わが国の本州、日本海側から中国地方、紀伊半島それに四国・九州、朝鮮半島や中国東北部に分布しています。深い山地に生え、赤褐色の枝が蔓状に数メートル伸びます。葉は卵形から楕円形で浅い鋸歯があり、互生します。7月から8月ごろ、円錐花序をだして白色の5弁花を咲かせます。果実は翼果で、3個の翼があります。中国語では「雷公藤(lei gong teng)」と呼ばれます。
The "Kuro-zuru" (Tripterygium regelii) belongs to Celastraceae (the Bittersweet family). It is a small deciduous tree that is distributed to the Japan Sea side and Chugoku, the Kii peninsula of Honshu, Shikoku and Kyushu, as well as the Korean Peninsula and northeastern China. This tree grows in deep mountains and the reddish brown branches grow on long trailing vines. The leaves are ovate to elliptic and alternate with low toothed edges. The panicles are borne and bloom white five-petaled flowers from July to August. The fruits are samaras with three wings. It is called "雷公藤" (lei gong teng) in Chinese.