Wasabi or Japanese horseradish is a plant of the family Brassicaceae, which also includes horseradish and mustard in other genera. The plant is native to Japan and the Russian Far East including Sakhalin, as well as the Korean Peninsula. It grows naturally along stream beds in mountain river valleys in Japan.

Brassicaceae or Cruciferae is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The leaves are simple, lack stipules, and appear alternately on stems or in rosettes. The inflorescences are terminal and lack bracts. The flowers have four free sepals, four free alternating petals, two shorter free stamens and four longer free stamens. The fruit has seeds in rows, divided by a thin wall.