わが国の本州から四国・九州、それに朝鮮半島や中国に分布しています。山地の沢沿いの明るい林内に生え、高さは20〜30センチになります。葉は卵円形で縁には鈍鋸歯があり、長さ2〜3センチの葉柄がつきます。4月から5月ごろ、茎頂に穂状花序をだし、きれいな紫色の花を咲かせます。花後、走出枝を伸ばして広がります。和名は、花のかたちを羅生門で切り落とされた鬼の腕に喩えたもの。中国語では「蕁麻葉龍頭草(qian ma ye long tou cao)」と呼ばれます。
The Meehan's mint (Meehania urticifolia) belongs to Lamiaceae (the Mint family). It is a perennial herb that is native from Honshu to Shikoku and Kyushu in Japan, as well as the Korean peninsula and China. This herb grows in open forests along mountain streams, and it can reach 20-30 cm in height. The leaves are ovate-round with obtuse serrated edges and 2-3 cm long petioles. The spikes are borne atop of stems and the pretty purple flowers bloom from April to May. After flowering, it spreads by basal stolons. The Japanese name is a metaphor for the shape of a flower to the cut off demon's arm at Rashomon (the gate built at the southern end of the Suzaku Avenue in the ancient Kyoto). It is called "蕁麻葉龍頭草" (qian ma ye long tou cao) in Chinese.