Cannas, often called “Canna Lilies,” are tropical and subtropical perennials closely related to ginger and bananas, not true lilies. They multiply vigorously. This natural tendency to proliferate is an inherent part of the plant’s growth cycle that requires management to maintain health and optimal flowering. Understanding how they grow underground is key to successful cultivation.
Vegetative Multiplication via Rhizomes
The primary method of multiplication occurs underground through a specialized structure called a rhizome. A rhizome is a thick, fleshy, modified stem that grows horizontally beneath the soil surface. It serves as a storage unit for starches and proteins, providing the energy reserves the plant needs to survive dormancy and initiate new growth.
During the growing season, the mother rhizome continuously produces lateral offsets, often called “eyes” or buds, along its length. These dormant growth points activate to develop into new shoots and root systems, forming genetically identical daughter plants. This process rapidly develops the original single rhizome into a dense, interconnected clump. Because this aggressive growth leads to a crowded root system, periodic division is necessary to prevent overcrowding and maintain robust flowering.
Practical Guide to Dividing Canna Clumps
Managing vigorous growth involves physically dividing the congested clumps. This is best done in early spring before substantial new growth, or in late fall after the foliage has died back. Begin by carefully lifting the entire clump of rhizomes from the soil using a garden fork or spade. Gently remove the soil, often by rinsing, to expose the network of rhizomes and their growth points.
To create new, viable plants, separate the rhizome mass so each new section contains at least one, but preferably two or three, visible “eyes” or buds. While sections can sometimes be broken apart by hand, a sharp, sterilized knife is often required for denser connections. After division, allow the cut surfaces to dry for a day to form a protective layer, which helps prevent rot. Replant the new sections horizontally, about four to six inches deep, and water thoroughly to establish them.
Multiplication Through Seed Production
While rhizome division is the most common method, Cannas also reproduce sexually through seeds. After the flowers fade, the plant produces round, spiky seed pods that reveal hard, black, pea-sized seeds. This propagation method is significantly slower than vegetative division and introduces genetic variation.
Unlike plants grown from rhizomes, which are clones, seed-grown plants may not “come true” to the parent, displaying different characteristics. The seeds possess an extremely tough, impermeable outer coat that prevents water absorption and delays germination. To successfully sprout them, the seeds require scarification, where the hard coat is nicked or softened by soaking in warm water for 24 hours or more.