タデ科イタドリ属の多年草で、学名は Reynoutria japonica (syn. Fallopia japonica var. japonica、Polygonum cuspidatum)。英名は Japanese knotweed。
The Japanese knotweed (Reynoutria japonica) belongs to Polygonaceae (the Knotweed family). It is a perennial herb that is native to Japan, as well as Taiwan, the Korean Peninsula and China. This herb grows in hills and dales and can reach 50-150 cm in height. It spreads by long rootstocks in the grounds and bears midair young shoots in spring. They have a sour taste and edible. The compound racemes are borne on the terminal branches and bloom small white flowers from June to September. The rootstocks are used a herbal medicine for laxative and diuretic agent.