Eutrema japonicum (wasabi)

Japanese name: ワサビ （山葵）
Scientific name: Eutrema japonicum

[Overview]
A perennial 20–40 cm tall, growing in wet ground beside clear mountain streams deep in the mountains and on slopes along valleys.
The whole plant has a distinctive pungency.
It has a thick, cylindrical rhizome with many nodes.
The stem is erect and bears several leaves, and there are also basal leaves at the base.
The leaves are simple, basal or alternate, glossy on the upper surface, and round with a heart-shaped base, 6–12 cm across.
The leaf margins have wavy teeth.
A short raceme emerges at the stem tip.
The flowers are white with 4 petals, and the petals are long obovate, about 6 mm long.
The fruit is a silique 1.5–1.7 cm long, constricted like a string of beads, and the seeds are long elliptical, about 3.5 mm long.

[Uses]
The enlarged rhizome is used as a spice, and it is cultivated in Shizuoka, Nagano and elsewhere.
The leaves, stems and flowers are also eaten.
The rhizome is known to have preservative and antibacterial effects.
It is also used medicinally.

[History]
It appears as "委佐俾三升" on a wooden tablet (mokkan) from the Asuka period, and is thought to have been used medicinally in the Nara period.
It is said to have come to be used as a condiment, as it is today, in the Muromachi period.
It is said that cultivation began in the early Edo period in the Utogi district of present-day Shizuoka City.
At first it was kept from being taken out of the district, but cultivation gradually expanded.

[Cultivation]
Propagate from seed or by division.
There are two cultivation methods: "Mizu-wasabi," grown in shallow places where clear water flows, and "Hata-wasabi," grown in a field.
It has weak heat tolerance and prefers a cool environment.
The suitable temperature for growth is about 15–16 °C for the water and 8–20 °C for the air; in summer give it partial shade out of direct sunlight, and in winter let it receive sun.
Growing it in a field is easier, but it can also be grown as "Mizu-wasabi" by using a planter that can hold water and changing the water frequently.
Pests and diseases include soft rot and cabbageworms.

View this page in Japanese (日本語)