The wasabi, Also known as eutrema japonicum o Wasabia, is a plant native to Japan that has gained worldwide fame thanks to its potent spicy flavor and its importance in Asian cuisine. However, behind its culinary popularity lies a truly complex, delicate, and difficult-to-grow plant, which is little known in the West. In this article, you'll learn more about it. All the characteristics, cultivation, care and real uses of the wasabi plant, as well as the secrets that have made it one of the most expensive and valued ingredients in the world.
Origin, botanical description and varieties of wasabi
La wasabi plant It is a perennial species of the Brassicaceae family, like other plants such as mustard and horseradish. Its correct scientific name is eutrema japonicum (previously Wasabia), although it is also known as Japanese horseradish. Its origin is in Japan, especially in mountainous regions and humid valleys where it grows wild near streams with clean, cold water.
The plant reaches between 30 and 50 cm high, with broad, green, rounded, pointed, heart-shaped leaves that emerge directly from the central stem. Its main stem, which is actually the edible part known as the "rhizome" or "thickened stem," is between 10 and 15 cm long and about 5 cm thick. It is from this stem that authentic fresh wasabi is obtained after grating or grinding it.
The flowers of wasabi They are small, delicate, and white, clustered in bunches, and usually appear in spring. Although the entire plant is edible, the rhizome's greatest culinary value lies in its edible variety. The best-known commercial varieties are 'Daruma' and 'Mazuma,' although there are different cultivars adapted to different areas of Japan and now also to countries such as China, New Zealand, the United States, Spain, and Chile.
Why is wasabi so difficult and expensive to grow?
Wasabi is popularly known as "Japanese green gold«. This nickname is not accidental, but rather reflects his high price on the international market, which can range from $200 to $300 per kilo of fresh rhizome, even exceeding that figure in gourmet markets.
This is because the Wasabi cultivation is exceptionally complicated and requires extremely precise environmental conditions:
- Constant and cool temperatures, preferably between 8 and 20 ° C, although the optimum growth varies in the literature between 10 and 15-18 ºC depending on the variety.
- High humidity and irrigation constant but never waterlogged.
- Absolute protection from direct sunlight (which burns the leaves) and from severe frost or sudden changes in temperature.
- Roots should be left in clean, oxygenated water (ideal in mountain streams) or grown in moist, rich substrates with perfect drainage.
- A soil or substrate rich in organic matter, slightly acidic (pH 6-7), with good ventilation.
The development of the rhizome is very slow: normally needs Between 18 and 36 months to reach an ideal size for harvest. During this time, it is essential to maintain constant humidity, temperature, and nutrition, monitoring for pests such as snails, slugs, aphids, and fungal diseases caused by excess moisture.
For these reasons, few farms outside of Japan have managed to produce authentic wasabi with commercial success, although there are projects in Canada, Spain, Chile, China, Australia, and New Zealand.
Nutritional facts and health benefits of wasabi
Wasabi is not only a famous condiment, but nutritionally it is an interesting and healthy food:
- Water: 31,7 g
- Energy: 292 Kcal
- Carbohydrates: 46,13 g (of which 13,2 g are sugars)
- Fiber: 6,1 g
- Fat: 10,9 g
- Proteins: 2,23 g
It contains vitamin C in significant amounts, as well as minerals such as potassium, calcium and magnesium. Its bioactive compounds also stand out, especially isothiocyanates, which are responsible for the spicy flavor and characteristic aroma, but also have properties antibacterial, anti-inflammatory, digestive and antioxidant.
The isothiocyanates in wasabi have been shown in studies to act against Helicobacter pylori (bacteria associated with gastritis and digestive ulcers), limit the proliferation of some types of bacteria and may help prevent blood clots. Other benefits include boosting immune defenses and potentially preventing the development of tumor cells, although studies are still ongoing in this regard.
What part of wasabi is actually used?
There is a popular misconception that wasabi root is used, when in fact the rhizome or underground stem It is the most prized part in cooking. The rhizome is grated just before consumption, producing a paste with an intensely spicy and fresh flavor that is widely used in sushi, sashimi and other traditional Japanese dishes.
However, the entire wasabi plant is edible:
- Fresh leaves: They can be used in salads, soups, as a garnish or even smoothies.
- Stems: They can be chopped and added to salads or stir-fried dishes.
- Flowers: In Japan, they are sometimes pickled and used as a gourmet snack.
In authentic Japanese restaurants, fresh wasabi is grated with a sharkskin grater (oroshiki) to obtain a paste that should be consumed within a few minutes, as the flavor and aroma are quickly lost through oxidation.
Due to cost and difficulty issues, in most parts of the world a imitation wasabi, made with horseradish (rustic armor), mustard, green food coloring, and starch. Real wasabi is served only in high-end restaurants.
How to differentiate authentic wasabi from fake ones?
El authentic wasabi (Eutrema japonicum) and "false wasabi" or horseradish (rustic armor) share a certain spicy flavor profile due to the isothiocyanates, but have important differences:
- Color: Real wasabi is naturally green; fake wasabi is white and has added coloring.
- Flavor and smell: Real wasabi has a fresh, more fleeting and complex heat, with sweet and herbal nuances; imitation wasabi is more aggressive and persistent.
- Price: The real one is much more expensive (it can cost over €200 per kilo), while the fake one is very affordable.
- Availability: The authentic one is only found in exclusive restaurants or specialty stores.
In Japan, horseradish is called "Western wasabi." Most of the green paste sold as wasabi contains almost no real wasabi.
Main uses of wasabi in cooking and traditional medicine
Wasabi stands out in cooking as spicy condiment for sushi, sashimi, tempura, noodles, and fish or meat dishes. It is also used in sauces, aromatic oils, dressings, and snacks (peanuts, peas, or broad beans coated with wasabi powder). Its flavor-enhancing properties are accompanied by antibacterial properties, which is why it has traditionally helped to preserve raw foods before the era of the refrigerator.
In Japanese folk medicine, wasabi has been used as digestive, anti-inflammatory and antiseptic. Sometimes the stems are used to make a natural toothpaste.
Where and how wasabi is grown: conditions and techniques
In Japan, wasabi grows along mountain streams, in shady, protected areas with clean, constantly moving water. Outside of Japan, it is grown in greenhouses or hydroponic systems that attempt to replicate these conditions. Key steps for successful wasabi cultivation include:
- Location: cool, very humid location, without direct sunlight; semi-shade under trees or netting is ideal.
- Substratum: soil or mixture for acidophilic plants/urban gardens, with pH 6-7, abundant organic matter and very good drainage.
- Irrigation: Keep the substrate moist, but not flooded. The water should preferably be lime-free to avoid altering the pH.
- Hydrogen peroxide supply: If grown hydroponically, circulation and oxygenation are essential to prevent the roots from suffocating or rotting.
- Temperature: Protect from severe frost and intense heat (the plant may die above 25-30°C). In a pot, it can be moved if temperatures rise or fall too much.
- Fertilization: Feed regularly with compost, guano, worm castings or balanced organic fertilizer every 6-8 weeks during growth.
- Sun protection: In case of risk, shade mesh can be used.
Reproduction and multiplication of wasabi
Wasabi can be propagated primarily by seed (in spring), although it is also possible from rhizome cuttings. The most common method is by seedling:
- Prepare a tray with specific substrate, ensuring good drainage.
- Moisten the substrate before placing a maximum of 2 seeds per socket.
- Lightly cover the seeds with a thin layer of soil and keep the seedbed in the shade, with the soil moist.
- Seeds need to be soaked before planting to improve germination.
- Seedlings will appear in about 2-3 weeks if the temperature remains cool.
Transplanting to the final soil or a larger pot should be done when the roots fill the container. It's important not to damage the root ball to avoid stress or stunted growth.
Common pests and diseases
Wasabi is sensitive to pests such as snails, slugs, aphids and cabbage worms (because it is Brassicaceae). To protect the plant:
- Placing the pot in a bowl with a few centimeters of water prevents snails and slugs from accessing it.
- Eliminate aphids manually or with pressurized water.
- Avoid using chemical insecticides and soaps, as they are harmful to wasabi.
- For fungal diseases, use copper sprays or baking soda in case of fungal symptoms.
The best prevention is to maintain humidity, ventilation, and cool temperatures.
Harvesting and preserving wasabi
The wasabi rhizome takes between 18 and 36 months to grow to an optimal size for harvest. Harvesting is when the stem reaches approximately 15 cm in length and 4–5 cm in diameter.
After harvesting, the rhizome should be washed thoroughly and kept refrigerated. To fully enjoy its aroma and flavor, it is recommended to grate it just before eating.
The leaves and stems can be harvested in stages every 6-8 weeks starting in the second year. If not consumed fresh, they can be frozen or prepared into a pesto-like sauce for preservation.
- Why does wasabi sting? Its heat is due to isothiocyanates, which stimulate the nasal passages more than the tongue, producing an intense but short-lived effect. Unlike the capsaicin in chili peppers, it is quickly eliminated when eaten or drunk.
- Where is it grown outside of Japan? In addition to Japan, cultivation has been achieved in Canada, Spain, Chile, the United States, Australia, China and New Zealand, albeit on a small scale.
- Why is authentic wasabi so expensive? Its delicacy, the length of its cultivation, and the enormous difficulties in replicating natural conditions make the rhizome an exceptional product.
- Can it be grown at home? Yes, with patience, partial shade, and stable temperatures, it is possible to grow in pots if you take good care of the substrate, humidity, and sun protection.
The wasabi plant is much more than a spicy condiment for sushi. It's a botanical gem of demanding cultivation, requiring dedication, knowledge, and patience, capable of providing flavor, medicinal properties, and unparalleled gourmet value in the kitchen. If you decide to venture into its cultivation, you'll face a challenge, but also the satisfaction of harvesting one of the most exclusive ingredients on the planet, straight from your garden or terrace.
