The "Aka-so" (Boehmeria tricuspis) belongs to Urticaceae (the Nettle family). It is a perennial herb that is native all over Japan, as well as the Korean Peninsula and China. It is a herb grows in wettish hills and fields, and can reach 50-100 cm in height. Its stem, petioles and female clusters are tinged red. The leaves are ovate, opposite and trilobate tips. The female clusters are borne on the upper stems and male ones are borne on the lower stems from July to September. Since the Jomon period (14000-300 BC), threads have been made from the fibrous material of the "jinpi", or bast between the xylem and the epidermis. In Chinese, it is called "八角麻" (ba jiao ma).