Calla lilies (Zantedeschia species and hybrids) are popular garden plants known for their elegant, trumpet-shaped blooms and lush, glossy foliage. These graceful perennials readily multiply, naturally increasing their presence over time. While often mistakenly referred to as growing from a bulb, Calla Lilies originate from a fleshy, underground structure called a rhizome. This unique underground stem structure is the mechanism responsible for the plant’s propagation and allows gardeners to easily expand their collection.
How Calla Lilies Multiply
The multiplication of the Calla Lily is a natural vegetative process driven by its rhizome, which functions as a storage organ for starches and nutrients. This main rhizome grows horizontally beneath the soil surface, similar to a ginger root. As the plant matures, the primary rhizome begins to produce smaller, lateral offshoots, known as offsets or daughter rhizomes.
These smaller offsets are genetically identical clones of the parent plant and develop their own distinct root systems and foliage over time. They remain physically attached to the original rhizome, leading to a dense cluster of plants. This continuous production of daughter rhizomes is the plant’s natural method of forming a larger, more robust clump, effectively multiplying the number of growing points each season.
Recognizing Overcrowding and Timing Division
Although multiplication is a sign of a healthy plant, the continuous production of new rhizomes eventually leads to overcrowding, which necessitates intervention. When too many plants compete for the same limited space, water, and soil nutrients, the overall health of the clump begins to decline. Gardeners should watch for clear signs of this stress, such as a noticeable reduction in the size and number of flowers produced.
The foliage may also appear stunted or less vigorous, and the visible clumping of stems will become very dense, leading to poor air circulation. This lack of airflow can increase the risk of fungal diseases and rot, especially in the moist conditions Calla Lilies prefer. To revitalize the plants and encourage vigorous blooming, division becomes necessary, typically every three to five years.
The timing for dividing the rhizomes is important to minimize stress on the plant. The best time to intervene is when the Calla Lily has entered its dormant phase, as its energy is stored underground and active growth has ceased. For most varieties, this occurs in the late fall after the foliage has died back, or in the early spring just before new shoots begin to emerge. Dividing the plant during its active growth cycle can significantly shock the system and compromise flower production.
Practical Steps for Dividing Rhizomes
Once the Calla Lily clump is dormant, the first step is to carefully dig up the entire cluster using a garden fork, working well outside the perimeter of the foliage to avoid damaging the roots. After lifting the mass, gently brush or rinse away the excess soil to clearly expose the network of rhizomes. At this point, you can identify the main rhizome and the smaller offsets attached to it.
The offsets can often be separated from the parent rhizome simply by hand, peeling them away where they are loosely joined. If the rhizomes are tightly bound, use a sharp, sterilized knife to cut the clump apart. Ensure that each new section retains at least one visible “eye,” which is the small growth bud where new foliage will emerge. Sections without an eye will not grow into a new plant.
After separating the rhizomes, allow the fresh, cut surfaces to dry out for one to two days in a warm, shaded area. This process, known as “curing” or “callusing,” forms a protective layer over the wound, guarding against soil-borne pathogens and moisture-related rot. Once cured, replant the divisions immediately, buried three to four inches deep with the growth eyes facing upward.