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Wasabi (Eutrema japonicum)
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Growing and Maintaining Your Own Wasabi Plants in the UK: A Comprehensive Guide

Wasabi has long been associated with traditional Japanese cuisine. However, the cultivation of this prized plant is not strictly confined to Japan. With the right conditions and care, you can learn how to grow, keep, and look after your own Wasabi plants right here in the UK.

What is Wasabi?

Wasabi, also known as Wasabia Japonica, is a member of the Brassicaceae family, closely related to horseradish and cabbages. The plant is typically grown for its rhizome, which, when grated, produces the green paste often served with sushi.

Despite its reputation as a temperamental plant, Wasabi can be successfully grown in the UK's temperate climate.

Understanding Wasabi Growth Conditions

Wasabi is native to the mountainous regions of Japan, where it naturally grows in shady, humid areas alongside streams. Replicating these conditions is key to successfully growing and keeping Wasabi in the UK.

Temperature and Humidity

Wasabi plants thrive in temperatures between 7°C and 21°C. They can survive temperatures down to -5°C, but it's advisable to protect the plant with a straw or fleece cover during particularly cold nights. The plant also requires high humidity, making it an ideal candidate for greenhouse cultivation.

Light and Shade

Fresh Wasabi prefers low light levels, much like it experiences under the canopies of the forest in its native habitat. Therefore, a shady spot is essential for successful Wasabi cultivation. Placing it under overhanging branches, behind a tall bush, or on the shaded side of a fence or wall would be ideal.

Soil and Water

Wasabi prefers well-draining soil rich in organic matter. Maintain a soil pH between 6 and 7 for optimal growth. As a semi-aquatic plant, Wasabi needs constant moisture but should not be waterlogged. Incorporating drainage holes, regular misting, or a micro-irrigation system can help maintain the right moisture level.

Planting Wasabi

Growing Wasabi plants can be a rewarding process, though patience is required as it can take up to two years for the plants to mature. Here's a step-by-step guide to growing your own Wasab plants:

Weeding: Weed the Wasabi patch regularly to prevent competition for root space.
Caring for the Plant: Regularly check plants for signs of wilting (under-watering) or root rot (over-watering). If any plants appear diseased, remove them immediately to prevent the disease from spreading.

Harvesting and Using Wasabi

The reward of growing Wasabi comes after a two-year cultivation period, during which the plant develops its distinctive flavour. The wasabi rhizomes are ready to harvest when they reach around 7-8 inches in length.

Harvesting involves carefully digging up the entire plant and separating the rhizomes. The rhizomes can then be grated to produce fresh wasabi paste, adding a unique, zesty flavour to your dishes.

Multiplying Your Wasabi Supply

Once a wasabi plant is two or more years old, it can be divided into multiple plants. This process not only offers the opportunity to increase your Wasabi supply but also serves as a means of plant propagation, ensuring a continuous supply of this distinctive herb.

Wasabi Plant Aftercare

After harvesting, it's possible to leave some plants in the ground to produce new seeds. These seeds will drop into the soil, sprouting fresh wasabi plants the following year. This process can help maintain a consistent supply of Wasabi in your garden.

Challenges in Growing Wasabi

While Wasabi cultivation can be rewarding, it's not without its challenges. The plant is susceptible to pests and diseases, particularly when waterlogged. Regular monitoring and prompt action can help keep these issues at bay, ensuring a healthy crop of fresh Wasabi.

Growing Wasabi in the UK requires patience, care, and a good understanding of the plant's needs. With the right conditions and care, you, too, can enjoy the unique flavour of homegrown Wasabi. Whether you're looking to add a unique flavour to your dishes or simply enjoy the challenge of cultivating this distinctive plant, learning how to grow Wasabi can be a rewarding endeavour.

"Patience is a virtue with Wasabi, and the reward of harvesting and grating your own fresh wasabi paste will be all the sweeter for the two years it can take to yield the famously pungent rhizomes."

Frequently asked questions about growing Wasabi in the UK

Can I grow Wasabi in the UK?

Yes, we are cultivating Wasabi in the UK, but it demands particular conditions to flourish, similar to its native environment along stream beds in Japan's mountain river valleys.

To grow Wasabi in the UK, here are some vital considerations and steps:

Climate Considerations:

Temperature: Wasabi prefers a climate with temperatures between 8°C and 20°C. It does not tolerate extreme heat or frost.
Humidity: High humidity levels are beneficial for Wasabi.
Shade: Wasabi plants need protection from direct sunlight. They grow best in partial to full shade.

Soil and Water Requirements:

Soil Type: The soil should be rich in organic matter and well-draining. A pH between 6 and 7 is ideal.
Water Quality: Clean, constant, and cool water is essential, mimicking the plant's natural habitat. If possible, a water source that allows for a flow-through system can be beneficial.

Steps to Grow Wasabi in the UK:

Choose the Right Location: Find a spot that mimics the Wasabi's natural environment—shaded, cool, and humid.
Prepare the Soil: Amend your soil with plenty of compost to ensure it is rich in organic matter.
Planting: You can start Wasabi plants from tissue-cultured plants, or offshoots from mature plants. Plant them in the ground or in containers that allow for good drainage.
Watering: Keep the soil consistently moist but not waterlogged. If you are not using a flowing water system, water regularly to maintain the necessary moisture level.
Feeding: Fertilise with a balanced, slow-release fertiliser that is rich in nitrogen.
Protection: Use shade cloth to protect the plants from too much sunlight and to maintain humidity.
Pest and Disease Management: Be vigilant about slugs, snails, and some fungal diseases that can affect the plants. Use organic pest control methods where possible.

Harvesting:

Wasabi typically takes about 18 months to 2 years to mature enough for harvest.
The entire plant, including leaves, stems, and rhizomes, is edible.

Challenges:

Pests and Diseases: Wasabi can be prone to pests and diseases such as aphids and mildew, especially in a non-native environment where it may lack natural resistance.
Weather: Sudden changes in temperature or unexpected frosts can damage or kill the plants.

Although it's a challenge to grow Wasabi in the UK due to its precise requirements, it's entirely achievable with meticulous planning and management. Establishing the right environment is essential for the successful cultivation of Wasabi in the UK, offering a rewarding pursuit for those keen on speciality crops.

How long does it take to grow Wasabi?

Wasabi Cultivation Timeline

Here's a brief overview of the growth timeline for these plants:

Seedling Stage: Wasabi starts as either a seedling or a rhizome cutting. If grown from seed, germination can take up to 8 weeks, and the resulting seedlings are often transplanted to a growing bed after they are sufficiently established.
Maturation Period: Once transplanted, wasabi plants typically take about 18 to 24 monthsto reach maturity, which is when they can be harvested. This timeframe can vary depending on the growing conditions.
Harvesting: The part of the wasabi plant that is most commonly used is the rhizome. It is harvested when it is about 2 to 4 inches long and about 1 inch in diameter.

Wasabi plants necessitate a shaded, moist habitat with proper aeration and drainage, and they have a preference for cool temperatures. These conditions are naturally present in the mountain stream beds of Japan, making Wasabi a challenging plant to cultivate in non-native settings. To simulate these conditions, commercial growers outside Japan often employ hydroponic systems.

Can you grow Wasabi in a pond?

Indeed, fresh Wasabi can be grown in a pond, but it must have very specific conditions to prosper. Wasabi (Wasabia japonica) is indigenous to stream beds in the mountain river valleys of Japan, and water cultivation methods like pond growing aim to replicate these natural conditions. Here's a strategy for growing fresh Wasabi in a pond environment:

Site Selection and Preparation:

Shaded Environment: Wasabi prefers a shaded environment as it does not tolerate direct sunlight well.
Cool Temperatures: Ideal temperatures for Wasabi are between 8°C and 20°C (46°F and 68°F). Temperatures above 24°C (75°F) can hinder growth or kill the plants.

Water Conditions:

Clean and Oxygenated Water: The water should be clean, free of pollutants, and rich in oxygen. Running water is ideal because it is naturally oxygenated. Frozen water may damage or kill the plants.
Slight Acidity: Wasabi thrives in slightly acidic conditions with a pH of around 6 to 7

Planting:

Substrate:A gravel or large river sand substrate can help anchor the plants and allow for proper water flow.
Spacing:Space the plants to prevent overcrowding, which can lead to disease and poor growth.

Cultivation:

Water Depth:The water should be shallow enough to cover the roots but not so deep as to cover the entire plant.
Nutrients:Wasabi requires a nutrient-rich environment, so the addition of appropriate water-soluble fertilisers may be necessary.
Maintenance:Regularly check and maintain the water flow and quality to prevent stagnation and the buildup of harmful pathogens

Harvesting:

Maturity:Wasabi typically takes about 18 months to 2 years to reach maturity when grown in water.
Harvest Carefully:When harvesting, be careful not to disturb the surrounding plants and the root system.

The cultivation of fresh Wasabi can be difficult due to its need for particular growing conditions and its sensitivity to environmental stress. Nonetheless, with an appropriate setup and diligent care, growing fresh wasabi in a pond can be a fulfilling challenge for gardeners seeking a distinctive horticultural project.

How often can you harvest Wasabi?

Harvesting Wasabi

Fresh Wasabi (Wasabia japonica) is a challenging plant to grow and requires specific conditions to thrive, such as cool temperatures, high humidity, and constant access to water. It is often cultivated in aquatic conditions or in well-drained, gravelly soil to maintain its freshness.

Growth Cycle:Wasabi typically has a slow growth cycle. It can take about 18 to 24 months for wasabi plants to mature enough to be harvested.

Harvest Frequency:Once mature, the wasabi plant's rhizome (the part most commonly grated for use) can be harvested. However, since the plant takes a long time to reach maturity, it is not something that can be harvested frequently like many other crops.
Harvesting Method:When harvesting, the entire plant is usually lifted from the soil, and the rhizome is cut from the roots and leaves. The leaves and stems are also edible and can be harvested more frequently, often several times during the growing season.

It's worth noting that a wasabi company specialising in commercial wasabi cultivation requires expertise to ensure that plants reach maturity and are of high quality, as the market for the wasabi company's fresh Wasabi can be quite particular.

Are Horseradish and Wasabi the same plant?

No, horseradish and wasabi are not the same plant. They are, however, both members of the Brassicaceae family, which also includes mustard, cabbage, and broccoli. Despite their similar taste profiles, they come from different plants:

Horseradish is derived from the plant Armoracia rusticana. It is commonly used in the West and is known for its strong, pungent flavour. The horseradish plant has large, elongated leaves and is cultivated for its large, white, tapered root.

Wasabi comes from the plant Eutrema japonicum (formerly Wasabia japonica), which is native to Japan. Real Wasabi has a more complex flavour compared to horseradish and is often described as being more "herbaceous" and less harsh. The wasabi plant is much smaller than the horseradish plant and can be difficult to grow, which is why it is much more expensive.

In many cases, what is served as Wasabi outside Japan is actually a mixture of horseradish, mustard, starch, and green food colouring since real Wasabi is rare and costly. Those looking to buy Wasabi should be aware of this common substitution.

Where are the best places to plant Wasabi in the UK?

The wasabi plant in the UK is a challenging crop to grow, as it requires specific conditions to thrive. However, it can be successfully cultivated with careful site selection and management. Here are some factors to consider when choosing the best place to plant Wasabi in the UK:

Cornwall and Devon: These regions have a milder climate and may be suitable for wasabi cultivation due to their temperate conditions.

Scotland: Parts of Scotland, particularly the western and northern regions, may also offer suitable microclimates for growing Wasabi.

Wales: The climate in Wales can be ideal for Wasabi, especially in sheltered valleys.

Protection from Elements

Wasabi plants need to be protected from strong winds and frost.
Consider using protective structures like greenhouses or shade cloth to create a controlled environment.

Examples of Successful Wasabi Cultivation in the UK

There are successful wasabi farms established in the UK, such as The Culinary Herb Company, where we cultivate our Wasabi in East Sussex.

Is Wasabi more expensive than Horseradish?

Cost Comparison: Wasabi vs. Horseradish

Wasabi is generally more expensive than Horseradish for several reasons:

Cultivation Requirements: True Wasabi (Wasabia japonica) is difficult to grow as it requires specific conditions, such as a cool, humid climate and clean running water. It's typically grown in Japan and sometimes in select regions outside of Japan that can mimic these conditions.

Harvesting Time: Wasabi takes about 1 to 2 years to reach maturity for harvesting, which is longer than many common crops, including horseradish.

Scarcity: Genuine Wasabi is relatively scarce, and because of its growing demand and the difficulty in cultivation, it remains a premium product.

Substitutes: Much of the "wasabi" served outside Japan is actually a mixture of horseradish, mustard, starch, and green food colouring. This is because real Wasabi is expensive and loses its flavour quickly after being grated.

On the other hand, Horseradish:

Growing Conditions: Horseradish (Armoracia rusticana) is easier to grow and can thrive in a variety of climates and soil types.

Yield and Growth Cycle: It has a shorter growth cycle and can be harvested annually, leading to a higher yield and more consistent supply.

Availability: Horseradish is more widely available and is cultivated in many parts of the world, making it less expensive.

In conclusion, due to its cultivation challenges, longer growth cycles, and scarcity, how much Wasabi is indeed more expensive than horseradish?

What is "English Wasabi"?

Wasabi is cultivated in England.

A locally grown wasabi in England is right here at The Culinary Herb Company in East Sussex!