Bamboo is a catch-all name for many plants that have woody, hollow, jointed stems or canes and narrow leaves. Bamboo genera are part of the Graminaea or grass family and the Bambusoideae or bamboo subfamily. The most common Bambusoideae genera are: Arundinaria, Bambusa, Chimonobambusa, Dendrocalamus, Phyllostachys, Pseudosasa, Sasa, Semiarundinaria and Shibataea. Of that group, Phyllostachys is probably the most frequently grown in temperate climates. Bamboos are divided into two types, according to root structure: clumping and running.
Clumping bamboo is also referred to as "sympodial" genera. These plants have relatively short roots.that expand rather slowly--only an inch or so per year. The roots form discrete clumps, expanding annually as new culms or stalks sprout. Clumping bamboo generally does not expand as fast as running bamboo, but the plants are often--but not always--less cold-tolerant. The popular Fargesia is an example of a cold-tolerant, clumping bamboo. Another popular clump-forming genus is Phyllostachys.
Running bamboo plants, also referred to as "monopodial," spread rapidly by sending out rhizomes beneath the soil that produce new plants, sometimes at a distance from the original bamboo. These bamboos are useful when there is a great deal of ground to cover or the gardener wants a quick screen. Species of the genus Sasa, which also features unusually large leaves, are among the running bamboo and were popular in Victorian times.
Unlike many other grasses, both clumping and running bamboo genera flower rarely--sometimes only once in a century. In some bamboo species, the flowers have never been seen. The majority of plants in a single species flower within a single period lasting a few years. Flowering leads to seed-setting, but also weakens the plants, sometimes enough to kill them. Many Chusquea bamboo flowered in the 1990s. Yushania bamboo plants flowered most recently in the 1960s. Prior to that, the Yushanias last flowered around 1910.
Containing Running Bamboo
Running bamboo is notoriously difficult to contain. To keep it from overwhelming the rest of the garden, plant in large tubs sunk 3 feet in the ground and prune top growth aggressively every other year. Alternately, plant by water, as the roots will not tolerate being waterlogged. Some gardeners contain bamboo by installing a specially designed rhizome barrier, or by pouring concrete or gravel into a 3-foot-deep trench around the bamboo. The material in the trench should stop 1 inch short of the top of the trench to make it easier to grub out stray rhizomes.
Bamboo can be removed by digging out entire clumps or groups of plants. If some plants are to be retained, it may be necessary to split clumps with heavy, sharp tools. Unwanted clumps or colonies of running bamboo can also be eradicated with a systemic herbicide in a phased process that involves cutting down the existing canes, waiting until new growth appears and treating the growth with the herbicide. Herbicide application may have to be repeated when or if new shoots appear.