Crocosmia is a vibrant perennial flower that grows from an underground structure called a corm. These plants are appreciated for their brilliant, fiery-colored blooms that appear in summer and their attractive, sword-like foliage. Transplanting becomes necessary either when you want to move the plant to a new location or, more commonly, when the corms become severely overcrowded. If left unchecked, this congestion can lead to a noticeable reduction in the number and size of flowers produced.
Identifying the Best Time for Transplanting
The success of moving Crocosmia depends on catching the plant during its dormant cycle to minimize transplant shock. The optimal window for lifting and transplanting the corms is either in late autumn or in early spring. Transplanting in late autumn should happen after the foliage has naturally died back and yellowed, signaling that the plant has stored its energy for the winter.
The alternative, and often preferred, time is early spring, just before the first new green shoots begin to emerge from the soil. Moving the corms during this dormant period ensures that the plant is not actively putting energy into leaf or flower production, allowing all resources to be focused on root establishment in the new location. In either season, the soil should be workable and not frozen or waterlogged for the best results.
Preparing and Dividing Crocosmia Corms
The first physical step is to dig up the entire clump, which often requires a strong garden fork due to the density of the corms. Insert the fork a good distance away from the stems to avoid slicing through the corms, then gently lift the entire mass from the soil. Once the clump is out, carefully shake or brush away the excess soil to expose the network of corms and their attached roots.
Crocosmia corms grow in vertical chains, requiring gentle separation into individual, viable corms, a process known as division. Focus on keeping the newest, firmest corms, which are usually the largest and located near the top of the chain. Discard any corms that feel soft, mushy, or completely dried out, as these are spent mother corms that will not produce new growth.
Trimming is a beneficial step; use clean shears to trim the roots to a few inches in length and cut back any remaining foliage to a short stump. This reduction in both root and leaf mass minimizes the water demand on the newly planted corm, allowing it to concentrate on generating new feeder roots. The most vigorous plants will grow from the top two or three corms in the chain, so prioritize these for replanting.
Replanting for Long-Term Success
The new planting site should be chosen with care, aiming for a location that receives full sun to partial shade, as ample sunlight supports the best flowering. Crocosmia thrives in fertile, moist, but well-draining soil, so heavy clay or constantly waterlogged areas should be avoided. Before planting, amend the new bed by incorporating organic matter, such as well-rotted compost, to improve both drainage and nutrient retention.
For planting, the divided corms should be set with the pointed end facing upward, typically at a depth of about three to five inches. Spacing the corms correctly is important to prevent rapid re-crowding, with a distance of four to six inches between each one generally recommended. Planting them individually, rather than in large clumps, will help delay the need for the next division cycle, which is usually required every three to five years.
Immediate and thorough watering is necessary after replanting to settle the soil around the corms and eliminate any air pockets. Following the initial watering, a layer of organic mulch, such as wood chips or straw, should be applied over the entire planting area. This mulch helps to maintain a consistent soil temperature, conserves moisture, and protects the shallowly planted corms from extreme temperature fluctuations as they establish.