Bamboo, a member of the grass family, is one of the fastest-growing plants on Earth. Propagation is the process by which the plant creates new individuals, typically resulting in clones of the parent stock. This asexual reproduction allows for consistent characteristics in the offspring. Understanding the vegetative structures that facilitate this growth is key to cultivating or controlling bamboo.
The Biological Engine: Rhizome Systems
Bamboo’s unique growth pattern and ability to spread are controlled by its underground stems, called rhizomes. These rhizomes function as energy storage organs and are the source of all new shoots and roots, driving the plant’s propagation. The morphology of these rhizomes dictates whether a species will be a “clumping” or a “running” bamboo, a distinction crucial for cultivators.
The two primary types of rhizome systems are pachymorph and leptomorph. Pachymorph rhizomes are short, thick, and curve upward near the parent plant, resulting in clumping bamboo. These rhizomes produce new culms, or aerial stems, only at their tips, keeping the new growth close to the existing cluster and forming a tight, manageable clump.
Leptomorph rhizomes, by contrast, are long, thin, and grow horizontally. These rhizomes have an indeterminate growth pattern, and buds along their length can form new culms or new rhizomes. This mechanism is responsible for the aggressive, spreading nature of running bamboo and enables it to colonize new territory quickly.
Propagating Through Rhizome Division
The most reliable and common method for propagating established bamboo is through the division of the rhizome systems. This technique isolates a portion of the parent plant’s underground structure, creating a complete, self-sustaining clone. The best time to perform this division is in the early spring, just before the new growth season begins, when the rhizomes’ food reserves are at their peak.
To successfully divide a plant, a healthy section of the rhizome, known as an offset, must be carefully separated from the main clump. This section needs to include a portion of the rhizome, a viable root mass, and at least one culm or bud. For running bamboo, a sharp spade can be used to sever the connecting rhizomes spreading away from the main grove.
Clumping bamboo is more difficult to divide because of its compact structure, often requiring a saw or axe to separate the dense mass. Once the division is removed, it should be immediately planted in its new location at the same depth it was previously growing, or potted in a well-draining medium. The new offset must be kept well-watered and protected from intense sun until it establishes new roots and shows new growth.
Propagation Using Cuttings and Seeds
Alternative methods like using culm or branch cuttings are employed, especially for certain clumping species. Cuttings involve taking sections of the main stem (culm) and inducing them to root, a process often easier with tropical clumping varieties. A culm cutting typically consists of one or two nodes, which are the ringed sections on the stem where new growth originates.
Success rates for cuttings are often lower than rhizome division, requiring careful preparation like trimming branches and ensuring the cutting is kept moist and warm. Cultivators may fill the hollow internode with water or treat the nodes with a growth-regulating substance to enhance rooting. Root development from cuttings takes several weeks, and the resulting plant is initially less vigorous than a rhizome division.
Propagation from seed is the least common method because bamboo flowering is a rare and unpredictable event, sometimes occurring only once every few decades. When seeds are available, they generally have no dormancy period and can germinate quickly. However, the difficulty in sourcing viable seeds and the extended time required for a seedling to develop a robust rhizome system make this method impractical for most cultivation efforts.