Wasabi

Sowing: Wasabi seed needs roughly two months of cold conditioning before it will sprout, so growers either sow in late fall to early winter or chill seed in a refrigerator, then soak it overnight in distilled water to soften the coat before setting one seed per hole, two inches deep, in rows two inches apart.

Siting and water: The plant wants loose, organic, free-draining yet moisture-retentive soil - coarse sand can open up a heavy mix - and does best in heavy shade or under a tree canopy where conditions stay cool, moist and humid, with air temperatures held roughly between 46 and 70°F (in flowing beds, water is kept closer to 46-64°F). Containers should be at least 10 to 12 inches deep and wide and stood in a shallow pan of water; keep the crop consistently moist but never sitting in stagnant water, and feed lightly with a slow-release 12-12-12 fertilizer that lasts three to four months. New plants can also be started by dividing rhizomes or detaching the plantlets that form around a parent plant.

Wasabi can be troubled by aphids, alfalfa looper larvae, cranefly larvae and slugs, along with leaf spot, root rot and rhizome rot. Removing wilted, damaged or dead leaves helps deter both the pests and the diseases that affect the crop.

Harvest: The rhizome is slow to size up, taking as long as three years to reach a harvestable diameter of about an inch, and is lifted by pulling the whole plant from the ground.

Storage: Flavour is best when the cleaned root is grated within thirty minutes of lifting, though rhizomes can be kept refrigerated for up to a month or dried and ground for longer keeping.

Culinary: The rhizome is finely grated into a thick green paste served with sushi, salads, poultry, sausage, steamed rice, soups and as a garnish for bread. Leaves, flowers, leafstalks and sliced rhizome are also preserved as the Japanese pickle wasabi-zuke, and young leaves are eaten raw in salads and sandwiches, though raw leaves can cause diarrhoea.

Historical: In Kamakura-period Japan (1185-1333), wasabi was recorded as a remedy said to support digestion, reduce inflammation, promote circulation and check bacterial growth, a use that predates its later pairing with raw fish in Edo-period sushi culture.

Wasabi is native to Japan, the Korean Peninsula and Russia's Sakhalin region, where it grows wild along cool mountain streams. The earliest record of it as a food dates to the eighth century, and cultivation in Japan is traced back at least to the Heian period (794-1185), well before it became the condiment now paired with raw fish.