The prized part of the wasabi plant is its thick knobbly stem, which is often but incorrectly called a rhizome or root, which can grow up to 10cm long and 1–3cm in diameter.
The stem is usually sold with some of its leaf stalks attached to help indicate freshness. It has long flowering stems with small white flowers. The stems, flowers, leaf stalks (petioles) and leaves of the wasabi plant are all consumed.
As wasabi is a cool climate plant, it is suited to regions with a maximum summer temperature of below 25°C. This confines its production to cool-temperate areas of Tasmania.
Wasabi can is ideally grown in a shaded position protected from severe frost .
It is important to have a well drained ,organically enriched soil (drainage is essential) and soil pH should be in the range 6.5–7.5.
Wasabi is a cool climate crop. It can tolerate air temperatures ranging from mild frosts to 25°C but it is sensitive to heat stress and waterlogging.This means it must be grown in cool, shaded conditions.
The ideal root temperature for production is 12–15°C, although the plant can tolerate mild frosts, root temperatures below this range will impede growth. Plants may show stress if the root temperature exceeds 15°C.
Soil-grown wasabi will require irrigation throughout the year, and the site must have an abundant supply of very high quality water. Even low levels of pollution in the water will affect the crop.