Gladiolus, often simply called “glads,” are striking summer-flowering corms that bring dramatic vertical appeal to any garden space. They are popular for their tall, showy spikes of blooms, making them a favorite for both garden displays and cut flower arrangements. Planting these flowers correctly requires understanding how to group them for the best visual impact and ensuring that the density supports robust plant health.
Optimal Group Size and Spacing
Gladiolus corms are best planted in clusters rather than in a single, straight line. A recommended grouping size is a minimum of five to seven corms, though some gardeners prefer nine or ten. Planting in odd numbers, such as five or seven, generally creates a more aesthetically pleasing appearance.
Within these clusters, proper spacing is necessary. Each corm should be situated approximately four to six inches apart. Plant the corms at a depth of four to six inches, pointed end upward, to provide stability for the tall, heavy flower spikes.
When the primary goal is harvesting cut flowers, planting in straight, manageable rows may be more practical. Maintain the same four to six-inch spacing between individual corms.
Extending the Display Through Staggered Planting
Since a single gladiolus corm produces one flower spike that blooms for only about two weeks, planting all corms at once results in a short-lived display. To enjoy continuous vibrant flowers from mid-summer until fall, employ succession planting, which involves staggering planting times.
The ideal schedule is to plant a new cluster of corms every ten to fourteen days. Begin this process shortly after the last expected frost date in spring, once the soil temperature has warmed to at least 55°F. Continue planting new groups every two weeks until early summer, since gladiolus generally take 60 to 90 days to reach the blooming stage.
Essential Bed Preparation for Healthy Growth
Location and Support
Successful gladiolus cultivation starts with choosing the right location. The towering flower spikes require full sun, meaning at least six to eight hours of direct sunlight each day, which promotes stronger stems and abundant flowering. Without adequate light, the plants may become leggy and produce fewer blooms. Because large-flowered varieties can reach heights of five feet or more, select a location that allows for staking or providing supports near the planting groups to prevent the heavy spikes from bending over.
Soil and Nutrients
The corm’s health depends heavily on the soil’s composition, requiring well-draining, loamy soil. Heavy clay soil must be amended significantly with organic matter, such as compost or well-rotted manure, to improve drainage and aeration. Before planting, incorporating a balanced fertilizer, like a 5-10-5 analysis, provides the necessary nutrients for vigorous growth.