Monday, November 2, 2009

Japanese Knotweed

Japanese Knotweed, Polygonum cuspidatitm, is right up there with Oriental Bittersweet in its ability to take over the landscape. It seems to like moist ground as I most often find it bordering swamp and pond.

Yet in spite of its invasiveness, Japanese Knotweed shows many uses. From Wikipedia:

Japanese knotweed flowers are valued by some beekeepers as an important source of nectar for honeybees, at a time of year when little else is flowering. Japanese knotweed yields a monofloral honey, usually called bamboo honey by northeastern U.S. beekeepers, like a mild-flavored version of buckwheat honey (a related plant also in the Polygonaceae).

The young stems are edible as a spring vegetable, with a flavor similar to mild rhubarb. In some locations, semi-cultivating Japanese knotweed for food has been used as a means of controlling knotweed populations that invade sensitive wetland areas and drive out the native vegetation. Some caution should be exercised when consuming this plant because it contains oxalic acid, which may aggravate conditions such as rheumatism, arthritis, gout, kidney stones or hyperacidity.

Both Japanese knotweed and giant knotweed are important concentrated sources of resveratrol, replacing grape byproducts. Many large supplement sources of resveratrol now use Japanese knotweed and use its scientific name in the supplement labels. The plant is useful because of its year-round growth and robustness in different climates.

Japanese knotweed is a concentrated source of emodin, used as a nutritional supplement to regulate bowel motility. The roots of Japanese knotweed are used in traditional Chinese and Japanese herbal medicines as a natural laxative. The active principle responsible for the laxative effect is emodin, present in its natural form as a complex of its analogs. Emodin has a mild laxative effect in doses of 20 to 50 mg per day.

From Annual Report of The Pennsylvania State College:

The Japanese Knotweed, also known as the Giant Knotweed, is a newcomer into the weed society. In the first edition of Britton and Brown's "Illustrated Flora of the United States and Canada" this plant was reported as having escaped locally in the vicinity of Philadelphia, Pennsylvania, Schenectady, New York, and Atlantic Highlands, New Jersey; in the second edition of the same work, published in 1913, the plant is described as having escaped from cultivation locally throughout the entire range from Newfoundland to the parallel of the southern boundary of Virginia and from the Atlantic Ocean westward to the 102nd meridian. As the name implies, the plant was introduced from Japan.

At present the Japanese Knotweed is offered for sale in the catalogs of practically all the leading seed houses. In several places in the vicinity of the College, the plant has escaped its bounds to become a vile weed difficult of control; the heavy, woody, deepseated root stock makes this plant extremely pernicious once it leaves the desired bounds. For this reason intending purchasers are warned against the introduction of the plant into their garden. Similar complaint has been registered against the plant by Mr. John Ellis while acting in the capacity of gardener in the Brooklyn Botanic Garden.

Annual Report of The Pennsylvania State College. Harrisburg, 1919. 325. Web. Google Book Search. 1 Nov 2009.

"Japanese knotweed." Wikipedia, The Free Encyclopedia. 30 Oct 2009, 11:36 UTC. 2 Nov 2009 <>.

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