Wasabi (Wasabia japonica) is one of the most unique challenges a gardener can face. The plant’s requirements are specific, but mastering the wasabi growing conditions and preparing your meals with fresh wasabi will make it all worth it!
Wasabi, also known as Japanese horseradish, is the most well-known condiment for sushi. Unfortunately, the product served is usually a mix of mustard, horseradish, and food colouring. Wasabi is well known for its finicky growing requirements, which emulate the conditions of its natural stream bed habitat in the rain-soaked mountain areas of Japan.
Understanding Wasabi Growing Conditions
Wasabi is found to grow well in a humid temperate climate where the temperature is 8°C to 20°C (45°F to 70°F), although if the plants rise to over 20°C, they will wilt. Shady growing conditions are preferred, and they are found to grow naturally in the shaded areas of the forest, where they get filtered sunlight. Access to a plentiful supply of good quality, clean and fresh (un-chlorinated) water is also essential.
Choosing the Right Site and Soil
Selecting Your Planting Site and Preparing Your Soil. Site selection is critical to the success of growing wasabi. Lengthy periods of direct harsh sunshine are not conducive to healthy Wasabi plants. Therefore, select a site that will offer your wasabi at least partial shade for most of the day, or use a shade cloth to mimic the dappled sunlight conditions common to a forest canopy. The planting site should have rich, moist, well-drained soil with a pH of 6 and 7. Adding organic matter, such as compost, to the garden soil will help improve soil structure and fertility. Loose, well-aerated, friable soil will provide the perfect growing medium for the Wasabi plant’s rhizomes.
Water Requirements
One of the most challenging yet most important things about growing wasabi is mimicking its natural habitat. The optimum water requirements for wasabi require the soil to be constantly moist but not waterlogged. To achieve this, some growers use a hydro system to maintain sufficient moisture levels; others even use drippers to simulate a natural stream. Some may even mulch the surface of the container growing to prevent rapid evaporation from the surface of the soil. If this plant is grown the traditional way in the ground, again, it is useful to mulch the ground; this will also reduce the temperature of the soil.
Propagation
Wasabi is primarily grown from offsets or tissue-cultured plantlets. It can be raised from seed, but this is not the best way to get started because seedlings are slow-growing and take 1 – 2 years to develop their first rhizome. The offset is one or more small rhizomes produced on the plant yearly. Mix much well-rotted compost and/or rotted cow manure with the soil before planting, place the offset in at the same depth that it was originally growing, water well, and spread a layer of hay mulch around the plant and less water daily until it establishes. Tissue-cultured plantlets are much larger than seedlings and will also have more than one leaf. Again, prepare the soil as you would for an offset, place the wasabi at the same depth it was grown, water well, and add mulch and less water daily until established.
Planting
The best time to plant is in Spring or Autumn to avoid the extreme heat of summer and winter cold. Allow about 30 cm between plantings to allow the group and to allow good air movement.
Maintenance
Weeding is crucial to wasabi as they don’t compete well with the weeds. Just take care not to disturb the tiny roots when removing the weeds. Apply a well-balanced, slow-release granular fertiliser for a long, steady feed, not short, sharp, dangerous effects fertilising that will burn the plants. Avoid over-fertilising, which will burn the plants. Pests and diseases can also be a problem, particularly in humid conditions. Keep an eye out for problems such as slug and snail damage, aphids (a blast from the hose will wash the aphids away), and fungal diseases. If necessary, treat organically or use recommended treatment options. Don’t use harsh chemicals as they may scar or reduce the quality of the wasabi’s great flavour.
Harvesting
Wasabi plants take 18 to 24 months to mature, so a relatively high amount of care is needed. The part of the wasabi plant we use is the rhizome. After 18-24 months’ growth, wasabi is carefully dug out so that rhizomes, not roots, are taken. Typically, most of the leaves and stems are still left so they can continue growing. Harvested rhizomes can be either cleaned directly or can be dried slightly and ground out on needed bases. The bright, fiery flavour of fresh wasabi is subtler than the reconstituted powder or the paste forms most people are used to.
Challenges
Growing wasabi isn’t a garden project that is instantly rewarding. With a growing season of up to two years before it can be harvested and exacting growing conditions, it’s definitely a project for those with a lot of patience. The plants are fussy and the temperature, sunlight, or water conditions aren’t just right, the wasabi will grow poorly, and the flavour will be mediocre, at best. On the other hand, good wasabi can deliver an incomparable aromatic flavour, a fresh and grassy taste, and a faint tongue tingle. Adding it to a recipe where real wasabi is allowed to shine is an opportunity to elevate the dish to the next level.
Conclusion
While growing and having wasabi is not the easiest gardening, growing wasabi is very rewarding. You can harvest fresh wasabi by carefully matching the plants’ natural planting conditions as closely as possible, strictly monitoring and managing their growing environment, and tirelessly waiting until the wasabi matures. You, too, can have your very own fresh wasabi at home, knowing it is real wasabi and not some horseradish and mustard concoction.
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I’m Sofia Kitson, the Wasabi Crop Blogger. My interests are writing articles on growing and cooking with wasabi.