Polygonum cuspidatum, commonly known as Bamboo, Japanese Bamboo, Japanese Knotweed, Mexican Bamboo and Rice Cane, is native to Japan and was introduced into the United States as an ornamental. Widely planted in the Northeast, it escaped from cultivation and became an obnoxious weed. Regardless of this fact, it can still be found in some nurseries.

Japanese bamboo grows 4 to 8 feet tall with stout, bushy, somewhat woody stalks. It spreads rapidly by stout underground rhizomes and offshoots or "suckers." The succulent tops are killed by frost each fall, and new shoots arise each spring from the rhizomes. The plant is often found in waste places and old neglected garden areas. It usually grows in dense thickets due to its suckering habit.

Control:

Japanese Bamboo is particularly difficult to kill because of the rhizomes it sends down deep into the soil. Pulling or digging out can control it, but because of the depth of the rhizomes, results are not too satisfactory. Soil sterilants seldom penetrate deep enough to kill all of the rhizomes, and new growth reappears. Several weed killers kill the tops of the plant but leave the roots virtually undamaged. Regrowth from the roots is rapid. Repeated cutting or killing of the top growth tends to weaken the plant but does not kill the roots.

Chemical Control:

Dicamba (one trade name is Banvel-D and is usually sold in combination with 2,4D) or glyphosate (one trade name is Roundup) will control Japanese Bamboo. Apply as a drenching spray at the peak of flowering, which occurs in late August and early September. The solution, diluted according to instructions of the manufacturer, should be sprayed on the foliage so that it begins to drip from the leaves. Be sure to cover both upper and lower surfaces of the leaves. If regrowth occurs, allow the plants to grow through the next summer and spray again in late August or early September.

Caution: Weed-killing chemicals are non-selective and will kill many kinds of broad-leaved plants. Take precautions that they do not come in contact through spray or drift with desirable plants in the vicinity. Weed killers also enter the ground and may kill or severely injure woody shrubs and trees whose roots are in the treated area or in the drainage pattern of the soil.

Adapted from the UMASS Cooperative Extension, 2001