Bamboo is often perceived as a single plant, but it is a giant woody grass belonging to the grass family Poaceae and the subfamily Bambusoideae. This subfamily contains a vast collection of different plants, with estimates ranging from over 1,400 to 1,852 distinct species across more than 115 genera worldwide. Understanding the classification of bamboo is necessary for proper selection and landscape management due to its variety in growth patterns, size, and hardiness.
The Primary Classification: Running Versus Clumping Rhizomes
The most significant difference among bamboo types lies in their underground structure, specifically the rhizomes, which determine how the plant spreads. These underground stems are categorized into two primary growth habits: running and clumping. This distinction dictates the plant’s invasiveness and necessary containment.
Running bamboos (leptomorph or monopodial) develop long, slender rhizomes that aggressively spread horizontally beneath the soil. These rhizomes can travel a substantial distance from the mother plant before turning upward to produce a new culm, or cane. The genus Phyllostachys, which includes popular varieties like Golden Bamboo, is a common example of this fast-spreading type.
Because of their invasive nature, running bamboos require proactive containment measures to prevent them from overtaking a garden or property line. The most effective method is installing a non-degrading, subsurface barrier, typically made from high-density polyethylene (HDPE). This barrier should be at least 60 to 80 mil thick and sunk 30 to 36 inches deep.
Two inches of the barrier must protrude above the soil line, preventing the rhizomes from growing over the top. The barrier deflects their path upward, allowing them to be easily pruned or managed. Without such a barrier, the plant’s spread can be rapid and challenging to control, leading to the plant’s reputation for being difficult.
In contrast, clumping bamboos (pachymorph or sympodial) have short, thick, U-shaped rhizomes that grow in a tight, dense mass. These rhizomes immediately curve upward to produce a new culm very close to the original plant. The genus Fargesia (fountain bamboo) and many species of Bambusa are examples of this non-invasive habit.
Clumping varieties typically expand their base only a few inches each year (usually between 2 and 12 inches), making them manageable in smaller landscapes without a root barrier. They form a tight cluster but do not send out aggressive runners, making them preferred for ornamental planting. The distinction between running and clumping is the single most significant factor in managing bamboo growth.
Diversity in Appearance: Size, Color, and Leaf Structure
Beyond the underground differences, bamboo species exhibit morphological variations in their above-ground appearance, or culms. These differences involve height, diameter, color, and texture of the cane itself. The spectrum of size variation ranges from dwarf groundcover varieties to towering timber species.
Dwarf bamboos, such as those in the genus Sasa, may only reach heights of one to two feet, functioning as a dense, low hedge or groundcover. Conversely, giant timber bamboos, like certain species of Dendrocalamus, can grow over 100 feet tall with a culm diameter exceeding six inches. The mature size of the culm is fixed when it emerges from the ground, expanding only in height, not width, during its lifespan.
Culm color and texture present a wide array of visual traits. While most varieties are green, others display striking colors, such as the jet-black culms of Phyllostachys nigra or the bright yellow canes of Phyllostachys aurea. Some species, like Tropical Blue Bamboo (Bambusa Chungii), have a waxy coating that gives the canes a distinct blue hue. Others may feature striped patterns or a square-like shape.
Leaf characteristics further contribute to the visual diversity, varying in size, density, and variegation. Most bamboo leaves are lance-shaped, but their arrangement and size create different textures. Some clumping varieties, such as Fargesia, have small, delicate leaves that create a graceful, weeping appearance. Others have large, dense foliage ideal for creating thick privacy screens.
Practical Applications and Regional Suitability
The choice of bamboo type is influenced by its intended use and the specific environmental conditions of the planting location. A primary consideration is hardiness, which separates tropical and temperate bamboos. Tropical varieties, such as many species of Bambusa, are sensitive and will not survive temperatures at or near freezing.
Temperate bamboos are cold-hardy and can withstand freezing temperatures, with some species surviving in USDA Hardiness Zones as low as 5, enduring temperatures down to -20 °F (-29 °C). While these varieties may lose their leaves or entire above-ground growth during a severe winter, the underground rhizome system often survives to send up new shoots in the spring. Understanding the specific temperature tolerance of a species is necessary to ensure its survival outside of its native range.
Beyond climate, different bamboo types are selected for specific applications. Large timber bamboos, including Dendrocalamus and certain Phyllostachys species, are grown for their sturdy culms used in construction, furniture, and flooring. They are harvested when the culms are several years old and have reached peak strength and density.
Other species are cultivated for their edible shoots, a common ingredient in many Asian cuisines, with the young shoots of certain Phyllostachys varieties being particularly sought after. For privacy screening and ornamental purposes, dense-foliage types like Fargesia robusta are often chosen for their upright growth habit and non-invasive nature. The vast differences in structure, hardiness, and yield mean that the selection process is driven by both function and the local climate.