.
The Single-Bloom Nature of Gladiolus Corms
Gladiolus grows from a corm, a swollen, underground stem structure that stores nutrients. This corm contains the energy and pre-formed tissues needed to produce a single flower spike during one growing season. Once the plant has bloomed, the original, or “mother,” corm becomes depleted of stored energy and shrivels.
The plant’s energy then shifts to developing a new, larger replacement corm directly on top of the old one, storing energy for the following year’s bloom. The plant also produces several small offsets called cormels around the base of the new corm. These cormels are baby corms that can be grown over several seasons to produce new flowering plants.
Strategy for Continuous Summer Color
Since a single corm blooms only once per year, gardeners use successive planting to create the illusion of continuous color. This method involves staggering the planting of corms over several weeks rather than planting the entire batch at once. Planting a small group of corms every ten to fourteen days ensures a continuous rotation of new flower spikes emerging in the garden.
The initial planting should occur after the danger of the last spring frost has passed and the soil has warmed. Bi-weekly plantings can continue until mid-summer, about ten to twelve weeks before the first expected frost date. Gladiolus takes between 70 and 100 days from planting to flowering, depending on the variety. Selecting a mixture of early, mid, and late-season varieties can further extend the flowering window.
Post-Bloom Care for Future Seasons
Once the flowers on the main spike fade, deadheading should be performed to redirect the plant’s energy. This involves removing the spent flower stalk, which prevents the plant from wasting resources on producing seeds. The green foliage must be left completely intact after deadheading.
The leaves photosynthesize sunlight and transfer that energy down to the newly forming replacement corm underground. This process is necessary to “recharge” the corm, making it strong enough to produce a flower the following year.
In colder climates (USDA Zones 7 and below), the corms are not reliably winter-hardy. They must be lifted from the ground after the foliage has naturally yellowed and died back in the fall. After curing and storing them in a cool, dry place over winter, these corms will be ready to plant again the following spring.