Planting gladiolus in March is conditionally possible, depending entirely on your specific local environment. These summer-blooming flowers grow from a solid, underground storage stem known as a corm. For many gardeners, March is too early, but in warmer climates, an early planting can kickstart the season. The primary risk of planting too early is exposure to a late frost, which can fatally damage the tender new shoots. Understanding the precise conditions required allows gardeners to use the early spring window to ensure a longer, more abundant display of blooms later in the year.
Determining the Ideal Planting Window
The most important factor determining whether a March planting is viable is the temperature of the soil itself. Gladiolus corms thrive when the ground has warmed to a consistent temperature, ideally at or above 55°F (13°C). Planting into cold, waterlogged soil significantly increases the risk of the corms rotting before they can even begin to sprout.
The traditional guideline suggests planting about two weeks after the average last expected frost date for your region, which may push the date past March in many northern zones. You can accurately assess the soil temperature by using a simple thermometer plunged several inches into the ground. This measurement is a more reliable indicator than the air temperature alone.
Gardeners often utilize staggered planting to enjoy continuous color throughout the summer. This method involves planting a new batch of corms every two weeks from the moment the soil is ready until early summer. Initiating the first planting in March, provided temperature conditions are met, can significantly lengthen the overall blooming season. Since it typically takes 70 to 90 days from planting for the flowers to appear, an early start rewards you with blooms in late spring or early summer.
Preparing the Corms and Planting Site
Before planting, thoroughly assess the corms. Select corms that are firm, plump, and free from discolored, damaged, or soft spots. Healthy corms possess a smooth, intact husk covering and show no signs of mold or decay.
The planting site must receive full sun exposure for at least six hours daily to promote strong, upright flower spikes. Proper drainage is equally important because gladiolus will not tolerate standing water, which causes the corms to rot. To prepare the site, use a garden fork to loosen the soil to a depth of 12 to 15 inches.
Incorporating organic matter, such as compost or aged manure, into the loosened soil improves drainage in heavy clay and nutrient retention in sandy areas. This amendment creates an ideal environment where roots establish quickly. Soaking the corms in water for up to 24 hours just before planting can also help jumpstart germination.
How to Plant Gladiolus Corms
When planting, set the corm into the prepared soil with the pointed or bud-side facing upward. The recommended planting depth for standard-sized corms is between 4 and 6 inches. Planting at this depth helps anchor the tall flower stalks, reducing the need for staking.
Spacing between individual corms should be approximately 6 inches to ensure adequate air circulation and nutrient availability. If planting in rows for cut flowers, dig a single trench rather than individual holes for efficiency. For a visually denser display, group corms together in clusters of seven or more.
After covering the corms with soil, water the area thoroughly to settle the soil and eliminate air pockets. Following this initial saturation, reduce watering significantly until the first green shoots emerge. This practice prevents the corms from sitting in overly saturated soil, which could lead to disease.