Name: wasabi, Japanese horseradish, Wasabia japonica, Eutrema japonica.
Foliage: evergreen rhizomatous perennial with large, heart-shaped leaves up to 30cm.
Climate: prefers a humid environment in summer, with temperatures no lower than about 10°C and no higher than 20°C for much of the year. Best suited to the sub-tropics or tropics, although it can be grown in a sheltered microclimate or indoors in other areas.
Soil: improve soil with organic matter such as well-aged manure or compost prior to planting. If growing in pots, choose a premium potting mix with excellent water storage capacity, as wasabi prefers a moist soil.
Position: a shaded position with protection from wind, cold, sun and extremes of temperature. Self-watering pots are a good idea if growing indoors.
Flowering: small white flowers appear in spring. These are also edible, although they will only appear under ideal growing conditions.
Feeding: annual applications of well-aged manure are ideal.
Watering: water daily in warm dry weather. Wasabi is a water plant in its natural habitat, so needs to be watered regularly.
Wasabi is a lush evergreen perennial with large, heart-shaped leaves. The foliage makes a statement in the shade, while the rhizome can be harvested for cooking after two years. Wasabi plants are fragile, so avoid high-traffic areas, where breakages are more likely.
The wasabi rhizome is popular grated as wasabi paste, while the leaves make a spicy addition to salads. Flowers are also edible, and are traditionally served as tempura in Japan.
More than just an edible plant, wasabi is also a stunning indoor or water plant, best suited to shaded areas and indirect sunlight. It’s a perfect solution for dark, shaded areas under the canopy of other plants or in the shade of your home or neighbouring fenceline.
Propagation is usually by seed, although unless growing conditions are ideal, plants struggle to set viable seed. Wasabi is commercially propagated by tissue culture.
Water daily and protect from extremes of weather, including frost, heat or direct sunlight. Provide shade if required, or mulch to reduce the likelihood of frost damage. Applications of seaweed solution will help protect plants in winter and summer.
Treat for pests as soon as possible to prevent defoliation of the rhizome, which can dramatically set back growth and development.
Daily watering is required, unless your wasabi plant is grown beside a pond. Annual top-dressing with well-aged manure is usually enough, although additional applications of a seaweed solution will help improve plant vigour.
Snails and slugs adore wasabi’s spicy leaves, eating it to the ground at every opportunity. Protect your plant with a circle of snail and slug pellets.
Wasabi is a brassica (related to cabbage), so watch for cabbage white butterfly, caterpillars and aphids. If present, apply Derris Dust or spray with Dipel. As this is an edible plant, always use organic treatments to keep your plants healthy and pest-free.
Because wasabi likes water, a common mistake is to leave it wet. In a stagnant, waterlogged environment, wasabi is prone to rot. Good drainage and regular watering is best.
If using products to deal with pests, diseases or weeds, always read the label, follow the instructions carefully and wear suitable protective equipment. Store all garden chemicals out of the reach of children and pets.
Horseradish: a spicy rhizome that’s easy to grow and is often used as a substitute for wasabi.
Japanese ginger: an easy-to-grow rhizome that complements Asian cuisine.
Garlic: a culinary staple that is super easy to grow at home.
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