Bamboo: the easy exotic - includes growing directions and descriptions of varieties

You see, there was this street light...

It was one street over and shone right into my eyes when I stepped out onto my patio. Since shooting out street lights is frowned upon in my neighborhood, I needed something to block that light. The solution was a planting of punting pole bamboo (Bambusa tuldoides) that, by the following year, was hiding the street light behind its barrier of evergreen foliage.

Bamboo can serve as a centerpiece of tropical splendor, a fast-growing screen, a neutral background or a foot-high groundcover, depending on the species you choose and how you handle it. Its roots can bind soil to prevent erosion, its branches and leaves can provide cover for wildlife and its shoots can feed people - or pandas, if you happen to have any. What's more, it can do all these things quickly. Even in Northern climates, bamboo is about the fastest-growing of our large plants.

There are perhaps 150 cultivars of various bamboo species available as ornamentals in the United States. They range from 70-foot giants with woody stems 8 inches in diameter to foot-high miniatures, such as dwarf fernleaf bamboo (Arundinaria disticha), that you can mow like grass.

Bamboos aren't grown for their flowers. Their beauty comes from their form, their foliage and its contrast with the stalks, called culms. Some varieties have variegated, white-and-green leaves. Others have culms of green, black, gold or mottled patterns resembling snakeskin.

Botanically, bamboos are giant grasses. They spread by means of underground rhizomes that send up culms. Their roots are shallow but spreading. Although most members of the group are from the tropics and subtropics, bamboo is found in China almost as far north as the Siberian border, and Japanese bamboo thrives in areas noted for their hard winters. In fact, the Japanese and Chinese prize several species for their winter foliage.

Because bamboo is rhizomatous it is easily grown well north of its normal hardiness zones by planting in a protected microclimate and mulching heavily. Although a hard freeze will kill the culms, the plant won't die if the rhizomes are protected by a thick layer of mulch. When the weather warms up new culms will shoot up. If you live where the temperature doesn't drop below minus 20 degrees, a wide selection of bamboos is available to you.

Watching bamboo grow is a remarkable experience. Most varieties, particularly those from temperate climates, have a definite one - or two - month growing season during which they put out most or all of their new culms. Once the shoots break through the ground they grow very rapidly - as much as a foot a day on some of the tropical giants. By season's end the culms will have reached their full height. Leaves are borne on branches that spring from buds at the nodes (the jointlike rings). Although a culm won't grow any taller or thicker, its foliage will get bushier as long as the culm lives, usually several years.

Regardless of what you might have heard, bamboo will not invade your pipes or crack your concrete. Some varieties, such as Japanese arrow bamboo (Pseudosasa Japonica) and many Phyllostachys species, will take over your yard, then go visit your neighbors if you let them. but these invasive tendencies can be controlled.

Unlike some other invasive plants, notably willows. bamboo will not clog pipes. Bamboo is shallow-rooted, seldom reaching down more than 2 feet for even the largest varieties. Its invasiveness is solely in its spreading.

While it is true that bamboo won't crack concrete, it will push up through asphalt paving or between bricks or flagstones that aren't laid in cement. It also goes through black polyethylene film like it isn't even there. If your bamboo is bordered by a susceptible paving, you may want to put in a barrier to control its spread.

RUNNERS AND CLUMPERS

Broadly, ornamental bamboos divide into runners" and "clumpers." Both expand by sending out rhizomes, but the runners' rhizomes reach out much farther before they send up shoots. Even in their second or third year, runners will poke up shoots 4 or 5 feet from the main clump; at maturity some of the timber giants will send up shoots 20 feet from the nearest stalk.

Clumpers put out shoots much closer to the main bunch and spread more slowly. My five-year-old clump of punting pole bamboo has expanded only about 3 feet in every direction since I planted it. Each year new shoots appear around the periphery of the clump but never more than a foot from the nearest culm.

Clumpers are self-limited and no more of a problem than any other tree or shrub of the same size. However, most of the clumping bamboos are from warm climates; the hardy bamboos, such as the genus Phyllostachys, are often runners.

The easiest way to slow the growth of bamboo is to restrict its food and water. If you confine it in a pot or planter or behind a root barrier, bamboo will remain small.

Bamboo's spreading is easy to control because of another botanical peculiarity. There are a limited number of buds on each rhizome, each capable of producing just one culm. Each bamboo shoot is built like a jack-in-the-box; all its nodes are already present in compressed form when the shoot first pokes its head up. If you slice through a newly emerged shoot, you can count the number of segments the culm would have had. The practical effect is that, if you cut off a bamboo shoot, it doesn't resprout.

I find the best weapon against bamboo springing up in my lawn is a lawn mower. Just mow down the shoots with the rest of the grass; after a couple of mowings, the shoots give up.

If you want, you can build a barrier around the planting to stop the plant from running. With timber giants a trench about 3 feet deep is sufficient; either leave it exposed, fill it with leaves (and search through it every spring for new rhizomes) or install a barrier and backfill the trench. One of the best barriers is the aluminum flashing sold in home centers for roofing (just don't leave gaps or unsealed cracks). It is especially effective if angled away from the plant; rhizomes that reach the barrier are directed up toward the surface.