Gladiolus, often called “glads” or “sword lilies,” are striking flowering plants that grow from a specialized underground storage organ known as a corm. Unlike true bulbs, a corm is a solid, swollen stem base that stores food to fuel the plant’s growth and survival during dormancy. Gardeners often need to relocate these plants due to soil depletion, which occurs if they are left in the same spot for more than two years, or because of overcrowding from new corms that develop annually. Moving the gladiolus is also necessary in colder climates where the corms must be lifted from the ground and stored indoors to prevent them from freezing over winter.
Optimal Timing for Relocation
The appropriate time to move a gladiolus is when the plant is in its dormant phase, which minimizes the stress of relocation. This period occurs either in the fall, after the growing season, or in the very early spring, before active growth begins. In cold regions, corms must be lifted in the autumn, typically after the first light frost has caused the foliage to yellow and die back naturally. Waiting for this dieback is important because the plant actively moves its stored energy and nutrients from the leaves down into the corm.
The foliage should be cut back to about one to two inches above the corm once it has yellowed, and the corms should be dug up before a hard freeze occurs. For replanting, the best window is in early to mid-spring, once the threat of hard frost has passed and the soil has become workable and warm enough to encourage root development. Replanting in spring allows the corm ample time to establish a robust root system before it begins to send up its tall flower spike later in the summer.
Preparing the Corms and New Site
Selecting the new location requires attention to the gladiolus’s need for maximum sunlight, which directly influences the size and color intensity of the blooms. Choose a spot that receives a minimum of six to eight hours of direct sun each day. The site should also offer some protection from strong winds, which can easily topple the plant’s tall flower spikes once they emerge.
Soil preparation is equally important, as gladioli require excellent drainage to prevent the corms from rotting. If the existing soil is heavy clay, it should be amended with well-decomposed organic matter such as compost or aged manure to improve its texture and nutrient content.
After the corms have been lifted from their old site, they need cleaning and inspection before they are stored or replanted. Brush off any excess soil and carefully remove the papery outer husks to check the corm surface for signs of disease or damage. Healthy corms should be firm and free of dark spots; discard any that feel soft or mushy.
Corm Treatment
Some gardeners choose to apply a commercial fungicide dust or a soak to the corms before planting to protect them from overwintering pests, like thrips, or common soil-borne pathogens. Separating the small cormlets that form at the base of the main corm is also part of preparation; these smaller divisions can be grown separately to produce new flowering plants in future seasons.
Step-by-Step Transplanting Process
The process of lifting an established gladiolus requires careful technique to avoid damaging the corm. Use a garden fork, rather than a spade, to gently loosen the soil in a wide circle, approximately six to eight inches away from the base of the stalk. Once the soil is loose, lift the entire plant from the ground, taking care not to pierce the corm with the fork tines or tear the roots.
If the plant is actively growing, handle it by the stem close to the corm to prevent the stalk from snapping or being crushed. For corms being replanted directly, or those coming out of storage, dig a trench or individual holes for planting. The goal is to plant the corms at a depth of four to six inches, with larger corms benefiting from the deeper end of that range for stability.
Spacing is a significant factor in preventing disease and ensuring healthy air circulation, so place the corms at least six to eight inches apart from one another. The corm must be oriented correctly in the soil, with the pointed end, which contains the developing sprout, facing upward toward the soil surface. After placing the corm, gently backfill the hole with the prepared soil, taking care not to leave large air pockets around the corm.
Lightly firm the soil over the planting area with your hand or the back of a rake to ensure good contact between the corm and the surrounding earth. In heavy or windy soils, planting the corms deeper, closer to six inches, provides natural support. This deep planting helps anchor the tall flower spikes against environmental movement and reduces the need for staking later in the season.
Post-Transplant Care
Immediate and thorough watering is necessary right after the corms are placed in the ground to help settle the soil and eliminate any remaining air pockets. For the first few weeks following transplantation, keep the soil consistently moist, but avoid saturating the area, which could lead to corm rot. The focus during this initial period is on encouraging the development of strong, new roots.
Once the plant begins to show significant growth, switch to a deep watering schedule of approximately once or twice a week, depending on rainfall and the soil’s ability to retain moisture. When the plant reaches about six inches in height, or as the flower spikes begin to emerge, apply a balanced, slow-release fertilizer. Fertilizers with a higher potassium content can support robust flowering, but those with excessive nitrogen should be avoided as they promote lush foliage at the expense of bloom production.
As the gladiolus grows, especially the taller varieties, monitor the plants for signs of instability. Staking may be required to protect the heavy flower spikes from being bent or broken by wind or rain. Drive a stake into the ground several inches away from the corm to prevent damage, and gently tie the main stalk to the support structure. Consistent monitoring for pests, particularly thrips, and signs of disease will help ensure a successful establishment and a season of healthy blooms.