The tall, vibrant flower spikes of the gladiolus, often called the sword lily, are a classic feature of the summer garden. A single gladiolus plant does not bloom all summer long, but understanding its growth cycle and using the correct planting approach allows gardeners to achieve a season-long display.
Understanding the Gladiolus Bloom Cycle
A single gladiolus corm, an underground storage stem, produces only one primary flower spike per season. It takes approximately 70 to 90 days from planting for the flower spike to emerge and begin opening its blossoms. The individual spike typically provides a bloom period of about seven to fourteen days as the florets open progressively from the bottom upward. The natural blooming window for most gladioli varieties falls between mid-summer and early fall.
The Technique for Extended Color
The secret to enjoying gladiolus blooms throughout the summer is succession planting. Instead of placing all corms into the ground at once, the total number is divided into smaller groups. The first group should be planted shortly after the last expected frost date in spring, when the soil has warmed sufficiently. Subsequent plantings are then staggered, most commonly every ten to fourteen days. This timing ensures that as the first batch finishes its bloom cycle, the next batch is just beginning to display its vibrant color.
This strategy should continue until about eight to ten weeks before the first anticipated fall frost, allowing time for the plants to mature and flower. A further refinement involves incorporating corms of different sizes. Larger corms generally bloom 10 to 15 days earlier than medium-sized corms, which helps extend the overall flowering period.
Supporting the Bloom: Essential Care
Gladiolus require consistent foundational care throughout their active growth. They thrive in full sun, meaning at least six to eight hours of direct sunlight daily. The soil must be well-draining, as the corms are highly susceptible to rot in overly saturated conditions.
During the active growth period, especially once the foliage and flower spikes appear, consistent moisture is necessary. Deep watering once a week, or more often during dry spells, helps maintain the steady moisture level. Taller varieties often become top-heavy as the florets open, making them susceptible to bending or snapping. Placing a slender stake next to the stem early in the season provides the necessary support. A balanced, low-nitrogen fertilizer can be applied when the spikes emerge to boost the quality and size of the final bloom.
What to Do When Flowering Stops
Once the flower spike has finished blooming, attention must shift to preparing the plant for the following season. The first step is to deadhead the spent flower stalk by cutting the stem off just above the foliage. This prevents the plant from expending energy on producing seeds, redirecting that energy back to the corm below the soil.
The green foliage must not be removed at this time. The leaves must remain intact for approximately six to eight weeks after flowering, or until they naturally turn yellow and die back. During this period, the foliage carries out photosynthesis, recharging the corm with the energy reserves needed for the next year’s flower spike.
In colder climates where the ground freezes, corms must be carefully lifted from the soil after the foliage has died back and before the first hard frost. These corms are then cured, cleaned, and stored in a cool, dry, and dark place over winter for replanting the following spring.