Bamboo Roots Depth for Clumping and Running Varieties
A bamboo's underground growth is defined by its rhizome system. Learn how this distinction dictates its spread and informs effective garden management.
Bamboo is a popular garden plant, known for its rapid growth and architectural stems. However, this fast growth is also a source of concern for many gardeners who are curious about how the plant’s underground structures behave. Understanding the nature and depth of bamboo’s root system is a common starting point for anyone considering adding it to their landscape.
Understanding Bamboo Root Systems
The primary underground structure of a bamboo plant is not a true root system but a network of modified stems called rhizomes. These rhizomes are responsible for the plant’s ability to spread, storing the energy that fuels its rapid growth. The actual roots are fine, fibrous structures that grow from these rhizomes to absorb water and nutrients from the soil. The behavior of the rhizomes determines whether a bamboo is categorized as a “running” or “clumping” type.
Running bamboos possess a leptomorph, or monopodial, rhizome system. These rhizomes are long, thin, and grow horizontally, sending up new canes, called culms, from nodes along their length. This growth pattern allows them to spread over considerable distances from the parent plant.
In contrast, clumping bamboos have a pachymorph, or sympodial, rhizome system. These rhizomes are short, thick, and curve upwards to form a new culm very close to the original plant. This structure results in a dense, compact cluster of canes that expands slowly and predictably from a central point.
Root Depth of Running Bamboo
The aggressive nature of running bamboo is a primary concern for many gardeners. Its rhizomes are known for their vigorous horizontal spread, capable of traveling many feet in a single growing season to establish new culms. The rhizomes themselves are smaller in diameter than the culms they produce.
Despite their aggressive spread, the rhizomes of running bamboo are quite shallow. Most of their activity occurs within the top 6 to 18 inches (15 to 45 cm) of soil, and in many garden situations, they are found in the top 12 inches (30 cm).
Several factors can influence the depth of these rhizomes. In loose, well-drained, or fertile soil, the rhizomes may spread more vigorously but still tend to stay near the surface. If the plant is searching for water or nutrients, the rhizomes might push slightly deeper. Their ability to spread is also enhanced in moist conditions, which supports their extensive network.
Root Depth of Clumping Bamboo
Clumping bamboo offers a predictable and contained growth habit. Its rhizomes are stout, short, and curve upward, causing each new culm to emerge close to the parent plant. This growth pattern forms a dense, circular clump that expands slowly year after year.
The rhizome mass of clumping bamboo is generally shallow, with the roots growing near the surface at a depth of around 12 to 16 inches (30 to 40 cm). The fibrous roots that extend from these rhizomes may go deeper, between 12 to 20 inches (30 to 50 cm), to anchor the increasingly dense plant and absorb water. The rhizomes themselves, however, stay in a contained area directly beneath the visible canes.
Because of their dense and compact nature, the root systems of clumping bamboos can exert significant pressure on nearby structures as they slowly expand. While they are not invasive in the same way as running types, it is still a consideration to plant them at a distance from fences or foundations.
Managing Bamboo Root Growth
Managing the spread of bamboo is directly related to its rhizome behavior. For running varieties, the most effective method of containment is installing a rhizome barrier. Because the rhizomes are shallow growers, a barrier installed to a sufficient depth can successfully block their horizontal path.
A common material for this is a high-density polyethylene (HDPE) barrier, with a recommended depth of 24 to 30 inches for most running bamboos. The barrier should be installed in a trench surrounding the planting area and protrude about 2 to 3 inches above the soil surface to prevent rhizomes from growing over the top. Angling the barrier slightly outward at the top helps direct any rhizomes that hit it upward, making them easier to spot and prune.
Clumping varieties can also benefit from management when planted near property lines or structures. A shallow barrier dug 12 to 16 inches deep can be enough to guide the growth of a clumping type. Regular inspection of any barrier is good practice to prune any rhizomes that may have found a way around the containment system.