Gladiolus, often called the “sword lily” due to its striking, upright foliage, is a popular choice for cut flower arrangements and garden displays. The plant grows from a corm, a solid, bulb-like structure that stores energy for growth. Understanding the full season of the gladiolus involves knowing when its dramatic flower spikes will appear and how to manage the planting and overwintering cycle.
Establishing the Planting Window
The gladiolus season begins when the corm is placed in the ground, a process highly dependent on local climate conditions. Planting must occur after the danger of the last hard frost has passed in the spring, as the corms cannot tolerate freezing temperatures. Gardeners should wait until the soil temperature consistently reaches at least 55 degrees Fahrenheit before planting.
In most temperate regions, this window opens in late spring, often from April through June. Corms should be planted pointed side upward, buried four to six inches deep in well-drained, amended soil. Planting too early in cold, wet soil can cause the corms to rot.
Defining the Bloom Season
The actual flowering period is directly tied to the timing of the initial planting. Impressive flower spikes typically emerge approximately 60 to 90 days after the corm is placed in the ground, depending on the variety and weather conditions. This growth timeline means the peak bloom season falls in the summer months, starting around mid-July and extending into early autumn.
Each single flower spike provides a display for a relatively short time, with florets opening sequentially from the bottom to the top over one to two weeks. Intense heat and full sun exposure can accelerate the growth cycle, causing blooms to appear slightly earlier.
Maximizing the Display Period
Since a single corm provides only a short period of bloom, gardeners use succession planting to extend the overall display. This method involves staggering the corm planting over several weeks rather than placing them all in the ground at once. Starting after the last frost, a new batch of corms can be planted every two weeks.
This staggered approach ensures that as the first group of gladioli begins to fade, the next group is starting to produce flower spikes. The final planting should occur about 10 to 12 weeks before the first expected hard fall frost, allowing time to mature and bloom before cold weather arrives.
End-of-Season Care and Storage
For gardeners in colder climates (USDA Hardiness Zones 7 and below), the annual cycle concludes with digging up the corms to protect them from winter freezing. Corms must be lifted once the foliage has yellowed or after the first light frost has killed the leaves, but before a hard freeze occurs. The plant stems should be cut back to about one or two inches above the corm when they are dug up.
Curing and Winter Storage
The next step is the curing process, where the corms are allowed to dry in a warm, dark, and well-ventilated area for two to three weeks. Curing removes excess moisture from the corms and their husks, which prevents rot during storage. Once completely dry, the old, shriveled mother corm at the base should be gently removed and discarded, separating it from the new, larger corm that formed above it.
The cleaned corms can then be dusted with a fungicide powder to protect against disease and stored for the winter. Ideal storage requires a cool, dry location with temperatures maintained between 35 and 45 degrees Fahrenheit. Storing the corms in mesh bags or old nylon stockings ensures adequate air circulation, which keeps them viable for replanting the following spring.