The next time you grab a box of to-go sushi on your lunch hour, you might want to check what you're dabbing on your Cali roll. While we've grown accustomed to spreading that lurid green paste across trays of sashimi and tuna, it probably isn't wasabi you've developed a taste for.
Mustard and horseradish are more likely to be playing a part in your heat addiction, because those little tubes of pungent pastes that taste great added to anything from steak to mashed potato don't usually contain any more than 3 or 4 percent wasabi.
Why is fresh wasabi so tricky to get hold of? As one of the hardest plants to grow commercially and fetching up to £250 a kilo, farming this ancient Japanese import isn't for the faint hearted. But it also proved too tempting of a challenge for Jon Old, whose family have grown watercress in the south east of England since 1850.
By repurposing empty Victorian gravel water beds for wasabi, the notorious distant cousin of mustard and horseradish now grows on a commercial scale for the first time in the UK. Although The Wasabi Company's main plot is in Dorset, I've been sent to Hampshire, because the trials taking place at wasabi basecamp have to stay firmly on the down-low.
According to Nick Russell, manager of the wasabi branch of the business and my guide for the morning, the competition is keen to get a look-in from places as far flung as Tasmania. The Wasabi Company must know they're on to something, (there have been code words for discussion of anything wasabi-related over email) but try as I might, Russell won't budge on what on earth they could be experimenting on with an (at least) one thousand year old brassica.
It's no wonder, really. Gram for gram, wasabi is considered the most expensive vegetable in the world, and it takes a whole 24 months to mature. I don't even know if I'd show me around.
Like Chattanooga, Tennessee, parts of south east England form a perfect climatic analogue to the Izu Peninsula in Japan, where wasabi was originally cultivated. A few minute's drive from a one-train-village and Russell and I are stood in a small, unassuming field somewhere in Hampshire. It's raining almost non-stop and for the first time in weeks, it's actually cold. He tells me it's a perfect day for the wasabi rhizomes. Of course it is.
"What we're trying to recreate is wasabi's natural growing environment, which is the mountain streams of Japan, and in those areas they've got these huge trees which overhang all the streams and provide a lot of shade," Russell explains. "That's one of the main things that the plant needs. They don't like sunlight and an English summer is stereotypically not that great, so the wasabi is pretty happy with that."
Under gauze specially created to generate 80 percent shade, we step into a cool tent, standing on what appear to be stone foundations, but are actually the converted watercress beds. Wasabi's ideal conditions are often referred to as a "Goldilocks climate:" not too hot, not too cold, and with access to spring water that doesn't vary too much in temperature from season to season. In Hampshire, some 500-litres-a-minute of calcium-rich fresh spring water runs through the beds, making it a pretty peachy growing environment for wasabi to take root.
"We're lucky enough to have natural spring water which is just bubbling straight out of the ground," says Russell. "It's around ten to 12 degrees, but because it is coming from so deep down, the water just stays at that temperature. The plants don't actually like sitting in water, they just need a fresh supply, and it's also rich with minerals that can only aid the growth."
With the Victorian beds well established, daily spring water flowing through, and night and shade to keep the plants cool even in the height of summer, I ask Russell if it's really all that hard to grow.
"It's described as one of the hardest things to grow commercially," he maintains. "It takes 2 years from planting to harvest and for that whole period, you're open to the potential issues: disease, pheasants coming in and pulling the plants out, the weather … There're so many things that can spoil the crop with that much grow time."
Across those 2 years, the wasabi can grow anywhere up to 300 grams—the smaller ones giving a sweeter flavour while the larger ones developing a nicer, rounded profile. And it's not just the rhizome that's edible, the whole plant is—if you don't mind countering a few bitter roots.
Sitting at a wooden bench, Russell begins to hack away at the rhizome he's pulled from the water bed's gravel, taking away the flimsy-looking stalks to expose the stem. He explains that if you were to just slice away at the rhizome, you wouldn't get any of the flavour.
Instead, Russell pulls out a Post-it note-sized grater used especially for wasabi paste. Working in a circular motion, he breaks down the wasabi to a cellular level, where the plant's enzymes are combined to produce a chemical reaction, which then makes a paste to create that famous heat and flavour.
The full effect doesn't start until about two or three minutes in, and only lasts for about twenty minutes, before totally disappearing. Talk about fleeting.
"This is exactly why you can't have wasabi in a packet," Russell explains, "because you can't recreate this chemical reaction. Grating it forces the enzymes inside the rhizome to combine, which creates all the flavour and taste, but they also create something else called isothiocyanates, or ITCs, and that help break down the response to cancer cells, so it helps slow down the blood supply to cancer cells, so theoretically, it can help combat cancer growth."
Originally known as yama hajikami, or wild ginger, it's no wonder wasabi began as a semi-aquatic herb cultivated for its medicinal uses. As far back as 1600 BCE, wasabi was grown for its antiseptic properties that lent themselves perfectly to a diet high in raw fish, in the same way the hotter climates of India, Malaysia, and Thailand favoured capsicums, garlic, and onion to kill off bacteria.
Asked if he thought fresh wasabi would ever be able to replace the cheaper paste found alongside supermarket sushi, Russell seemed pretty enthusiastic: "15, 20 years ago, no one had any idea what wasabi was in this country. But everyone's dining is becoming a lot more adventurous. Wasabi was once reserved for the higher classes of Japanese society and its now making its way into the average home."
As much as I'm enamoured by the theatrics of creating a paste of enzymes and ITCs from a gnarly looking rhizome, I can't quite imagine carrying about a pocket-sized grater for my lunch. But once I try a piece of the fresh wasabi, the idea of a bright green processed wasabi spread doesn't seem all that appealing anymore. The fresh stuff has a clean, strong, almost revitalising taste, entirely different to the sinus-wincing after-effects of horseradish or mustard.
If we can be convinced to scoff raw fish by the boxful, perhaps fresh wasabi and its accompanying graters and bamboo brushes will become as familiar in the years to come. Lunchtimes would certainly taste a whole lot better for it.