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Besieged by Bamboo? How to Counterattack

* Second of Two Parts

November 04, 2000|U.C. MASTER GARDENERS

Question: How can I control invasive bamboo?

W.L., La Habra

Answer: To control bamboo effectively, it's important to understand how it grows. Like Bermuda grass, bamboo grows from radiating rhizomes, which are long roots that radiate out horizontally from the parent plant.

They usually grow just below the soil surface and are rarely found more than 3 1/2 feet deep. The rhizomes produce stocks, or culms that sprout in the spring and early summer.

The secret to happily co-existing with your bamboo is to limit the spread of rhizomes by placing barriers around plantings. A small patch may be restricted to a bottomless oil drum extending at least 3 feet into the ground. Otherwise, the best way to control running bamboo is with a root barrier.

All root barriers begin with a trench. The trench should be dug around the area where you want bamboo to grow. It should be 3 to 3 1/2 feet deep. Since digging a 3-foot trench by hand is not a pleasant prospect, trenching machines such as the Ditch Witch can be rented from equipment companies.

Once a trench has been dug, there are two types of barrier that may be placed in the trench. Three inches of concrete stops the spread of rhizomes, or you can try a plastic root barrier found at farm supply stores and larger nurseries. They are made of black polyethylene, which is resistant to deterioration when exposed to ultra-violet light and durable under conditions of extreme pH variations.

You'll find this root barrier sold in rolls that are about 3 feet wide and 40 to 80 millimeters thick. They also generally come with fastener systems, which seal the seams where root barrier sections are joined. These root barriers are placed in trenches with the bottom folded inward toward the area where bamboo will be grown.

Whether you use concrete or polyethylene, the lip of the barrier should be allowed to extend 2 or 3 inches above the surface of the soil. This will make it easier to detect renegade rhizomes trying to slip over the top of the barrier. Even with a barrier in place, some rhizomes will escape.

Water may also be used to limit the spread of running bamboo. In our dry climate, if you use drip irrigation to water only the center of a bamboo clump and the surrounding area is kept dry, migration will be greatly discouraged.

Water may also be used as a natural barrier. Bamboo does not like growing in water and will not grow beyond the edge of a pond or stream, provided it is deep enough.

If you already have bamboo that has escaped its bed, dig it up. Or you can sever the rhizomes where they leave the bed and continue to knock down new shoots as they appear for the next few seasons.

Once the rhizomes are severed from the main plant, they will eventually die if new shoots are not permitted to grow.

New shoots may be knocked down mechanically as by mowing or chemically with a contact foliage spray designed to kill leaves.

*

For additional information on growing bamboo, contact the American Bamboo Society on the web at http://www.bamboo.org/abs.

-- Written by University of California master gardener Harold Pope of Irvine.

For answers to your garden questions contact the University of California Cooperative Extension Master Gardeners at their hotline at (714) 708-1646 or by e-mail at ucmastergardeners @yahoo.com.

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