Growing Real Wasabi
Real Wasabi is picky about its growing conditions.
Wasabi prefers cool, shady conditions and will sometimes thrive if left undisturbed in misty mountain stream beds. It generally requires a climate with average temperature between 8°C (46°F) and 20 °C (70°F), and prefers high humidity in summer. Since it is intolerant of direct sunlight, wasabi is typically grown under shade cloth or beneath a natural forest canopy.
Wasabia japonica grows in northern Japan, parts of China, Taiwan, Korea and New Zealand.
In North America, the rain forests found on the Oregon Coast and in parts of the Blue Ridge Mountains in North Carolina and Tenessee provide just the right balance of climate, sunlight and water quality to grow natural wasabi. Limited success has been achieved by firms using greenhouse and/or hydroponic techniques, but costs are higher. In Japan, highest prices are paid for all natural, water grown "sawa" wasabi.
Wasabia japonica plants are slow growing perennials with a rooted, thickened stem (rhizome), long petioles and large leaves. All parts of the wasabi japonica plant, including rhizomes, roots, stems and leaves are harvested, processed and valued for use. The rhizome stores the plant’s nutrients (similar to a potatoe) and is where the flavors tend to be most concentrated.
Wasabia japonoica plants can take as much as three years to reach maturity. Initially, given right conditions, the wasabi plant produces robust top and root growth, reaching approximate knee height (2 feet) with an overall width about the same. After this initial establishment phase the rhizome begins to build and store reproductive nutrients. It is this concentration of energy which produces the best nutrients so the rhizomes are generally the most valued plant part for neutraceutical purposes. All wasabi parts are valued for varied preparations in culinary use.
For table use, wasabi rhizomes are preferred at six to eight inches long and an inch or so in diameter. The appearance of the wasabi rhizome is similar to a brussel sprout stalk after the sprouts are removed. The long stems (petioles) of the Wasabia Japonica plant emerge from the rhizome to grow to a length of 12 to 18 inches and can reach a diameter of up to 40 mm (1 ½ in). They terminate into single heart shaped leaves that, in good conditions, can reach the size of a small dinner plate.
Wasabi leaves and leaf stems (petioles) tend to be brittle. Breakage or damage from animals, field workers or mishandling can cause plants to sulk and slow and sometimes even stop growth for periods of time.
Under optimum conditions, Wasabia japonica will reproduce itself by seed, but the resulting plantets can vary. Plantings can be extended by replanting small offshoots which characteristically occur as the plant matures. Commercially planted wasabi is propagated via tissue culture for uniformity and to ensure virus and disease free starts.