Bamboo is highly sought after for creating dense privacy screens, but its reputation for aggressive spread often causes concern. Successfully managing bamboo growth requires understanding the plant’s biology and implementing appropriate physical controls to contain the horizontal movement of its underground stems, called rhizomes. A proper containment strategy prevents the bamboo from invading neighboring areas and protects hardscapes like driveways and foundations.
Running vs. Clumping Bamboo
The first step in planning containment is identifying the type of bamboo you have, as this determines the level of intervention required. Bamboo falls into two main categories based on its rhizome structure: running and clumping. Running bamboo, known scientifically as monopodial, is the species that causes the most concern for spread. Its rhizomes are long and slender, vigorously extending horizontally through the soil before sending up new shoots or culms many feet away from the parent plant in a single season.
Clumping bamboo, or sympodial, is significantly less invasive and generally does not require intensive containment. Its rhizomes are short and thick, causing the plant to expand slowly outward from its center, usually only a few inches to a foot each year. They still require space to reach their full potential, and some larger varieties may need minimal shaping to prevent encroachment on nearby structures. Therefore, the most rigorous containment methods are primarily designed to manage the aggressive nature of running bamboo.
Installing Subterranean Rhizome Barriers
A permanent, physical barrier is the most effective method for containing running bamboo species. High-density polyethylene (HDPE) plastic is the preferred material, chosen over metal or concrete due to its flexibility and durability. The barrier material should have a minimum thickness of 40-60 mil, with 60 mil being recommended for most running varieties, and up to 80 mil for larger timber species.
Installation requires digging a narrow trench around the entire perimeter of the desired growing area. The depth of the barrier must be sufficient to prevent rhizomes from diving underneath, with 24 to 30 inches being a typical working range, as most rhizomes grow in the top 20 inches of soil. The trench should be approximately 28 inches deep, allowing a small portion to remain exposed above ground. This exposed section, or “lip,” must stand 2 to 4 inches above the soil line to force any upward-growing rhizomes to the surface, where they can be easily pruned.
When the barrier is installed, it must completely encircle the bamboo and remain vertical, avoiding any inward or outward angling that might direct rhizomes deeper. If multiple sections of barrier are required, the ends must be overlapped securely to prevent any escape points. A 12-inch overlap, secured with specialized stainless steel clamps and bolts, is necessary to form an impermeable seam. Backfilling the trench, first with the subsoil and then the topsoil, should be done carefully to ensure the barrier remains exactly vertical and no air pockets form.
Above-Ground and Manual Containment Methods
For smaller plantings or situations where a continuous underground wall is impractical, alternative containment strategies exist. Container planting is effective, especially for small spaces, but it restricts the bamboo’s mature size. Containers must be large and constructed from a sturdy, durable material like thick plastic or galvanized metal, and they should be monitored to ensure rhizomes do not escape through drainage holes.
Another manual approach involves creating an open trench around the bamboo’s perimeter, which serves as a visible boundary for the rhizomes. This trench should be 6 to 12 inches wide and deep, exposing the shallowly growing rhizomes when they attempt to spread. This method is non-permanent and requires annual or semi-annual maintenance, where any exposed rhizomes are cut back with a sharp spade and removed. While less labor-intensive initially than a barrier installation, this ongoing root pruning must be performed regularly to be successful, making it a high-maintenance choice for long-term control.
Essential Maintenance for Long-Term Control
Success depends on consistent maintenance and vigilance. For a subterranean barrier, the most important routine is monitoring the exposed lip throughout the year. Rhizomes that strike the barrier will be deflected upward, and they must be physically cut and removed whenever they appear above the soil line. Regular inspection of the soil immediately outside the contained area is necessary, particularly after heavy rain or freezing and thawing cycles, which can potentially shift the barrier. For all bamboo plantings, the prompt removal of new shoots, or culms, that appear outside the containment zone is an ongoing task. These new shoots should be pruned as soon as they emerge from the ground to prevent them from developing into mature canes and further expanding the root mass.