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Wasabi

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Bring the authentic flavour of Wasabi (Wasabia japonica) to your garden and kitchen! Known for its bold, spicy rhizome, freshly grated Wasabi offers a clean, aromatic heat that enhances sauces, stir-fries, salads, and more. The leaves and stems can also be used fresh in salads or stir-fries, adding a mild, peppery flavour. Wasabi thrives in cool, shaded, and consistently moist conditions with moderate humidity, making it a perfect choice for shaded garden beds, raised mounds, pots, or even planted near the edge of ponds. Its lush, heart-shaped foliage adds ornamental value to any space. Wasabi loves the shade and humidity, so it’s ideal for filling those tricky spots in your garden where light is limited. In 18–24 months, this unique perennial matures, providing a rewarding and delicious gardening experience that will elevate both your garden and your meals.

SKU: TCWASABI001 Category: Tags: ,

Description

Wasabi

Wasabi (Wasabia japonica, family Brassicaceae) is a cool-climate perennial native to Japan, prized for its spicy rhizome used to make authentic wasabi paste. Its distinct flavour differs from horseradish-based imitation. The rhizome sits at the base of the plant, surrounded by lush, heart-shaped leaves. The plant’s edible leaves and stems have a mild, peppery flavour, perfect for salads, stir-fries, or as a garnish.

Wasabi’s Natural Habitat & Climate Preferences

In its native habitat, Wasabi grows in shaded, rocky riverbeds with flowing water, making it ideal for shaded gardens or pots. It thrives in cool, moist, and shaded conditions, with temperatures between 8–20°C. While it can be grown in cool to mild tropical climates, Wasabi does best in cool, shaded environments with moderate humidity.

Ideal Growing Conditions

Wasabi requires moderate humidity, which can be maintained with misting, humidity trays, mulching, or by grouping plants together. It needs shade to protect it from direct sunlight, which can be provided by shade cloth, trees, or in shaded garden beds. Wasabi can be planted near ponds in shaded spots and should be shielded from intense heat in warmer climates. In these areas, Wasabi can be grown indoors in indirect sunlight.

Planting Time & Growth Cycle

Wasabi can be planted year-round, though the cooler months of autumn and winter align better with its natural growth cycle. It takes 18–24 months to mature, forming lush, heart-shaped foliage that adds ornamental appeal to shaded gardens or pots.

Planting Wasabi

Pots
Pots are great for areas that require Wasabi to be moved to adapt to climate changes.

  • Use a 30–40 cm deep pot with a free-draining mix (coco peat, sand, bark).

  • Mix in a small amount of compost.

  • Plant the rhizome shallowly, with the crown exposed.

  • Keep in full shade or filtered light.

  • Move indoors or into shelter during extreme conditions.

Raised Mounds
Raised mounds provide better drainage and air circulation for the rhizome.

  • Build a 15–20 cm high mound using loose, well-drained soil.

  • Position the rhizome shallowly at a 15–30 degree angle with the crown slightly above the soil.

  • Mulch lightly around the base to conserve moisture and stabilise temperature.

Watering

Wasabi likes consistently damp soil but must not sit in waterlogged conditions.

  • Water when the top few centimetres feel dry.

  • Always water at the base of the plant, avoiding overhead watering.

  • Ensure good drainage, especially in pots.

  • Reduce watering in cooler climates during winter and increase watering during dry spells in warmer areas.

Fertilising

Feed Wasabi once it’s actively growing to support rhizome and leaf development.

  • Pots: Use slow-release fertiliser every 3–4 months or liquid feed every 2–4 weeks.

  • In-ground: Fertilise in autumn and spring using compost or balanced organic fertiliser.

  • Vegan-friendly options include seaweed or plant-based fertilisers.

Winter & Frost Care

In cooler regions, Wasabi’s growth slows in winter.

  • Pots: Move to a protected area with indirect light.

  • In-ground: Use raised beds, mulch well, and apply frost cloth on frosty nights.

  • Avoid boggy spots or waterlogged soil.

Dry Air & Humidity

Wasabi enjoys humidity and may struggle in dry air.

  • Use a pebble tray with water, raised above the waterline.

  • Group potted plants to trap moisture.

  • Mist leaves gently during hot, dry days.

  • Use shade cloth or a natural canopy to protect from drying winds.

Harvesting

Wasabi rhizomes take 18–24 months to mature. Harvest when:

  • The rhizome is firm, bumpy, and 2–3 cm wide.

  • Part of the rhizome is visible above the soil.

  • The plant has dense leaves, and the lower foliage begins to yellow.
    Harvest gradually, using a fine-toothed grater for fresh wasabi paste.

Propagation

Wasabi typically lasts 3–5 years, after which its rhizomes may become woody and lose productivity, signaling the need for replacement. While propagation is possible, many gardeners replace rhizomes for optimal growth.

Storage

  • Don’t wash the rhizome before storing.

  • Store unwashed in a paper or ventilated bag in the fridge (crisper drawer).

  • Use within 14 days for the best flavour and texture.

  • If slicing: wash only the portion needed, then grate fresh before serving.

Grated wasabi loses its pungency within 15–20 minutes.

Pests & Diseases

  • Slugs/snails: Use pet-safe pellets or copper barriers.

  • Caterpillars: Remove by hand or apply BT spray.

  • Crown rot/mildew: Ensure good airflow, avoid overhead watering, and keep mulch clear of the crown.

Safety

Wasabi is non-toxic and fully edible. The rhizome, leaves, and stems can be safely eaten raw or cooked. Most pets avoid it due to its strong, spicy flavour.

Supplied as a dormant rhizome.

Additional information

Price Code

D – Purple Pack
Botanical Name

Wasabia japonica
Quantity in Pack

1 Rhizome
Planting Time

Plant from April onwards during the cooler months.
Planting Depth

When planting the Wasabi rhizome, place it at a gentle angle (15–30 degrees) with the top (crown) slightly exposed above the soil surface. The crown is the rounded, more prominent end of the rhizome, where the buds (growing tips) are located. The bottom will be flatter or more tapered, where the roots will grow. Ensure the growing tip is facing upwards to encourage healthy shoot development.
Planting Width

In the Ground:
When planting Wasabi in the ground, space the rhizomes 30–45 cm apart. This provides enough room for the rhizomes to grow and spread while ensuring they have access to nutrients and moisture. If planting in a row, make sure there is at least 30 cm between each plant to allow for healthy growth and root expansion.

In Pots:
For potted Wasabi, plant one rhizome per pot to give it enough space to establish and thrive. Ensure the pot is at least 30–40 cm deep with a wide diameter. This allows ample room for the rhizome to grow and for the roots to spread comfortably.
Soil

For in-ground planting, use well-draining, fertile soil rich in organic matter like compost. Regardless of whether your soil is clayey, sandy, or loamy, adding bark, perlite, or coarse compost helps improve drainage, soil aeration, and moisture retention. For potted Wasabi, use a free-draining potting mix enriched with organic matter such as compost or aged bark to maintain moisture while ensuring proper drainage.
How to Plant

Wasabi thrives in cool, shaded, and consistently moist conditions. Choose a shaded area in your garden for in-ground planting or place potted Wasabi in a cool, indirect light spot. Avoid direct sunlight and areas that experience heavy winds or extreme temperatures.

In the Ground:

Prepare the soil: Ensure the soil is well-draining and fertile. Mix in organic matter like compost, bark, or perlite to improve drainage and moisture retention.

Create a mound: Build a mound about 15–20 cm high to encourage proper drainage.

Plant the rhizome: Place the rhizome at a gentle angle (15–30 degrees), with the crown slightly exposed above the soil. Ensure the growing tip is facing upwards.

Space them: Plant rhizomes 30–45 cm apart to allow ample room for growth.

Mulch (optional): Apply 8–10 cm of organic mulch (like sugarcane, bark, or straw) around the plant to retain moisture, regulate soil temperature, and suppress weeds. Keep mulch clear of the crown to avoid rot. Mulching is best done in spring or early autumn, or in colder climates, it can be used in winter for frost protection.

In Pots:

Choose the right pot: Use a pot that is at least 30–40 cm deep and has good drainage holes.

Prepare the soil: Use free-draining potting mix, enriched with organic matter like compost or bark for moisture retention and drainage.

Plant the rhizome: Place the rhizome at a gentle angle (15–30 degrees) with the crown slightly exposed. Ensure the growing tip is facing upwards.

One rhizome per pot: Space rhizomes one per pot to give them room to grow and establish.

Mulch (optional): In pots, you can apply a thin layer of gravel or stones over the surface to help with moisture retention and to prevent crown rot.
Watering

In the Ground:

Water deeply to ensure moisture reaches the roots. The soil should stay consistently moist, not soggy.

Check moisture levels regularly, especially in warm weather. Avoid waterlogging by ensuring good drainage.

Mulch to retain moisture but keep it clear of the crown to prevent rot.

In Pots:

Water when the top layer of soil feels dry. Ensure water drains freely from the pot to prevent root rot.

Frequent watering may be needed, especially during warm weather.

Seasonal Tips:

Cool climates: Water less frequently in winter, when growth slows.

Warmer climates: Water more often during the active growing season, especially in dry or hot weather.
Fertilise

Wasabi is a light feeder and doesn’t require heavy fertilisation. Overfeeding can lead to leaf burn or slow rhizome growth, so it’s important to use fertiliser sparingly.

When to Fertilise:

Start fertilising once new growth appears, typically during autumn or spring.

Avoid fertilising during summer and winter when growth slows.

For Potted Wasabi:

Use a balanced, slow-release fertiliser (e.g., NPK 12:12:12) every 3–4 months, or apply liquid fertiliser (e.g., seaweed extract) every 2–4 weeks.

For In-Ground Wasabi:

Apply organic fertiliser (e.g., compost) in autumn and spring. Lightly mix in organic matter as needed to maintain soil nutrition.
Division

Wasabi can continue to grow for several years, but it is generally recommended to replace the rhizomes every 3–5 years, as their vigour diminishes over time. Signs of deterioration include reduced growth, woody texture, and lower rhizome productivity. While propagation is possible, many gardeners choose to replace the rhizomes periodically to maintain optimal growth and consistent performance.
Harvest

Wasabi rhizomes take 18–24 months to mature. During the plant's active growing period (spring and autumn), only the foliage should be harvested. The rhizome is left to grow until it reaches full maturity.
Signs Your Wasabi Is Ready to Harvest:

The rhizome should be firm and have a bumpy, textured appearance, similar to horseradish.

It should be about 2–3 cm thick at the base.

Some lower leaves may start to yellow — a natural sign the plant is focusing energy on the rhizome.

How to Harvest:

Lift the rhizome carefully with a fork or hand tool after the growing season has slowed down, typically in late autumn or early winter.

Harvest the whole rhizome if it’s mature. If you only need part of the rhizome, carefully cut or dig up the portion you want, leaving the rest to continue growing.

Remove any foliage and trim away excess roots.

Using the Rhizome:

Freshly harvested rhizome is best grated immediately to maintain its pungent, authentic flavour. Wasabi loses its heat within 15–20 minutes of grating.

Store the rhizome in a cool, dry place (or in the fridge) if you're not using it right away.

Can You Harvest Leaves?:

Leaves can be harvested during the growing season (spring to autumn). Only take a few leaves at a time to allow the plant to keep growing strong. The leaves are mildly spicy and can be used in salads, stir-fries, or as a garnish.
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