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).http://www.ecy.wa.gov/programs/wq/plants/weeds/aqua015.html
Common names: Japanese knotweed, fleeceflower, Mexican bamboo, huzhang
Japanese knotweed (Polygonum cuspidatum or syn. Fallopia japonica) is a perennial species with spreading rhizomes and numerous reddish-brown, freely branched stems. The plant can reach four to eight feet in height and is often shrubby. The petioled leaves are four to six inches long and generally ovate with an abrupt point. The whitish flowers are borne in open, drooping panicles. The plant is dioecious, so male and female versions of the inconspicuous flowers are produced on separate plants. The approximately 1/8 inch long fruits are brown, shiny, triangular achenes, (Hitchcock and Cronquist 1964; Hickman 1993).
Japanese knotweed is a very aggressive species (Hitchcock and Cronquist 1964) that is capable of crowding out all other vegetation (Ahrens 1975); Hickman (1993) lists the species as a noxious weed. In addition, the plant can create a fire hazard in the dormant season (Ahrens 1975). Japanese knotweed is an escaped ornamental that is becoming increasingly common along stream corridors and rights-of-way in Washington. The species forms dense stands that crowd out all other vegetation, degrading native plant and animal habitat. This perennial plant is difficult to control because it has extremely vigorous rhizomes that form a deep, dense mat. In addition, the plant can resprout from fragments; along streams, plant parts may fall into the water to create new infestations downstream.