Crocosmia Propagation

Crocosmia grows as a hardy summer flowering plant in USDA hardiness zones 6 through 10, but they cannot tolerate prolonged temperatures below 20 degrees Fahrenheit. The plants survive in the garden for many years, reproducing underground. Propagation requires nothing more than the tools to dig up the crocosmia flowers for division.

Corms and Propagation

• Similar to a flower bud, a corm collects the nutrients and energy during the growing season that help fuel the following year’s blooming period. The corm sits at the top of the root system as a swollen part at the bottom of the stem. Crocosmia corms reproduce underground, with new corms forming at the top of the old one and small cormels, also called offsets, developing around the side. The new corm forms to fuel the existing plant, while the smaller cormels eventually develop into new corms that grow into new plants.

Division Time

• Crocosmia cormels take two to three years to become mature enough to produce a flowering plant. Those separated from the mother corm before maturity still grow foliage, they just do not flower until they reach mature size. Dividing every two to three years not only supplies you with new plants, it prevents the crocosmia bed from becoming overcrowded. Division takes place in spring right before or just after the last expected frost date and before the crocosmia begins putting on new growth. Marking the location of the corms in fall makes finding them in the bed simpler when they are still dormant in spring.

Propagation Methods

• Using a garden fork to loosen the soil around the crocosmia corms allows you to lift them from the soil without the danger of spade damage to the corms. The old corm sits beneath the plump new corm and the cormels grow from the side of these two corms. Corms and cormels easily snap apart, allowing you to dispose of the old corm since it’s no longer productive. If the crocosmia produced an abundance of cormels, the larger ones are closer to blooming and the smaller ones can be planted or disposed of, depending on how many plants you desire.

Planting Divisions

• Crocosmia corms grow in full-sun garden beds that provide a well-drained soil bed. Standing water causes corms to to rot. Replanting occurs immediately after dividing and the mature corms bloom the first year after propagation. Setting the corms in the soil so the top sits 3 inches beneath the soil surface and spacing each corm 6 to 8 inches apart in all directions gives the crocosmia the room it needs to grow and room for the new corms to begin producing their own offsets.