Wasabi

A Native Japanese Species

A plant native to Japan, wasabi (wasabia japonica) can be found in the shallow waters of clear streams deep in cool mountainous areas and takes from eighteen months to three years to grow. The rhizome, or lower stem, is the main part that is eaten; however, nothing is wasted as everything from the flowers and leaves to the tip of the white root can be used.

Japan’s wasabi, known as hon-wasabi, is clearly distinct from seiyō-wasabi (“Western wasabi” or horseradish). Wasabi has a refreshing, sweet aroma that is quite different from that of horseradish. When grated, wasabi becomes green, whereas horseradish turns white.

If you were to bite into the rhizome itself, you would find that wasabi is not actually spicy at all. Finely grating it is what creates the bite. Enzymes in the cellular tissues react chemically due to the action, releasing the pungency. The finer the wasabi is grated, the spicier it becomes, and the traditional way is to grate it in a circular motion on a grater made from shark’s skin. Samegawa shark skin graters can be found at sushi restaurants and soba noodle shops, but not normally in ordinary households because of the difficulty in obtaining wasabi rhizomes, which are considered to be a luxury food item.

(Left) A samegawa shark skin grater being used to grate wasabi into a paste; (right) horseradish. (© Pixta)

A Long History of Consumption

Records show that wasabi was already in use as a medicinal herb in the Asuka Period (593-710). In the early Edo period (1603–1868), it began being cultivated in what is now Shizuoka Prefecture. It was initially used as a condiment for soba noodles, but was something gifted to shoguns and not available to the general public.

(Clockwise from top left) Grated wasabi, wakegi scallions, grated daikon radish, wasabi, soba tsuyu dipping sauce, zarusoba cold buckwheat noodles. (© Pixta)

In the early 1800s, the invention of nigirizushi, the now internationally famous form of sushi that has grated wasabi between the sushi rice and the neta topping, led to a surge in popularity for the dish in Edo (now Tokyo).

Nigirizushi, which has wasabi between the neta topping and sushi rice. (© Pixta)

While wasabi has long been an essential ingredient for people of high status, nowadays it is in every household, used to accompany a variety of dishes like sashimi, different kinds of sushi, soba noodles, ochazuke green tea over rice, or steak. It is even used in Western cuisine, such as pasta, cheese, dipping sauces, and desserts.

Unagi no dashi-chazuke (Eeel and soup stock over rice). (© Pixta)

Hydroponics and Soil Farming

Wasabi is cultivated in two ways: hydroponics and soil farming. The typical kind of wasabi cultivated in Japan, using the plentiful clear stream water in mountain forests, is sawa-wasabi (wasabia japonica Matsumura, or water wasabi). Hata-wasabi (field wasabi) is cultivated in cool, wooded regions.

Wasabi is difficult to cultivate as it is sensitive to high and low temperatures. The flowing water needs to be around 12 to 13 degrees and even in midsummer it is best if the temperature stays below 16 degrees.

The traditional tatamiishi cultivation method is mainly used in the Mount Amagi area of Shizuoka Prefecture, with the wasabi grown on terraced slopes. It has been used for 400 years, and in 2018 it was recognized as a Globally Important Agricultural Heritage System by the Food and Agriculture Organization of the United Nations. In this method, cultivators dig a foundation and cover it with layers of large stones, pebbles, and finally sandy soil. The wasabi is planted on top and spring water allowed to flow along the sandy surface layer. While a lot of water is needed, the good ventilation means the wasabi grows quickly.

The heichi flat-terrain cultivation method is used in Nagano Prefecture, which along with Shizuoka, is a major wasabi-producing area. It involves digging one to two meters down into the flat ground alongside rivers to create ridges into which the wasabi is planted. Underground water from beneath the riverbed is used.

The wasabi fields at Izu, Shizuoka, recognized as a World Agricultural Heritage Site. (© Pixta)

Hata-wasabi, grown in the mountain valleys around Iwate, Shizuoka, and other prefectures, needs cool summers, warm winters, and good drainage. It is used mainly as an ingredient in processed products and neri-wasabi, a paste made from dried wasabi powder.

Wasabi Crossing the Seas

Although the majority of Japanese wasabi is produced in Shizuoka and Nagano, domestic production is falling year on year. Hata-wasabi is the main type produced and, as it is also grown overseas, it is imported in large quantities from countries including Taiwan, China, and Indonesia. Some countries also cultivate sawa-wasabi, the demand for which is on the rise due to consumers and overseas restaurants seeking real wasabi.

Processed Products

Every Japanese household has a tube of neri-wasabi paste. While it is not as sweet and does not have quite the same aroma as fresh wasabi, it is easily available. It is usually a combination of wasabi and horseradish, but there are also products that contain 100% hon-wasabi or that contain no coloring at all. In general, the greater the hon-wasabi content, the higher the price.

Wasabi paste from a tube. (© Pixta)

Wasabizuke is a pickle dish, comprising of chopped wasabi leaves, stems, and roots marinated in sake lees. It is a specialty in wasabi-producing areas. It can be enjoyed as a snack with alcoholic drinks or can be mixed with soy sauce to accompany kamaboko and other nerimono fish paste products.

Wasabizuke. (© Pixta)

There is an infinite number of possibilities for wasabi processed products. Wasabi-infused cheese, wasabi soft serve ice cream, and wasabi beer are among the many food items that are available.

Wasabi soft serve ice cream. (© Pixta)

(Banner photo: Wasabi, wasabi leaves, and a samegawa shark skin grater. © Pixta.)