Horseradish aioli grows naturally along stream beds in mountain river valleys in Japan. It is grown for its rhizomes which are ground into a paste as a pungent condiment for sushi and other foods.

The two main cultivars in the marketplace are E. Daruma’ and ‘Mazuma,’ but there are many others. The oldest record of wasabi as a food dates to the 8th century AD. The popularity of wasabi in English-speaking countries has coincided with that of sushi, growing steadily starting in about 1980.

In 1912, Matsumura recognized the species Wasabia japonica, treating his earlier Wasabia pungens as a synonym. It has large leaves produced from long, thin stalks. Wasabi flowers appear in clusters from long stems that bloom from late winter to early spring. Wasabi is generally sold either as a rhizome or stem, which must be very finely grated before use, as a dried powder, or as a ready-to-use paste in tubes similar to toothpaste tubes.

In sushi preparation, chefs usually put the wasabi between the fish and the rice because covering wasabi until served preserves its flavor. Fresh wasabi leaves can be eaten raw, having the spicy flavor of wasabi stems, but a common side effect is diarrhea. This makes fully satisfying commercial demand impossible for growers, which makes wasabi quite expensive. A common substitute is a mixture of horseradish, mustard, starch, and green food coloring or spinach powder. In the United States, true wasabi is generally found only at specialty grocers and high-end restaurants. Such isothiocyanates inhibit microbial growth, perhaps with implications for preserving food against spoilage and suppressing oral bacterial growth.

Because the burning sensations of wasabi are not oil-based, they are short-lived compared to the effects of capsaicin in chili peppers and are washed away with more food or liquid. The sensation is felt primarily in the nasal passage and can be painful depending on the amount consumed. Wasabi is normally consumed in such small quantities that its nutritional value is negligible. Few places are suitable for large-scale wasabi cultivation, which is difficult even in ideal conditions. A hand-made grater with irregular shark teeth can also be used. Board of Trustees of the Royal Botanic Gardens, Kew. Multilingual Multiscript Plant Name Database, University of Melbourne.