Most diners in the United States would be surprised to discover they’ve probably never tasted wasabi. That is the real stuff. Most of the wasabi served in sushi joints is made from reconstituted horseradish – with some green coloring. It turns out that it’s difficult to cultivate wasabi. It normally grows in pure, fresh flowing mountain streams.
I was recently in Japan and not only had the chance taste the real thing, but to also see it grow. This photo was taken in Yamanashi Prefecture at the base of a mountain spring. A beautiful site.
Freshly grated wasabi is more complex than powdered wasabi and is not as harsh. It is also very expensive.