"Nagaba-yabumao" (Boehmeria sieboldiana) belongs to Urticaceae (the Nettle family). It is a perennial herb that is distributed from Chubu region of Honshu, west to Shikoku and Kyushu in Japan. This herb grows on the edge of forests in the mountains and can reach 1 to 2 m in height. The stem has four ridges, and the ovate-oblong leaves are opposite. The leaf surface is shiny and has regular serrations. The spikes of about 20 cm are borne on the axils and small female flowers bloom from July to August. It is monoecious.