The gladiolus, often called the sword lily, is a popular choice for adding vertical color to the summer garden. These impressive plants grow from an underground storage organ known as a corm, typically planted in the spring. The direct answer to whether you can plant a gladiolus in July is yes, but this timing pushes the absolute limit of the growing season. Planting at this mid-summer point requires specific adjustments to ensure the corm establishes quickly and has enough time to mature before the season ends.
Adapting Planting for Mid-Summer
Mid-summer planting requires modifying standard techniques to mitigate the stress of intense heat on the newly placed corm. The soil should be well-drained and loose, enriched with organic material like compost. This helps maintain consistent moisture without becoming waterlogged, which is important as heavy, hot soil can hinder root development and cause the corm to rot.
To encourage rapid root growth, pre-soaking the corms in lukewarm water for a few hours before planting is beneficial. Large corms should be planted approximately four to six inches deep, with the pointed end facing upward. This depth provides necessary stability for the tall stalks and helps keep the corm cooler and more consistently moist.
Immediate and consistent watering after planting is necessary for July corms. They require about one inch of water per week during their active growth phase, especially during dry spells. Applying a layer of organic mulch around the planting area helps conserve this moisture and keeps the soil temperature regulated, preventing the corms from overheating.
Understanding the Late Bloom Cycle
Planting gladiolus in July significantly compresses the growing period, directly impacting when flowers appear. Gladiolus corms generally require 70 to 100 days from planting to full bloom, depending on the cultivar and local weather. A planting date in early July will push the flowering time into late September or early October.
This late schedule means flowers will likely appear as the season transitions to cooler weather. The risk of an early frost becomes a significant factor, as frost can damage the tender flower spikes and foliage, abruptly ending the bloom cycle. Unlike spring planting, where corms are staggered for a continuous display, a single, concentrated planting in early July is the only practical approach to maximize available growing time.
The corm needs a full cycle of foliage growth after flowering to store energy for the next season. The shortened time between bloom and the first hard frost means less energy is stored compared to corms planted earlier. Selecting a variety with a shorter day-to-bloom requirement can improve the chance of a successful bloom and energy storage period.
Preparing Corms for Next Season
Since gladiolus corms are not hardy in colder climates (generally USDA Zone 7 and below), those planted in July must be lifted and stored for the winter. This process should begin four to six weeks after the flowers fade, or once the foliage naturally turns yellow, but before the first hard freeze. The foliage is cut back to about one or two inches above the corm before digging.
After lifting, the corms need a curing period to dry out and seal the surface, which prevents storage rot. They should be laid out in a warm, dry, and well-ventilated location, out of direct sunlight, for two to three weeks. Once cured and the outer husk is crisp, the original, withered mother corm can be detached and discarded from the base of the newly formed corm.
The new, healthy corms are then ready for winter storage in a location that maintains a consistent temperature between 35 and 45 degrees Fahrenheit. Proper storage involves placing them in mesh bags, nylon stockings, or open cardboard boxes to ensure good air circulation. This management ensures the late-planted corms remain viable and ready to produce a full bloom the following spring.