The keyword “invasive” is frequently associated with bamboo because of its aggressive growth habits, leading to confusion among US homeowners seeking fast-growing screening properties. The term can be misleading since not all varieties pose a threat to the landscape or neighboring yards. This aggression depends entirely on the specific type of bamboo planted. The issue focuses on certain varieties that rapidly colonize new ground, rather than a blanket condemnation of the entire plant family.
Understanding the Two Types of Bamboo Growth
The reputation bamboo has gained for being difficult to control is primarily due to a specific growth pattern known as “running,” characteristic of species in the genus Phyllostachys. This type of bamboo spreads unpredictably and rapidly because its underground structure is designed for extensive colonization. Running bamboo is the main source of the “invasive” reputation, as it can quickly spread far from the original planting site and emerge in unwanted areas.
In contrast, “clumping” bamboo, often from the genus Fargesia, is considered non-invasive. These varieties have a short, compact growth habit that expands slowly, typically only a few inches to a foot annually. Clumping bamboo is safer for residential gardens because it naturally stays in a circular clump. It is a suitable choice for small spaces, as its growth is contained without the need for extensive physical barriers.
The Mechanics of Underground Spread
The aggressive spread of running bamboo is driven by its specialized underground stems, called monopodial rhizomes, which are long and thin. These structures act as horizontal runners, extending outward from the parent plant and producing new shoots along their length. This allows running bamboo to travel several feet in a year, enabling it to breach typical garden boundaries and emerge far from the original grove.
In contrast, clumping varieties utilize sympodial rhizomes, which are short and thick, with a U-shaped structure that curves upward almost immediately. This growth pattern results in the new growth staying tightly clustered near the base of the existing plant. While most bamboo rhizomes grow in the top 12 to 18 inches of soil, the depth of spread can be influenced by soil conditions. The monopodial system’s ability to send out long, horizontal rhizomes makes it difficult to manage and prone to appearing unexpectedly in a neighbor’s yard.
Containment and Control Strategies
Preventing the spread of running bamboo requires the installation of a specialized physical barrier, which acts as a vertical wall to deflect the traveling rhizomes. This barrier, typically made of high-density polyethylene (HDPE) plastic in a thickness of 40 to 80 mil, must be installed in a trench. For most varieties, the barrier should be placed at least 24 to 30 inches deep to intercept the rhizomes. The barrier must protrude about two to four inches above the soil line because bamboo rhizomes are inclined to “jump” or grow over a barrier that is flush with the ground.
Eradication and Legal Issues
For existing infestations, eradication requires a multi-year, intensive program that aims to deplete the plant’s stored energy. The physical removal process begins with cutting all above-ground stalks, or culms, down to ground level. Following this, continuous mowing of any new shoots that emerge can eventually starve the underground rhizome system, with noticeable results often taking two to three years.
Chemical control is an option, often involving non-selective herbicides containing glyphosate, which is applied to the new leaves or freshly cut stems. For this method to be effective, the bamboo must be allowed to regrow until the new leaves have fully expanded before the herbicide is applied, allowing the plant to absorb the chemical and transport it to the rhizomes.
The aggressive nature of running bamboo has also led to legal complications, as its spread onto a neighbor’s property may be considered a private nuisance or trespass in many jurisdictions. Homeowners can be held liable for the cost of removal and any damage caused, making proactive containment or complete removal a prudent measure.