Introduction

Wasabi, also known as Japanese Horseradish, is a member of the Cruciferae (mustard) family and is a native of Japan. It occurs naturally alongside mountain streams. The rhizome is the most valuable part of the plant. This can be harvested and exported fresh or processed in New Zealand also for export. The less valuable leaves and petioles are ground up into the paste that is commonly seen in restaurants and supermarkets.

After planting, the crop is grown for 14–20 months until the rhizomes are a harvestable size. The current crop growing at the Crop Center in Invercargill has put on most of its growth in the cooler winter months. It does not like hot temperatures (+ 25° C) or direct sunlight. At harvest the whole plant is removed from the ground. The rhizomes can be separated and exported fresh to markets in Japan, where it can fetch high prices. The remaining stems and leaves are usually ground up into a paste. Both the fresh and paste products are served as a condiment for Japanese and Polynesian foods, especially: Sushi (fish and rice), Soba (buckwheat noodles)and Sashimi (raw fish).

Growing Wasabi

Propagation: Wasabi can be grown from seed reasonably cheaply. Tissue cultured plants are also available but they are more expensive. Plant division is also used but this can pass disease into the new crop.
Yields/ha: 10–15 t/ha
Time of maturity: Approximately 18 months following planting is the recommended harvest period.
Soil type: Moist, fertile soils are required.
Fertilisers: Slow release NPK fertilisers + trace elements.
Weed control: Weed control when the crop is immature is crucial. When the plants are older control is a little easier. Be careful using any herbicide around Wasabi. Hand weeding would be preferable.
Pest/Diseases: All pests that attack the cabbage/turnip family attack Wasabi e.g. Aphids, Phoma, Caterpillars.
Harvesting: Wasabi plants are harvested by hand and broken up to extract the exportable rhizomes and stems.
Marketing: For export, the stems should be green and have little discoloration from Phoma infection (a fungal disease). The fresh stems are highly sought after on the Japanese market.

Further Information

Wikipedia article