two main cultivars in the marketplace are W. japonica var. Duruma and Mazuma, but there are many others.

Uses
Wasabi is generally sold either in the form of a root, which must be very finely grated before use, or as a ready-to-use paste, usually in tubes approximately the size and shape of travel toothpaste tubes. Once the paste is prepared it should remain covered until served to protect the flavor from evaporation. For this reason, sushi chefs usually put the wasabi between the fish and the rice.

Fresh leaves of wasabi can also be eaten and have some of the hot flavor of wasabi roots. They can be eaten as wasabi salad by pickling overnight with a salt and vinegar based dressing, or by quickly boiling them with a little soy sauce. Additionally, the leaves can be battered and deep-fried into chips.

Fortunately for those who mistakenly consume too much of this condiment, the burning sensations it can induce are short-lived compared to the effects of chili peppers, especially when water is used to dissipate the flavor. Wasabi paste bears a superficial resemblance to guacamole, a popular staple of Mexican-style cuisine, a similarity which can lead to an unpleasant surprise for those unfamiliar with Japanese food.

Wasabi is often served with sushi or sashimi, usually accompanied with soy sauce. The two are sometimes mixed to form a single dipping sauce known as Wasabi-joyu. Wasabi peas and peanuts are growing in popularity, most notably in the United States. These legumes are roasted or fried, then coated with a wasabi-like mixture (usually an imitation). These are then eaten as an eye-watering "in the hand" snack.

Wasabi Ice Cream is a recent but increasingly popular innovation.

Preparation
Wasabi is often grated with a metal oroshigane, but some prefer to use a more traditional tool made of dried sharkskin with fine skin on one side and coarse skin on the other. A hand-made grater with irregular teeth can also be used.

The Eating Experience

People with particularly sensitive sinuses should use caution when eating wasabi since those with pre-existing conditions might experience sinus inflammation as a result of the irritation by the wasabi vapor.

Wasabi and imitations
A tube of wasabiAlmost all sushi bars in America, and some cheap ones in Japan, serve imitation (seiyō) wasabi (see Etymology section, below) because authentic wasabi is relatively more expensive. Although harder to find, real wasabi powder (from Wasabia japonica plant) is a convenient way to experience true wasabi's remarkable flavor, but most commercially available "wasabi" powders contain no true wasabi at all. Most utilize a powdered imitation made from horseradish, mustard seed, and green food coloring (sometimes Spirulina). Whether real or imitation the powder is mixed with an equal amount of water to make a paste.

To distinguish between the true variety of wasabi and the imitation product, real wasabi is known in Japan as hon-wasabi ( 本山葵), meaning original, or true wasabi.

Chemistry
The chemicals in wasabi that provide its unique flavor are the isothiocyanates, including:

6-methylthiohexyl isothiocyanate,
7-methylthioheptyl isothiocyanate and
8-methylthiooctyl isothiocyanate.

Research has shown that isothiocyanates have beneficial effects such as inhibiting microbe growth. This may partially explain why wasabi is traditionally served with seafood, which spoils quickly. However, if the quality of one's seafood is questionable, one should not eat it raw, with or without wasabi. It is not a treatment for food poisoning.

Cultivation
Few places are suitable for large-scale wasabi cultivation, and cultivation is difficult even in ideal conditions. In Japan, wasabi is cultivated mainly in these regions:

• Izu peninsula
• Nagano prefecture
• Shimane prefecture
• Yamanashi prefecture
• Iwate prefecture

There are also numerous artificially cultivated facilities as far north as Hokkaidō and as far south as Kyūshū. The demand for real wasabi is very high. Japan has to import a large amount of it from:

• Mainland China and
• Ali Mountain of Taiwan
• New Zealand.

In North America, a handful of companies and small farmers are successfully pursuing the trend by cultivating Wasabia japonica. While only the pacific northwest and parts of the blue ridge mountains provide the right balance of climate and water for natural cultivation of sawa (water grown) wasabi, the use of hydroponics and greenhouses has extended the range.

• British Columbia, Canada
• Oregon, North Carolina, United States

While the finest sawa wasabi is grown in pure, constantly flowing water, without pesticides or fertilizers, some growers push growth with fertilizer such as chicken manure, which can be a source of downstream pollution if not properly managed.

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