Bamboo Biology - Behavior and Traits
Bamboo Biology - Article Contents
- Taxonomy and Classification
- Morphology, Structure, and Anatomy
- Bamboo Behaviors
- Runners vs. Clumpers
- The Bamboo Flower
The Behavior of Bamboo
In their most basic form, bamboos are evergreen tree-like grasses with woody stems. It is difficult to precisely describe the growth characteristics of bamboo because its behavior is dependent on the local conditions of the growing site. A bamboo growing in ideal conditions can look and behave much different from a bamboo growing inadequate conditions. In this section we describe the behaviors that are most important to consider when growing bamboo.
The most distinguishable characteristic of bamboo is the root system, which is comprised of a group of rhizomes. Rhizomes are stems that migrate from the central plant to establish new territory. As the rhizomes spread underground, they will eventually travel upwards to create a new culm. This process takes place each year and is observed when new shoots becomes visible arising from the soil. Depending on the variety of bamboo and growing conditions, this normally observed in the spring season. The behavior of rhizomes is put into two distinct categories, running and clumping.
Running Bamboos (Monopodial) – Running bamboos are characterized as having self-propagating rhizomes which travel underground, and eventually breech the surface to create a Culm. The rhizomes travel horizontally, and have the ability to move through 20 feet of soil in a single season. The direction and distance of rhizome growth is unpredictable. They are most commonly found naturally in temperate regions, with the most notable genera being Phyllostachys and Pleioblastus. Most varieties are cold hardy and are able to survive in below freezing temperatures. Running bamboos are invasive by nature and will spread rapidly if not controlled. This can be a problem when attempting to grow running bamboos in an isolated section of your garden. The most common remedy is to install a rhizome barrier around central plant stop the spread. Check out our article on rhizome barrier installation for more details.
Giant Running Bamboos can Spread Great Distances.
Clumping Bamboos (Sympodial) – Clumping bamboos are characterized as having upward curving rhizomes that grow off of each other. The rhizomes are thicker and shorter than those found in running bamboos, and lack the ability to spread over wide areas. They curve upwards and new culms can only form from the tip of the rhizome, which causes the culms to remain in close proximity to the central plant. This makes clumping bamboos the ideal choice for creating hedges and privacy screens. The most common genus is Bambusa and is primarily found in tropical regions. Clumping bamboos are generally less cold hardy than running bamboos and extra precautions must be taken if the plant will be exposed to frost and freezing temperatures.
Clumping Bamboo, Bambusa multiplex. (Photo: KENPEI)
Culms – Culms are the most visibly distinguishable feature of a bamboo plant. Culms can vary in size, shape, color, and even smell. The appearance can range from thick or thin, tall or short, erect or bent, and can exhibit irregular patterns such as those found in Tortoise Shell Bamboo (P. heterocycla f . heterocycla ‘Kiko’). Most culms are round in shape, but some species can take on a square like appearance. The color of the culms also has a wide range of characteristics. Although the majority of bamboos are green, they can also be brown, black, yellow, or striped. One of the most popular garden bamboos, Black Bamboo (Phyllostachys nigra), is unique in the fact that the culms exhibit a nearly jet black color. The culms can also very in smell. One of the most interesting examples is Incense Bamboo (Phyllostachys atrovaginata), which has a waxy coat on the culms that emits a pleasant fragrance similar to incense.
New culms will generally emerge in the springtime, however timing will vary among species. A new culm is very vulnerable to damage from the environment in the first several weeks after shooting. In fact, it takes nearly 3 growing seasons for most culms to become fully hardened. It is good practice to keep new culms protected from possibly destructive agents, such as wind or animals. It is also easy to accidentally step on top of a shoot within the first couple days of emergence. Extra care needs to be taken when walking near the bamboo during the weeks new shoots start to develop. A newly sprouting bamboo shoot will be covered by overlapping sheaths which are usually brown in color with a layer of fuzz. These sheaths help protect the soft outer tissue of the culm and provide the hormones necessary for rapid growth. Growth of the culm will be inhibited if these sheaths are removed. Eventually they will fall of naturally and can even be collected for use in an organic mulch mixture.
Moso Bamboo Culms.
Branches and Leaves – As the culm sheaths fall off, branches will start to grow from the nodes at each section of the culm. The timing and appearance of branches can vary substantially among the different genera. In many running bamboos, such as Phyllostachys, the branches will start to grow almost immediately after the protective sheaths fall off. In other bamboos, branches may not appear for an entire year. More than anything, the behavior of the branches serves as a method of identifying the species of bamboo. The behavior of branches and leaves rarely poses any problems for a cultivator.
Bamboo Leaves and Branches. (Photo: Erin Silversmith)