Bamboo shows off, and behaves

Bamboos are among the most versatile plants in our gardens. They are at home in the serene green of Japanese gardens as well as in colorful tropical gardens that call to mind Mexico, Jamaica, and Bali.

Bamboos come in so many shapes and sizes that they can screen out a two-story town house, form the walls of an outdoor room, or sit demurely in a small pot on the windowsill.

Some people are afraid of bamboo's reputation for growing out of control. Ralph Evans of Botanical Partners, a bamboo nursery in Vista, Calif., (www.botanicalpartners.com) works hard to counter gardeners' fears of bamboo.

Mr. Evans and other bamboo aficionados know that running bamboo can be contained quite easily by surrounding the roots with a sturdy root barrier.

Clumping bamboos, on the other hand, mind their manners and stay pretty much in the spot where you plant them. Before you buy a bamboo, be sure you know whether it is a clumper or a runner.

What a relief to realize that if you love the look of bamboo, you can plant it without fear that you'll wake up one morning to discover it has taken over your entire yard!

There are so many options that you are sure to find at least one bamboo that fits your needs, regardless of your garden's size or location.

You'll want to start your hunt by researching the light requirements of bamboos that appeal to you. Different species tolerate varying amounts of sun and shade.

Success may also depend on the intensity of the sun in your garden. What does well in full sun in overcast Seattle, for example, would fry in San Diego's bright light.

Bamboo isn't at all difficult to grow. It likes well-drained, slightly acidic to neutral soil that has been amended heavily with organic matter.

Start fertilizing when you see new growth – as early as February in some parts of the country. Use a high-nitrogen fertilizer that's made for grass; it can be slow-release or fast-acting.

Apply it at the rate recommended on the label for the same square footage of grass. Naturally, you'll want to avoid any fertilizer that contains a herbicide, since it will harm your bamboo.

Water deeply and regularly the first few weeks after planting. After that, established bamboo needs no more water than an equivalent area of lawn.

Mulch new plantings with straw, hay, lawn clippings, etc. Later, allow six inches of bamboo leaves to amass beneath the culms (stalks) and over the roots. This keeps the soil moist, insulates roots, discourages weeds, and recycles critical nutrients back to the plant.

If you'd like to increase your supply of bamboo, propagation is easiest in spring when new growth starts. Use a knife or sharp shovel to separate a section with stem and roots from the rest of the plant, and replant it where you'd like it to grow.

Many bamboos do well in pots, both indoors and out. Use a standard potting mix, high in composted humus. Water regularly. If you live in a cold-weather area, bring pots indoors to a spot with bright light (or put them in a greenhouse) in winter. Indoor plants can suffer in dry heat, so try to increase humidity levels (or occasionally place the plant, pot and all, in the tub and turn on the shower briefly).

To winter-proof bamboo: Cut it back before cold weather arrives to prevent new growth that can be harmed by winter temperatures. Spread mulch six to 12 inches deep around the plants. With some plants, culms may die back, but if mulched sufficiently, plants will resprout in spring.

Before you plant a running bamboo, decide how wide to allow it to grow. To keep it from taking over your property – and possibly your neighbor's – install a root barrier to keep the plant within bounds:

1. Dig a trench at least three feet deep around the perimeter of the planting hole. Angle the trench outward toward the top so that as rhizomes hit the barrier, they are deflected upward.

2. Line the hole with a three-inch-thick layer of concrete or with HDPE (high-density polyethylene) root barrier, 40 millimeters thick and 30 inches deep. (HDPE root barrier is sold by the roll at larger nurseries.)

3. Leave two or three inches of root barrier or concrete above ground level so you can see the roots that climb over the top of their enclosure. Cut them off when they appear.

4. From midsummer to late fall, plants put out tender new rhizomes. Starting the second year after planting, take a flat-edge spade and cut around the perimeter of the plant to separate new rhizomes from the plant. Remove unwanted rhizomes.

5. Each year before the plant starts its spring growth, thin out running bamboo. Remove the oldest culms before they reach the end of their natural life span, typically four to six years. Once new growth begins, watch for wayward roots that attempt to escape the root barrier.

How much cold weather can bamboos tolerate? Many gardeners are under the misconception that bamboos grow only in mild climates. Not true, says Susanne Lucas, horticulturist and president of the American Bamboo Society (www.americanbamboo.org).

Ms. Lucas grows more than 60 types of bamboo in her Plymouth, Mass., garden.

She plants hardy bamboos, many of which are native to high-elevation regions of China. They tolerate temperatures of minus 20 degrees F.

Lucas grows less-hardy bamboos in pots and moves them indoors or into a greenhouse for winter.

Bamboo expert Ted Meredith, author of a new reference, "Bamboo for Gardens" (Timber Press, $39.95), grows bamboo in the maritime climate of the Pacific Northwest.

In his region, freezing temperatures are common in the winter but hard freezes are not. However, Mr. Meredith makes the point that gardeners as far north as the Arctic Circle can grow bamboo.

Some type of bamboo will thrive in every state within the continental US, says Meredith. Recommendations for cold-hardy bamboos and bamboos that prefer mild climates are given in lists with this article.

According to Massachusetts resident Susanne Lucas of the American Bamboo Society, at least 150 types of bamboo are hardy enough for USDA Zone 6 gardens, where winter temperatures may fall to minus 10 degrees F. Some live in even colder climates. These are a few of her favorites:

• Umbrella bamboo (Fargesia murielae). The plant has a green culm (stalk) and pea-green leaves. The upper portions of the culms arch like an umbrella. It grows to 15 feet tall and is hardy to minus 20 degrees F.. It prefers morning sun or full shade. It's a clumper.

• Blue fountain bamboo (Fargesia nitida). Dark red-purple or brown-purple culms to 18 feet tall. Delicate green leaves. Hardy to minus 20 degrees F. Morning sun or full shade. Clumper.

• Yellow groove bamboo (Phyllostachys aureosulcata). Green culms with yellow grooves grow – sometimes in a zigzag shape – to 25 feet tall. Hardy to minus 10 degrees F. The most reliable tall bamboo in the Northeast. Runner.

• Phyllostachys vivax. Green culms to 35 feet or taller. Hardy to minus 5 degrees F. It's the hardiest of the timber bamboos. Shoots are excellent for eating. Runner.

• Black bamboo (Phyllostachys nigra 'Hale'). Culms turn black as they age. Reaches 20 feet tall. Hardy to minus 5 F. Grow in shade. Protect with extra mulch in winter. Runner.

• Pleioblastus viridistriatus. Striped leaves: grass-green with bright yellow. To three feet tall. Hardy to 10 degrees F, but not evergreen. Shade. Ground cover. Runner.

• Kumazasa (Sasa veitchii). Dark green leaves develop white margins in winter. Great in a wooded garden. Two to three feet tall. Hardy to zero F. Evergreen. Ground cover. Runner.

Where winters are mild, temperate and tropical bamboos thrive. Look for:

Alphonse Karr bamboo (Bambusa multiplex ). Bright-yellow culms (stalks) and random dark-green stripes. Grows to 26 feet tall. It's hardy to 12 degrees F., and is a clumper.

Golden goddess bamboo (Bambusa multiplex ). Branches start low and crisscross so you cannot see through them. Hedge to 8 feet. Hardy to 12 degrees F. Clumper.

Giant timber bamboo (Bambusa oldhamii). A tropical bamboo growing more than 40 feet tall with deep-green culms 4 inches across. Minimum temperature: 20 degrees F. Clumper.

Buddha's belly bamboo (Bambusa tuldoides 'Ventricosa'). Has zigzagging, bulging culms and branches. Grows to 40 feet high. Will be a dwarf in a pot. Minimum temperature: 15 degrees F. Clumper.

Marbled bamboo (Chimonobambusa marmorea). Shoots and leaves marbled with cream and purple. Mature culms turn red or dark purple. Grows to 4-1/2 feet tall. Minimum temperature: 15 degrees F. Runner.

Square bamboo (Chimonobambusa quadrangularis). Cross sections of stem are square with rounded corners. Outdoors, it forms an 18-foot hedge. Minimum temperature: 15 degrees F. Runner.

Indocalamus tessellatus Deep-green arrow-shaped leaves are long and broad. Culms to 5 feet tall. Shade. Hardy to minus 5 degrees F. Runner.

Mexican weeping bamboo (Otatea acuminata aztecorum). Tall weeping hedge to 15 feet. Suited to container culture indoors or out. Minimum temperature: 22 degrees F. Clumper.

Green onion bamboo (Pseudosasa japonica 'Tsutsumiana'). Variegated bamboo with swollen sections of culm, much like a green onion. Grows to 13 feet tall. Suited to container culture indoors or out. Minimum temperature: minus 5 degrees F. Part shade. Runner.

For more information, see "Bamboo for Gardens," by Ted Jordan Meredith, and "The Gardener's Guide to Growing Temperate Bamboos," by Michael Bell. Both are published by Timber Press.