The freshness of its produce has helped The Wasabi Company establish a considerable reputation, with its exports now going to seven European countries.

At the company’s farm near the village of Micheldever, you will find lush dark green wasabi leaves spread out under protective black netting.

Groundwater pumped from 40 metres below flows like a stream underfoot, and thick gravel of different shapes and sizes replicates the natural streams where wasabi, known by the scientific name Eutrema japonicum, grows in Japan.

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It has been challenging to perfect the environment, but the company uses former watercress farms, which have similar conditions.

A former watercress farmer, Old was inspired to become the first commercial grower of wasabi in Britain.

In 2010, one of Old’s regular watercress customers, a South African chef, approached him about the possibility of growing wasabi, and the rest is history.

Old now runs three different wasabi farms in the south of England with his son, Guthrie, 20, who helped him until late August.

Before 2010, Old had only heard of wasabi as an ingredient for sushi.

When he discovered that it needed the same conditions as watercress – which uses moving water to provide a steady supply of fresh minerals – he decided to try it.

Although he obtained his first batch of 20,000 wasabi plants from a farmer in Japan’s Yamanashi prefecture, his initial attempts at cultivation on his Dorset farm ended with half the crop dying.

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But a trip to Japan’s Shizuoka prefecture to learn from experienced wasabi farmers – initially met with some hesitation from growers – proved invaluable.

Armed with new expertise, Old returned to Britain and began to apply it to his own wasabi plants, typically harvested after 18 months to two years, when the rhizomes grow to around 2cm to 3cm thick and 10cm long.

Old started marketing his wasabi to restaurants in 2012, and initially encountered resistance from chefs who were sceptical of wasabi grown in Britain. Japanese restaurants preferred to import Japanese imported produce. Few were willing to take a chance on the fledgling Wasabi Company.

It was only after he invited the chefs to his wasabi farms, to see how it was being grown and to taste some freshly picked samples for themselves, that he gained a reputation for quality.

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When demonstrating the quality of their produce to visitors, Old and Guthrie often take a freshly harvested wasabi rhizome and scrape the outer layer with a knife, releasing its pungent aroma, Guthrie said. When visitors taste it, they experience an immediate burst of spiciness followed by a subtle hint of sweetness.

“The most interesting thing I find about wasabi is that if you taste it right after grating, it doesn’t have much flavour,” Guthrie said. “But after five minutes, all the heat comes out – and then after 15 to 20 minutes, it loses its flavour again.”

The Wasabi Company not only enjoys the high regard of chefs across Britain, but also supplies Japanese and Western restaurants in the Netherlands, France and Sweden, among other countries.

For Guthrie, who joined his father in the business two years ago, working his way up through The Wasabi Company’s ranks was a welcome challenge, allowing him to learn about the business.

“I started pretty much packing boxes for a year and then slowly worked my way up,” Guthrie said. “It’s been great just learning about something new and challenging myself. But growing wasabi in the UK was always going to be the perfect challenge.”

The company has a wide range of products on its website, from wasabi vodka and mayonnaise to grow-your-own wasabi kits. The wasabi rhizomes cost £10 (US$12.30) for 50 grams (1.8oz).

“More than anything, I’m really grateful to Japan for giving us these wonderful ingredients, which have also opened up the European market,” Old said.