Wasabi is an evergreen perennial in the Mustard family, albeit one of the more sensitive and reclusive mustards on Earth. The plant is native to Japan and cultivated there extensively, often grown in pure cold water of stream or spring.
We find that the plant can readily be grown in good compost, as well. If watered frequently and kept in sun-dappled shade, the plants will flourish. Plants grown in this manner can be transplanted to stream, spring, or aquaponics, where they grow fast. The leaves are delicious, and a root big enough to dig, wash and grind for sushi can be attained in a couple of years. Somebody wanted to know how easy it is to grow from seed and I almost answered “easy,” then considered everything that goes into starting wasabi from seed and changed it to “potentially challenging.”
I had to keep the seeds semi-dried after harvest so they wouldn’t desiccate and dry. There’s a trick to that–you don’t want green, soft seed and you don’t want dry, hard seed. Somewhere in between. The seed was sown midwinter in rich soil in a cold greenhouse, and germination occurred after several weeks. I imagine that sowing the seed directly in warm conditions in a summer greenhouse would reap disappointment–you have to supply cold conditions to wake the seed. Then, there were the birds that got in the greenhouse and ate several of the germinating seeds. Perhaps they were treating a mild case of seafood poisoning, but it sure nipped my seedlings in the bud. I covered the flats with screen to keep out the birds, and then the slugs wanted to come up from below and have a snack, so I moved the flats to a slug-secure zone.
A few days of vacation on the coast meant I was not home to water the flats, and I think more seeds would have germinated if I hadn’t missed my date with the mister. But in the end, wasabi I had. The seedlings grew fast and made plants, so crisp, so green so very tasty–nothing quite like it!