How to Grow Wasabi

Creating the Right Conditions

Locate an environment that's humid and temperate. Wasabi is native to Japan, and grows best in a wet, warm climate between 45 °F (7 °C) and 70 °F (21 °C). Wasabi is notoriously finicky and will not grow in places where the temperature routinely rises or falls out of this small range. Wasabi naturally grows in wet, wooded areas with plenty of moisture in the air and well-draining soil. In the USA, parts of the Pacific Northwest and the Blue Ridge Mountains have the right conditions for growing wasabi. Few other places are naturally suitable for growing the plant.

Consider temperature control solutions. If you live in a region that doesn't have the natural climate necessary for growing wasabi, you will need to recreate the right conditions manually. One of the best ways to do so is by using a greenhouse, which traps heat and humidity and allows you to control the temperature. If you decide to use a greenhouse, adjust the settings so that the temperature is always between 45 and 70 degrees Fahrenheit. If you live in a place where the growing conditions are fairly close to what wasabi naturally needs, you may be able to get away without using a greenhouse. If you live in a hot region, use a tarp or sheet to shade the planting bed so it won't get too hot. If you live in a place with mild cold snaps, cover the plants when the temperature gets cold.

Pick a well-shaded spot. Wasabi does not do well in direct sunlight; it needs a very shady spot. In the wild, wasabi grows under forest canopy, where just enough sunlight filters through the leaves to give the wasabi what it needs to flourish. As a home cultivator, try to replicate this environment either by planting the wasabi under trees or using a hand-fashioned canopy to shade the growing bed. In a greenhouse, it's still important to make sure the wasabi gets plenty of shade. Situate the wasabi under taller plants or near shaded windows to make sure it isn't struck by direct sunlight.

Amend the soil. Use a mixture of compost and organic, sulfur-rich fertilizer. Till the soil to a depth of 10 inches (25.4 cm) and work in ten inches of compost to create a rich, healthy soil. Test and adjust soil pH until it falls between 6 and 7. This specific pH creates the best environment for wasabi. You want a very rich, organic soil with just the right pH to give your wasabi the best chance of surviving in a home setting. Follow label instructions when applying fertilizer.

Make sure the soil drains well. Wasabi likes to be kept moist, but not muddy and waterlogged. To check whether the soil drains well enough, water the area well and watch the water soak in. If it's slow to be absorbed, work in more compost. If it drains right away, the soil is fine for wasabi. Planting wasabi near a natural pond or stream is a good idea, since the soil will stay constantly moist, but will naturally also drain well. You could also plant wasabi near a waterfall that will continuously splash on the plant to provide water.

Planting and Caring for Wasabi

Order seeds in late fall. Wasabi seeds are difficult to source at local nurseries, so most people order them online. Late fall is the best time to order seeds; wasabi needs the winter to establish good roots. When the seeds arrive, keep them moist and plan to plant within 48 hours of receipt.

Plant the seeds. The night before you plant them, place the seeds in a small bowl and cover them with distilled water. Soak the seeds overnight prior to planting. Soaking will help to soften the seed shells and make it easier for the wasabi to germinate. Sow the seeds one to two inches apart and press them lightly into the soil.

Keep the soil and seedlings moist. Wasabi is a semi-aquatic plant that must be kept wet to flourish. Every day, mist the soil and the sprouting seedlings with fresh, cool water to emulate splashes from natural water sources, like a stream or waterfall. If the wasabi is allowed to dry out, it will begin to wilt. A micro-irrigation system is a good alternative to misting. Watch your plants for wilting (not enough water) and root rot (too much water), and adjust your irrigation accordingly. Because wasabi must be kept wet, it is susceptible to mold and disease. If you see a plant become diseased (wilted and discolored), pull it out right away to prevent it from spreading to other plants. Do not soak the soil or plants with a hose or watering can, as this increases the chance of rot and disease.

Weed the planting beds. Weed out competing plants so the wasabi roots have plenty of room to grow. Since the soil is kept moist on a daily basis, weeds tend to sprout quickly. Weeding every day or every other day will keep the problem under control.

Harvesting and Using Wasabi

Care for the plants for two years before harvest. Wasabi doesn't develop its distinctive flavor until it becomes mature after about 24 months. During this time the wasabi will grow about two feet tall and two feet wide. It will stop getting taller and wider, and start putting energy into growing a long, carrot-like rhizome beneath the soil.

Dig the mature rhizomes. Rhizomes are mature and ready to eat when they're about seven or eight inches long. Dig up one rhizome to check the length before completing the rest of the harvest. Use a long, slim spade or pitchfork and take care not to cut the rhizomes when you dig it out.

Leave some plants in the ground to self-seed. Wasabi left in the ground will produce new seeds and drop them into the soil, saving you the trouble of ordering more seeds. Leave several plants in the ground so you'll have a fresh crop of wasabi in the next couple of years. When the new plants begin to sprout, space the seedlings about 12 inches (30 cm) apart so they have plenty of room to grow. If you leave them in clumps, many will wilt and die.

Use the wasabi. Clean the wasabi rhizomes and discard the leaves. To enjoy wasabi's fresh, sharp flavor, shave off as much as you need and leave the rest of the rhizome intact. The heat of the wasabi will fade after a few hours, so it's best to cut off only as much as you need for one meal at a time.

Store wasabi for later use. Fresh wasabi will keep in the refrigerator for about a month or two before it begins to rot. If you want to save wasabi for later use, it's best to dry it out and grind it into a powder. The powder can be mixed with a little water to form wasabi paste.