Bamboo is  a generic term for a large number of different plants, typically perennial, evergreen, woody-stem grasses that are among the fastest-growing plants in the world. Bamboo is generally categorized into two types: clumping and running. The plant's type of rhizome, or underground stem, determines its classification. Bamboo plants have above-ground stems, called culms, and underground rhizomes. These rhizomes come in two types--pachymorph and leptomorph. 

Pachymorph rhizomes are characteristic of clumping bamboo. These rhizomes always turn upward and develop into a culm. They are usually curved, with the maximum width of the rhizome slightly thicker than the above-ground culm it becomes. More rhizomes emerge from buds on existing rhizomes. A preferred clumping type of bamboo, Fargesia, is hardy in north America.

Clumping bamboo is relatively slow in spreading. Its root system can compete with surrounding plants, but it can usually be removed by digging up the offending plants.

Leptomorph rhizomes, on the other hand, are difficult to control. Smaller in diameter than the culms that originate from them, these rhizomes run laterally underground. The buds usually remain dormant, but those that germinate may produce either rhizomes or culms. These newly created rhizomes in turn also run laterally underground, in turn creating more culms and more new rhizomes. This rapid, hardy lateral growth is highly resistant to containment.

Leptomorph rhizomes are characteristic of running bamboo.  Some of the most commonly known running bamboos are Phyllostachys bamboos. These are the classic bamboos that can reach up to 70 feet tall, with stems up to 6 inches wide. They are strong, fast-growing, spreading plants with varying degrees of hardiness in Zones 5-10

Bamboos with leptomorph rhizomes have two active growth periods. The first is the above-ground growth of the culms, usually in spring through the beginning of summer. The second is later in summer through fall. Warm weather and warm ground temperature create rapid growth, sending up new shoots to 90% of their full height in 30 days.

A newly planted running bamboo will grow slowly in the first couple of years of its life. But one spring you will find new culms springing up many feet away from the mother plant, and in subsequent years the larger plants will spread even further.

There are two methods of controlling the spread of running bamboo.

The first is containment, either by planting in a container or by sinking a vertical plastic barrier 30+ inches deep around the perimeter of the plant. Plastic is preferable to cement (which often develops cracks), or metal (which rusts and requires many seams), is less expensive, and lasts 20-30 years if installed properly. 

A barrier does not stop a running rhizome; it only deflects it. So the barrier should be slanted outward at the top, away from the bamboo at a 15-degree angle, so when the rhizomes hit it they will bend upwards. This should prevent the rhizome from growing down and under the barrier. The barrier should also project two inches above ground level to stop rhizome from going over. Check the barrier once a year in September or October and cut off rhizomes that arch over the top.

The second method is rhizome pruning, best done when the rhizomes are new. Unlike older woody rhizomes, new rhizomes (the late-summer growth phase) are rather tender and lack an extensive root system. Rhizome growth generally ceases between late fall and early spring. During this period, the new rhizomes, 1 foot or less beneath the surface, can be severed easily with a garden spade. Cut and remove them. Rhizome pruning should be performed annually.

For more detailed information on bamboo growth and removal, visit the Missouri Botanical Garden's information page.

For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service