Growing wasabi is legendarily known as a difficult but rewarding task. But if you can meet the demands of a wasabi plant, you’ll receive bountiful edible wasabi for authentic Japanese cuisine flavor.
I once thought there wasn’t a need for the struggle of growing wasabi at home. I mean, why learn how to grow wasabi when I can buy some already prepared from the store? But wait! One day, I learned the wasabi paste products sold commercially in the US aren’t real wasabi!
Yep, it’s true; the spicy green gunk labeled wasabi paste isn’t from a wasabi plant.
It’s European mustard and horseradish dyed green with food coloring. If you feel as betrayed and mind-blown as I am at this cruel deception of horseradish and wasabi, it may be important for you to learn about how to grow wasabi on your own.
Wasabi Japonica Quick Care Guide
If you’re only here to see our dirty little secret on how to grow wasabi, we won’t pretend to put up a tease. So grab this quick care guide and be on your way.
|Growing Conditions||Wasabi Needs|
|Temperature||45℉ and 65℉ (7℃ to 18℃)|
|Humidity||90% to 95%|
|Harvest range||One to two years|
|Water||Daily waterings; twice daily in hot weather 3” to 4” weekly|
|Fertilizer||Once weekly with liquid 12-12-12 or compost tea|
|Soil||Well-draining, moist 6 to 7 soil pH, organically humus-rich sand, vermiculite, or gravel|
|Pests||Cranefly larva, alfalfa looper larva, aphids, and slugs|
|Diseases||Root rot, Petiole blight, rhizome rot, leaf spot|
But for those who prefer a more detailed explanation for a wasabi care guide, keep reading for a breakdown of each individual section for caring for wasabi.
Table of Contents
- How to Care for a Wasabi Plant?
- How to Harvest and Store Wasabi?
- What Are Wasabi Plant Problems?
- What Do I Need to Know About Wasabi?
- How Do I Plant Wasabi Seeds?
How to Care for a Wasabi Plant?
Wasabi is a notoriously complex plant to grow. Consequently, the most difficult part of wasabi plant care is trying to imitate the native conditions where wasabi grows.
Cool Temperatures and Shade Are King
Because wasabi naturally grows in mountainous regions, it requires cool temperatures that you normally can’t get in your home or outdoors in most zones.
You’ll need to control the temperature for optimal wasabi growth. The ideal range is between 45℉ and 65℉ (7℃ to 18℃). But mature plants can tolerate fluctuations between 27℉ and 80℉ (-3℃ to 27℃).
It also requires that you choose a fully shaded spot where it is completely protected from direct sunlight or bright light. Choose a natural tree canopy or create one with a tarp, sheet, or other shelters that provides 75% coverage.
North and East facing balconies make for great sheltered growing spots outdoors. And when you bring your plants indoors, they need to be placed near a window under full shade.
Cold Water and High Humidity
Wasabi plants require daily watering with cold water so the dirt and roots stay cool. During hot days, you’ll need to water your plants twice a day using cool or room temperature distilled or rainwater.
You can also position your plants near a source of constant water, like near lakes, riverbeds, or waterfalls. Growing these plants using aquaponics is also common.
Wasabi plants will not tolerate drying out from the top or the bottom. Besides keeping the dirt steadily moist, wasabi plants require high humidity of 90% to 95%. Check out our best plant humidifiers here.
The Soil Must Drain Well
To create better drainage, your wasabi plants will grow best in heavily amended garden soil mixed with perlite, peat moss, or leaf mulch. Besides being organic-rich, it should also have a loose, crumbly texture and good drainage.
The soil has to drain well to prevent the mix from becoming boggy. You can test the soil’s ability to drain before adding your plants. Pour one to two gallons of water through it to see if it will drain without getting sloppy. Coarse sand can help the dirt retain moisture without being too wet.
Frequent Fertilizing Is Helpful
Since you have to water Japanese horseradish plants so often, they do well with frequent dosing of a 12-12-12 fertilization. A liquid fertilizer mix with high sulfur is also beneficial.
A commercial feeding trick is to use a sulfur foliar spray on the plants one to three months before harvest to increase the flavor and spiciness. In other words, treat your plants with some Epsom salt.
Once weekly, treat your wasabi plants with homemade compost tea or liquid fertilizer to replace the nutrients they lose from watering. Well-rotted manure or compost can also add nutrients.
No Pruning Necessary, but Remove Damaged Leaves
You don’t need to prune wasabi plants to control their growth. But you should keep up with leaf removal of wilted, damaged, diseased, or dead pieces. Leaving a dead wasabi leaf to rot can encourage diseases and pests.
Propagation of Wasabi Plants
Propagating wasabi plants is better done from established plants rather than trying to develop plants from seeds.
You’ll need to harvest the baby specimens from the parent plant once the plantlets – offshoots – get 1 ½” tall, dark green, and with four to five leaves that don’t show any signs of disease or sickness.
Harvest the plantlets by cutting or pulling the offshoot from the stem. Once removed, plant the babies as you would seedlings, 2″ apart in a fertile mix of vermiculite, perlite, peat moss, and wet soil that is well-draining.
How to Harvest and Store Wasabi?
Wasabi should be ready to harvest in 1 ½ to 3 years. The stems, flowers, and leaves are harvestable once the plants reach 4″ to 6″ tall. The rhizomes and roots are also edible.
Trim off the roots and the leaves and scrape off the ridged nodes with a sharp knife before you grate your bounty. You can get a wasabi grater, but a cheese grater would work just as well.
It’s best to eat grated wasabi within 15 minutes. Unused portions can go in a crisper in the fridge if you wrap them in wet newspaper. Wasabi can also be dried and ground into powder for longer storage.
What Are Wasabi Plant Problems?
The notorious difficulty of wasabi growing means there are several problems you can encounter before your plants reach maturity after two years.
Wasabi root rot is one of the biggest issues with these plants, given their preferences for staying wet. However, ensuring your plants have the proper drainage can prevent the roots from rotting.
You can also experience issues with several kinds of pests. Keeping the plant in a cool spot can help prevent infestations from crane fly larvae, alfalfa looper larvae, aphids, and slugs.
It’s possible to remove minor infestations by hand. Be sure to squeeze the pests to squish them and prevent them from coming back.
If you’d prefer to repel insects without using chemicals or picking the insects off, you can douse the affected leaves with insecticidal soap. You can also spray the plants with neem oil. It will be necessary to remove severely infected, damaged plants.
Improper watering can cause wasabi plants to risk several fungal diseases. You might notice signs of leaf spot, rhizome rot, petiole blight, or root rot.
Most of these conditions result in similar symptoms, sometimes making it difficult to diagnose the illness. For example, your plants may experience stalks and roots that turn black or brown or leaves that turn grayish and wilt or develop small spots.
Treat your plants with a preventative copper spray to protect your plants from leaf spots.
What Do I Need to Know About Wasabi?
So, I’ve given you the cheater’s guide to caring for wasabi. But what the heck is it, and why would you want to grow a wasabia plant?
What is Wasabi?
The wasabi plant belongs to the Brassica family and goes by the scientific name Wasabia japonica. You may also hear it called Japanese horseradish. Wasabi is an entirely edible plant that has several health benefits.
Many people ask, where does wasabi grow? This edible plant is native to the mountains of Japan, often found growing near streams and rocky soil.
And many wasabi plant farms have also cropped up along streams and rivers in wet high-altitude mountainous climates with cooler temperatures of British Columbia and the Pacific Northwest. They prefer a steady source of water, full shade, and cooler temperatures.
Of the 18 wasabi varieties, the only two types typically found in the US are daruma or mazuma.
How Does Wasabi Taste?
The taste is similar to horseradish or hot mustard and is sometimes used as a substitution for chili peppers. However, the hot spicy taste quickly fades to a smoother, sweeter flavor than traditional horseradish.
This plant has high concentrations of polyphenol that provide anti-inflammatory properties. As a result, it can not only extend your health and longevity but also reduce brain neuroinflammation and nervous system activity.
What Does Wasabi Look Like?
Seedlings emerge from seed pods in loose soil and develop deep roots. Once the wasabi roots anchor the plant into the ground, it starts to form leaves.
New leaves form at the top of the fat swollen rhizome stems as old leaves age and fall off – molt – leaving behind scales – ridges.
As the plant ages, the stalk – rhizome – gets taller and thicker, up to 2 feet wide and 2 feet tall. Many plants end up resembling miniature palm trees with large heart-shaped bright green leaves that can be up to 24 inches long.
How Do I Plant Wasabi Seeds?
Another issue many gardeners experience when growing wasabi is how long the seeds take to mature into adult plants. When you grow wasabi plants from seeds, it can take eighteen months or longer before you can harvest your plants.
Wasabi seeds should be planted during late fall or early to mid winter, at least two months before the seeds sprout in February. They need cold temperatures to end dormancy. Or you can use an artificial cold treatment to force germination – such as keeping the Shimane or Daruma seeds in a refrigerator at – 41℉ (5℃).
Seeds should be left to soak in distilled water all night so the outer shell softens. Cracking the shell helps the seeds germinate faster.
Wasabi can grow in the ground, in raised flower beds, or containers if you need to bring the plants inside when temperatures get below 30℉ (-1℃). You can plant them outdoors or move the containers when the temperatures start reaching 50℉ to 55℉ (10℃ to 13℃).
Use raised flower beds to create 2 inch deep, 2 inch wide rows spaced 5 inches to 6 inches apart. Add one seed to each hole, cover with soil, and add plenty of water.
For container growing, use a 12” deep and wide container full of soil and sprinkle 15 to 20 seeds on top. An 8” deep and wide pot can be appropriate for smaller size and fewer seeds.
Push each seed 1″ to 2″ deep, 2″ apart. Then sprinkle the dirt with compost and top with chicken grit for protection from heavy watering.
Put the containers in a shady outdoor location when winter is in full gear or early spring. Give them enough water to moisten the dirt while waiting for the seeds to sprout – typically several months. Then, transplant the healthiest plantlets – pups – into bigger containers.
It’s better to purchase small wasabi seedlings that have already established roots. Plant wasabi babies with the root line raised slightly outside the soil level. Once you water your plants, they will settle down into the dirt.
But prevent covering any above-ground stem, which can lead to rotting. Instead, adding tiny pebbles as a mulch layer can help the dirt retain moisture. And it keeps plants from sinking further below the soil line when you water.
FAQ About Growing Wasabi
How long does wasabi take to grow?
It can take wasabi a year and a half to three years to grow from seed to harvest.
Is growing wasabi profitable?
Wasabi can be a profitable crop to grow due to the high costs – $160 to $300 a kilogram. But it’s not a get-rich-quick scheme. Harvesting wasabi and profiting from it are long-term goals that take several years to see a good return.
How do you start growing wasabi?
While it’s possible to start wasabi from seeds, you’ll get better odds of success if you start your wasabi crops from pups – baby plants.
Where does wasabi grow best?
Wasabi does best in climates that keep mild to cool temperatures.
Are You Ready to Grow Your Own Wasabi?
Wasabi can be an interesting plant to grow for gardeners who enjoy a challenge. But this edible plant is not for beginner gardeners or anyone who doesn’t have the time to devote to the many demands of this finicky beauty. So keep this informative wasabi grow guide handy if you decide you’re up for the task.
And share your success – or failures – with us, so we can rejoice in your achievement in growing the most difficult plant in the world.
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