わが国の各地をはじめ、朝鮮半島に分布しています。日当たりの良い草地や疎林に生え、高さは20〜25センチになります。暗紫色を帯びた茎が直立し、狭い披針形の葉が対生します。9月から11月ごろ、茎の先に円錐花序をだし、白色の花を咲かせます。花弁には紫色の縞模様が入ります。和名は、千回振り出してもまだ苦いということから。全草を乾燥したものは当薬(とうやく)と呼ばれ、健胃・整腸薬として利用されます。中国語では「日本當藥(ri ben dang yao)」と呼ばれます。
The "Senburi" (Swertia japonica) belongs to Gentianaceae (the Gentian family). It is a biennial herb that is native all over Japan, as well as the Korean Peninsula. This herb grows in sunny grasslands and thin forests, and it can reach 20-25 cm in height. The stems are dark purple tinged and upright. The leaves are narrow lanceolate and arranged in opposite. The panicles are borne on the top of stems, and the white flowers bloom from September to November. The petals are purple-streaked. The Japanese name comes from the idea that even after shaking it a thousand times, it still tastes bitter. The dried plants are called "Toyaku" and used as a treat stomach or intestinal remedy. It is called "日本當藥" (ri ben dang yao) in Chinese.