Have you ever eaten wasabi?

If you answered “yes” to that question, you are likely mistaken. Most sushi eaters—even in Japan—are actually being served a mixture of ground horseradish and green food coloring splashed with a hint of Chinese mustard. Worldwide, experts believe that this imposter combination masquerades as wasabi about 99% of the time.

The reason boils down to supply and demand. Authentic wasabi, known as Wasabia japonica, is the most expensive crop to grow in the world. The temperamental semiaquatic herb, native to the mountain streams of central Japan, is notoriously difficult to cultivate. Once planted, it takes several years to harvest; even then, it doesn’t germinate unless conditions are perfect. Grated wasabi root loses its flavor within 15 minutes.

The Japanese have grown wasabi for more than four centuries. 75-year old Shigeo Iida, the eighth-generation owner of his family’s wasabi farm in Japan, takes pride in his tradition, which is profiled in Edwin Lee’s short documentary "Wasabia Japonica," co-produced by Japan Curator. “Real wasabi, like the ones we grow, has a unique, fragrant taste that first hits the nose,” Iida says in the film.