While common knotweed (Polygonum aviculare) grows as a low mat, its close relative, silversheath knotweed (Polygonum argyrocoleon) is an erect plant. Otherwise the two knotweed species are very similar. As mentioned in my previous post on common knotweed, both plants share a similar ecology, are annuals, are alien invaders over much of the United States and are considered noxious weeds.
Silversheath knotweed grows from 8 inches to 2 feet tall and has ascending, many-branched stems. The lanceolate leaves are smooth and their short stipules (stalks) are united at the base in a silvery membrane (ocrea). As the leaves grow the ocrea tears giving a raggedy appearance. The pinkish flowers are very small and occur in clusters of 2 to 5 along the stem at the top of the plant. As with other members of the buckwheat family the flower has five petals. These petals are fused into a tube.
Both common and silversheath knotweeds are edible if cooked as a potherb. Personally I prefer not to bother attempting to eat plants that because of their small leaves and wiry stems will probably be a stringy, unappetizing blob. I suppose if I were hungry enough. . .
Common and silversheath knotweed plants are used by herbalists as a diuretic and as an astringent, among other uses. Silversheath knotweed is sometimes called hindering knotweed because it was believed that if eaten by children the plant would hinder their growth. Probably not. . .
Persian knotweed is another common name for P. argyrocoleon because this species probably originated in Central Asia.
As with the common knotweed pictured in my last post, these silversheath knotweeds were growing in one of our fields (Modoc County CA).