Most wasabi served outside Japan is actually dyed horseradish.

True wasabi comes from Eutrema japonicum, a member of the mustard family. The familiar fresh condiment is made by finely grating its enlarged stem, commonly described as a rhizome. Horseradish comes from a different plant, Armoracia rusticana, and its pungent root is a common substitute.

The substitution works because the plants are botanical relatives with related pungent chemistry. Grating or crushing plant tissue brings components together that generate sharp-smelling compounds, including isothiocyanates. The resulting sensation is not identical to chili heat, which is associated with capsaicin and often lingers differently in the mouth.

Fresh wasabi is demanding to produce and comparatively costly. Prepared horseradish-based powders and pastes offer a more convenient alternative for food service. Some include genuine wasabi as one ingredient, so the useful distinction is not always a simple choice between entirely authentic and entirely fake.

Britannica identifies horseradish as a common substitute for true wasabi in Japanese cuisine. That supports the central explanation without requiring an unsupported global statistic. A restaurant's location alone cannot prove what is in its paste, because both genuine wasabi and substitutes can be served in different countries.

Traditional images of wasabi cultivation show cool, shaded beds with flowing water. Those conditions help explain its reputation as a specialist crop, but they should not become a claim that every plant must grow in a stream. Cultivation methods vary, and soil-grown wasabi also exists.

Grating fresh tissue creates the desired flavor but also starts a changing chemical mixture. The aroma and pungency do not remain fixed indefinitely. Serving freshly grated wasabi promptly is therefore part of the experience, although a universal countdown such as exactly fifteen minutes overstates how predictable the change is.

The bright green mound beside sushi is usually a prepared product whose ingredients cannot be identified confidently by color alone. A blend may be colored green, while genuine plant material also has natural color. Packaging, ingredient lists and an informed explanation from the restaurant are more useful than a visual authenticity test.

For packaged products, read the ingredients instead of relying only on the large word wasabi on the front. The list may identify horseradish, mustard, starch, coloring and some amount of wasabi. A product can be honestly labeled as a blend even if its flavor is mainly supplied by horseradish.

At a restaurant, ask whether the condiment is freshly grated wasabi, a commercial blend or a mixture containing some genuine wasabi. That question is more precise than asking whether it is real. Ingredient information also matters for people avoiding mustard or other components, and staff should check rather than guess about allergens.

A green mound is a presentation, not a botanical identification. A product may be genuine wasabi, a blend containing some wasabi, or a horseradish-based substitute. These are different ingredient descriptions. A worldwide proportion cannot be inferred from a few restaurants, familiar packaging or the fact that substitutes are widely discussed.