Wasabi is a foundational ingredient in Japanese cuisine and has been grown in the country since the eighth century.
Wasabi, or Wasabia japonica, is a semi-aquatic perennial herb that is part of the Brassicaceae family, which also includes horseradish. Daruma and Mazuma are the two main cultivars produced in Japan and Taiwan as well as Tasmania here in Australia.
The plant is a high-value crop, and as such, production levels are declining due to difficulties relating to environmental factors as well as costs.
Growth and harvest
The plant was originally found in streams in Japan and is still grown in water today in addition to soil. Wasabi produced in water is said to be of superior quality to its soil counterpart, which is reflected in the price.
Wasabi does not tolerate direct sunlight and requires temperatures that remain under 25 degrees Celsius. For soil, wasabi should be planted in raised, shaded beds irrigated with high-quality water that can drain properly. If pollution is present in the water, wasabi will not survive. In Tasmania, daruma is grown in soil and mazuma is grown in water.
It takes between 22 to 24 months for wasabi to reach maturation, with the herb produced in two-year cycles. The stems are harvested by hand and should be trimmed and cleaned under potable water.
The leaves, petioles and stems are edible and can be harvested along with the stems. Sometimes, the stem is picked with the leaves still attached, which indicates freshness. Wasabi can be harvested at any time of the year if it has reached peak maturation.
Flavour profile and appearance
Wasabi plants have long stems that produce small white flowers. The knobbly stems are bright green in colour and can grow up to 10cm long and 3cm in diameter. Green leaves cover the stems and can reach up to 150mm in diameter.
The pungent flavour of wasabi can be likened to hot mustard or horseradish. It often generates a sensation in the nose rather than on the palate. It has a clean, white heat that results in a burning sensation when consumed.
There are several ways wasabi can be used. Most commonly, the stem is freshly ground using a square metal grater called an oroshigane. Wasabi is dabbed sparingly on sushi or sashimi by chefs or given to guests to use according to their own tastes. The herb’s stems and leaves can be made into a dried powder that’s used as a seasoning or to add flavour to chips, peas, cheese or rice crackers