Gardens: James WongView larger picture

James Wong in his small plot in south Croydon. Photograph: Nicola Stocken

There’s little chance of anyone coming across James Wong‘s front garden by accident. But if they do, there’s even less chance of them missing it. Down a no-through-road in south Croydon punctuated by well-kept lawns, tidy flowerbeds and clipped hedges, there’s a small plot packed with plants that even the keenest gardener would struggle to recognise. Strictly speaking, it’s not Wong’s garden, it’s his mum’s, but she’s happy to let him do as he likes with it because, “It saves her the bother of mowing the grass.” Wong lives in central London – “to be near the pretentious wine bars” – and comes down to Croydon twice a week to sow, weed and prune his plants. And to eat them: finding new plants to eat is his passion.

Wong, a botanist by training, made a name for himself as the presenter of Grow Your Own Drugs, a TV programme about herbal remedies, and has since appeared on Gardeners’ World and Countryfile, as well as becoming the Gardeners’ Question Time expert on exotics. His philosophy is easily summed up: “Why bother to grow something everyone else is growing when there are so many other untried varieties?” He was brought up in Singapore and Malaysia, and initially experimented with ornamental tropical plants that few realised could be grown in colder climates, but his focus shifted after the Royal Horticultural Society invited him to give a talk on growing berries.

“I started preparing the night before,” he laughs, “and started panicking when I typed ‘growing berries’ into Google and got 400,000 hits. What could I possibly tell an audience of keen berry growers that they didn’t already know? So I started thinking about why so much horticultural training is directed towards the culture of the same 20 edible plants, rather than the 3,000 and more that you can grow. Was there a reason this stuff wasn’t being grown, other than force of habit?

“I lectured about the different berries that could theoretically be grown in this country, and expected the audience to collapse with boredom. Instead, I ended up with two and a half hours of questions, most of which I had no answers to, because there weren’t any to be had at that time.”

Gardens: James Wong Thai basil
Thai basil. Photograph: David Yeo

So began Wong’s transformation of his mum’s front garden into a test lab. Every plant has to prove itself, with only the best deserving inclusion in his book on growing exotics, James Wong’s Homegrown Revolution . Not only must they be easy to grow (he doesn’t have a greenhouse), but they must also produce a decent crop. His Andean potatoes failed at this hurdle, as did his soya beans. “I’d need a whole field to get a worthwhile crop.”

One berry that did pass muster is the raspberry hybrid ‘Glencoe’. “It’s got this amazing fluorescent purple colouring and tastes like a raspberry enhanced with E numbers. Best of all, it doesn’t seem to feature on birds’ colour spectrum.” It turns out that many unconventional plants are easier to grow than more familiar ones. “Most pests recognise a cabbage from a long way off,” Wong says, “but they don’t have a clue what a tomatillo is.”

Pests and me both.

Cucamelons. Photograph: David Yeo

“They’re a bit like a cross between a cape gooseberry and a tomato. They’re used a lot in Mexican food and I’ve only ever seen them in a spice shop in west London for £2 each. I can get a couple of kilos off each plant. Here, try one.” I do. It’s rather good.

Wong talks me through some of his other crops. The Sichuan pepper: “Don’t grow them for the seed pods; grow them for the early spring leaves that are like a Thai green curry paste.” The cucamelon: “Tastes like a cucumber, but is far easier to grow and sells for £12.99 a punnet in posh delis.” Asian pears: “Crisper and more fragrant than European pears.” Hardy kiwi fruit with no fur and twice the sweetness. Pineapple guava, asparagus peas, blood-red sweetcorn, Thai basil… it goes on.

Gardens: sweetcorn 'Ruby Queen'
Sweetcorn ‘Ruby Queen’. Photograph: David Yeo

Is there anything he can’t grow? Wong pauses. “Chillies are tricky, because there’s seldom enough sun to generate enough heat in the plant, but most plants are surprisingly hardy. The reason we don’t grow or eat them is largely cultural. In Asia, hemerocallis [daylily] is grown as food; we grow it as ornamental flowers.” The same goes for dahlias, an unexpected sight in Wong’s garden. “They were brought over here for their roots, which taste like Jerusalem artichokes, but we started to value them for their flowers and forgot about eating them.”

It sounds almost too good to be true: bumper crops of exotic fruit and veg that the well-off fooderati are paying vast sums for. But can Wong be sure his new varieties aren’t going to poison anyone? “That’s not so hard as all that,” he says. “You can check the records of what people have eaten in different parts of the world over the centuries. And, failing that, it’s easy to measure a plant’s toxicity levels. Many plants are toxic if you eat too much of them. Taste is another matter, though. You just have to try it and find out.”

So what plants failed his own taste test? Wong doesn’t pause. “Coriander. Can’t stand the stuff.”