How to Grow Wasabi Plants

Bright green rounded leaves with wrinkled surfaces in a container.

 Mike Wang / Flickr / CC BY 2.0

Wasabi, also known as Japanese horseradish, is the source of the hot, pungent seasoning popularly served with sushi, but also used to season nuts and other savory snacks.

Its strong taste and heat are well-loved by those who like spicy flavors. However, it has been said that some of the commercial wasabi served in restaurants is not 100% wasabi, but is cut with mustard or European horseradish and tinted with food coloring.

Adventurous cooks enjoy using wasabi too, and you can grow it in your own backyard. It prefers complete shade, so it is ideal for gardens that don't get a lot of sun, although it does have rather specific growing requirements.

The entire wasabi plant is edible. The thick stalk (actually a rhizome) of the mature plant is what is ground up for making wasabi sauce or paste. The stems and leaves are also edible and can be used in salads, soups, smoothies or stir-fry dishes. The stems can be chopped up like celery or chives to mix in with tuna or egg salad or to garnish potatoes.

Botanical Name Wasabia japonica
Common Name Wasabi, Japanese horseradish
Plant Type Perennial
Mature Size 24 inches tall
Sun Exposure Full shade
Soil Type Moist, rich, well-drained
Soil pH Neutral to slightly acidic
Bloom Time Spring
Flower Color White
Hardiness Zones USDA 8a to 10b
Native Areas Japan
Toxicity Non-toxic, all plant parts are edible
Wasabi leaves and rhizomes lying side by side on wooden surface
The rhizomes are the part of the wasabi plant used to make the pungent seasoning paste.  Valleybrook Gardens / Flickr / CC BY 2.0

Wasabi Care

Growing wasabi plants is moderately difficult because their growing conditions are so specific. There are a number of cultivars; "Daruma" and "Mazuma" are two of the most popular.

If planting in the ground, select a spot that remains in shade all day. It should not be too dry or too wet as wasabi will not grow in standing water.

Light

Direct sunlight is not tolerated well by wasabi, so make sure the plants are shaded. If you have to move your containers out of the sun you can do so, but it's much easier to create a shade barrier with fabric (shade cloth) or a folding screen. Alternatively, you can move the plants near a shelter where the sun won't hit them.

Soil

If growing in containers, use a one or two-gallon pot with a ten-inch planting depth. Mix up some rich soil with compost; slightly heavier than potting mix medium, so it will hold moisture. Plant your starts so that they stand upright, leaving part of the rhizome exposed.

Water

Water your wasabi well at planting and then regularly after this. Misting the plants will also help keep them cool. Take care not to overwater as these plants don't tolerate waterlogged conditions.

Temperature and Humidity

One important consideration for growing wasabi is that it tolerates only a narrow temperature range, preferring constant temperatures of 50-60 degrees Fahrenheit.

Temperatures below freezing (32F) or above 80F can kill the plant, so these extremes should be avoided. Some coastal locations like the Pacific Northwest provide suitably cool, temperate weather for growing wasabi. Planting in containers means you can move the plants if the thermometer suddenly gets too high or too low.

If the leaves get droopy or wilted, move the plants to shade and mist them a bit.

Pruning

Removing any wilted leaves that don't perk up after misting is recommended. This can help to avoid any spread of disease or powdery mildew.

Propagating Wasabi

Finding wasabi seeds may prove nearly impossible, as they are not easy to germinate. Most growers purchase "starts" from a reputable supplier and plant them.

Common Pests/Diseases

There are a few pests that may eat your wasabi. It's in the Brassica family and so any bugs that love to eat cabbage or broccoli, such as cabbage worms, will also enjoy munching on wasabi.

Remove slugs by hand, and aphids can be removed with a steady stream of water or a soft cloth. Make sure cool temperatures and shady conditions are maintained as this will help deter pests.

Insecticidal soaps are not recommended for wasabi. If any fungal disease is present, copper spray or baking soda spray can be used.

Harvesting Wasabi

You won't be able to harvest the rhizomes of your wasabi plants until the second year, so it's important to care for them attentively. The plants will be mature enough for pulling within fifteen months to two years. However, the plants will begin producing leaves within about eight weeks, so you can enjoy the bounty of your plants while you wait for the mature stalks. It's good to harvest these leaves to keep the plants neat and healthy.

After your first harvest, let the plant grow more leaves and harvest them every 6-8 weeks. If you can't eat them all, or give them to friends, the leaves can be blanched and frozen like any greens, or you can make a pesto-like sauce for pasta and rice and freeze it.

The stems can also be frozen, but are best eaten fresh. They're crunchy and make a good addition to stir-fry dishes or salads.