The great willowherb (Epilobium hirsutum) belongs to Onagraceae (the Evening primrose family). It is a perennial herb that is native to North Africa, most of Europe, and parts of Asia. It is rarely distributed northward from Chubu region of Honshu of Japan. This herb grows in wet or damp habitats without dense tree-cover up to 2500 m above sea-level, and can reach up to 2 m in height. The stems are robust, covered with profusely soft spreading hairs. The leaves are oblong to oblong-lanceolate, with sharply fine toothed edges. The flowers bloom from June to August. They have four notched petals, purple-pink and usually 10-16 mm long. The stigma is white and has four lobes.