wasabi Eutrema wasabi (formerly Wasabia japonica), a perennial herb which is not related to horseradish but resembles it in flavour, and is often referred to as ‘Japanese horseradish’. It is found elsewhere in E. Siberia, but belongs essentially to Japan, where it is used extensively, providing one of the most important flavourings in Japanese cookery.
The plants grow wild in or on the banks of mountain streams and are cultivated in flooded mountain terraces. This cultivation requires great care, since the water temperature has to remain a constant 11–14 °C (51–7 °F) throughout the year. Nagano, Shizuoka, and Shimane are the main growing districts in Japan. The plants take several years to reach maturity.