Gladioli, sometimes called ‘Glads’ or ‘Sword Lilies,’ are popular additions to summer gardens known for their dramatic, upright flower spikes. These blooms grow from an underground storage organ, technically a corm, often mistakenly called a bulb. Achieving a sturdy display depends on mastering the correct planting technique and ensuring the corm is placed at the depth needed to support the plant’s eventual height.
Preparing the Planting Site
Gladioli thrive in full sunlight, requiring a minimum of six to eight hours of direct sun daily for the best stem strength and flower color. Planting should occur in the spring, after the danger of the last hard frost has passed and the soil has warmed up. Successive planting, setting corms every two weeks until early summer, ensures a continuous bloom period.
The composition of the soil is important, as gladioli corms are susceptible to rot if they sit in wet conditions. Soil must be well-draining. If the existing soil is heavy clay, amend it by thoroughly mixing in well-rotted compost, aged manure, or coarse sand to improve drainage and aeration. This helps create a fertile, loose medium for root establishment.
Determining the Correct Planting Depth and Spacing
The standard rule for planting gladioli corms is to place them four to six inches deep in the soil. This depth provides a solid anchor for the mature plant, which can grow tall and become top-heavy when in bloom. Planting too shallowly results in weak stems prone to toppling over. Set the corm into the prepared hole with its pointed side facing upward, as this is where the new shoot will emerge.
The exact depth can be adjusted based on soil type. In lighter, sandy soils, planting closer to six inches deep offers better stability and moisture retention. Conversely, in heavier, clay-based soils, a shallower depth of four inches is advisable for easier sprout emergence. Proper spacing is also crucial; individual corms should be placed approximately four to six inches apart for air circulation and nutrient access.
Essential Immediate Aftercare
Once the corms are positioned and covered with soil, the first step in aftercare is a deep, thorough watering. This initial soaking settles the soil around the corm, eliminating any air pockets that could cause the roots to dry out. Following this, the soil should be kept consistently moist throughout the growing season, especially once the sword-like sprouts appear above ground. However, consistent moisture does not mean soggy; overwatering can quickly lead to the corm rotting.
The height of many gladioli varieties necessitates providing support early on to maintain straight, upright growth. It is most effective to insert a sturdy stake or support structure near the corm at the time of planting, rather than waiting until the flower spike has formed. This prevents accidental damage to the corm later and ensures the plant has a guide as it grows taller. Applying a two-to-four-inch layer of organic mulch after planting helps to maintain soil moisture and suppress weed growth.