Bamboo, a member of the grass family Poaceae, is often introduced into landscapes for its fast growth and screening capabilities, but its root system can be highly invasive. The potential for a bamboo plant to spread aggressively is determined by the structure of its underground stems, known as rhizomes. Running bamboo species are designed for rapid and far-reaching colonization, making them a significant concern for property owners. Clumping bamboo varieties spread at a much slower rate and pose a minimal threat to surrounding areas. Understanding the specific type of rhizome structure is the first step in managing or preventing bamboo encroachment.
Understanding Running Versus Clumping Varieties
The primary distinction between bamboo types lies in their rhizome morphology, which dictates the plant’s growth pattern. Running bamboos are classified as monopodial, meaning their rhizomes are long, slender, and grow horizontally underground, often traveling a considerable distance from the parent plant. This leptomorph rhizome system is characterized by buds at each node along the underground stem, which can develop into either a new rhizome to continue spreading or a new aerial shoot, called a culm, to emerge above ground.
Running bamboo species, such as those in the Phyllostachys genus, colonize new territory aggressively. In a single growing season, these rhizomes can extend up to 20 feet or more away from the original planting. This lateral spread results in a scattered, open grove where new culms appear individually across a wide area. Running bamboo can quickly become invasive if its movement is not physically restricted.
Clumping bamboos, by contrast, possess a sympodial rhizome system, also known as pachymorph. These rhizomes are shorter, thicker, and grow in a tight, U-shaped pattern, curving upward shortly after emerging from the parent plant. A new culm only forms at the very tip of the rhizome, which causes the dense, compact growth habit characteristic of clumpers.
Species in the Fargesia or Bambusa genera are examples of this clumping habit, which expands only by a few inches annually. The concentrated growth keeps the culms clustered closely together, minimizing the risk of unwanted spread. Clumping bamboo is considered non-invasive, making it a safer choice for small yards or areas near property boundaries.
Essential Strategies for Containment
For running bamboo that is already established or desired in a landscape, proactive containment is necessary to prevent its spread. The most effective method is the installation of a physical rhizome barrier, which redirects the rhizomes to an area where they can be managed. The barrier should be made of high-density polyethylene (HDPE) plastic, typically 40 to 80 mil thick, and buried to a depth of 24 to 30 inches.
Crucially, the barrier must protrude approximately two inches above the soil line to intercept rhizomes that might try to arch over the top. Some installation methods recommend angling the barrier slightly outward to encourage any contact rhizomes to grow upward, making them easier to spot. Regular maintenance involves inspecting the exposed edge of the barrier once or twice a year to cut and remove any rhizomes attempting to escape over the top.
An alternative strategy is annual root pruning, especially for bamboo planted without a full barrier. Running bamboo rhizomes typically grow shallowly, often within the top 2 to 5 inches of soil, making them accessible. Using a sharp, straight-edged spade, a gardener can cut the spreading rhizomes around the perimeter of the desired grove.
Root pruning should be performed bi-annually, ideally during the growing season, to sever the tips of the expanding rhizomes. In areas bordered by a lawn, simply mowing the perimeter frequently during the spring shooting season can effectively control new culms by knocking them over. This continuous mechanical removal starves the underground system of the energy needed to establish new growth outside the designated area.
Eradication and Structural Concerns
Unchecked running bamboo can cause significant structural problems due to the unrelenting pressure exerted by its expanding rhizome network. The sharp, pointed rhizomes are known to exploit existing weaknesses, growing into cracks in concrete patios, driveways, and retaining walls. While the rhizomes are unlikely to penetrate a solid, modern foundation, they can easily travel underneath a structure and emerge through small gaps in floorboards or cavity walls.
The extensive root system can also interfere with underground utility lines, such as drainage pipes, where the bamboo searches for moisture. Complete eradication of an established grove requires a persistent, multi-year effort that focuses on depleting the massive energy reserves stored in the rhizomes. Non-chemical removal involves cutting all culms to the ground and then diligently removing any new shoots that emerge, which must be repeated until the rhizomes are fully exhausted.
For chemical eradication, a systemic, non-selective herbicide like glyphosate is the most common approach. The most effective method is the cut-stump application, where the culms are cut near the ground and a concentrated herbicide solution is immediately painted or sprayed onto the fresh cut. This direct application ensures the chemical is quickly absorbed and translocated down into the rhizome system.
A high concentration of glyphosate, often 40% or higher, is typically used for this method. The application must occur within minutes of cutting because the bamboo stem seals over rapidly, preventing the herbicide from entering the vascular system. Multiple treatments over several seasons are necessary to achieve complete control and prevent regrowth from deep or dormant rhizomes.