Wasabi is on the table at every sushi restaurant in the U.S. The only problem is it’s not wasabi.
What is wasabi?
The wasabi plant is a rhizome. Rhizomes, like bamboo, spread by roots and nodes. This should make propagation of the plant easy.
However, wasabi requires specific growing conditions. Low humidity is necessary for the wasabi plant to flourish. So is precise fertilization. And, when grown on a large scale, wasabi plants are susceptible to disease. Because of this, demand for wasabi far outstrips the miniscule supply that is grown every year. In fact, Japan has to import wasabi to keep up.
Because of the limited supply and high cost of real wasabi, fake wasabi is almost always served in North American sushi restaurants.
That green paste on your plate, often called western wasabi in Japan, is a mixture of grated horseradish, mustard, and food coloring.
Horseradish is a decent, if overwhelming, substitute because the wasabi plant is related to the horseradish plant. But, horseradish has an overpowering spiciness that isn’t known in real wasabi.
There are a few secrets to determining if you’ve been served real or fake wasabi. First, look at the color. Real wasabi has a pale green/yellow color, not the neon green color of the fake stuff. Second, real wasabi is freshly grated so it will have a slightly gritty texture. Fake wasabi usually has a smooth texture.
Finally, check the heat and aroma. Real wasabi doesn’t have the powerful spiciness of horseradish. Instead, real wasabi is more about the aroma. The spiciness level of real wasabi won’t overwhelm the food like the fake stuff.
Where to get real wasabi
It is very rare to find real wasabi in a North American sushi restaurant. Ask your server if their wasabi is freshly grated and then inspect it for color, texture, and flavor when it is served to you.
There are stores that sell wasabi paste, made from real wasabi rhizomes. Paste is an adequate substitute when cooking at home.
Fresh wasabi rhizomes, grated in your kitchen are best. It is rare to find a store selling fresh wasabi rhizomes, but there are online stores that sell the good stuff. Be aware that fresh wasabi rhizomes are expensive and will last for about a month in your fridge.