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the name of more than 30, mainly Middle Asian, species of perennial plants of the genus Polygonum. There are about 15 species of knotweed in the USSR. The flowers have a corollaceous perianth, usually with eight stamens and a three-parted style; they are gathered into a loose panicle.
The best-known species is P. coriarium, which is found in Middle Asia in mountain zones at elevations of 1,700 to 2,800 m above sea level. The plant, which often forms an extensive dense cover, is usually 1 to 2.5 m tall and has a strongly developed root system. It is a valuable tanning plant; its roots have a tannin content of 15–25 percent. Several other closely related species, including P. songoricum and P. hissaricum, also yield tanning agents. The species P. alpinum is found in Middle Asia, the European USSR, the Caucasus, Siberia, and the Far East; it grows on plains, in mountain meadows, in steppes, along the edges of forests, and on rocky slopes. Its roots contain tannins. All knot-weeds yield significant amounts of nectar.
REFERENCESTaran dubil’nyi (Polygonum coriarium Grig). Tashkent, 1959.
Voprosy izucheniia i ispol’zovaniia dubil’nykh rastenii v SSSR. Moscow-Leningrad, 1963.
M. E. KIRPICHNIKOV