From beets and figs to violet-hued potatoes and cauliflowers...

Why do children so prize the purple one when they squabble over sweets? It's not an obvious choice; the colour of pomp and ceremony is a grown-up and formal hue, rarely cited as anyone's favourite colour and hardly a staple of the average wardrobe or home-decor palette.

Yet children are instinctive; perhaps they make a link at an early age between the flamboyant colour of regal robes and indulgence. Or maybe they just know inherently what scientists have only recently discovered – that foods which are naturally purple are very good for you. Blueberries have long been touted as a superfood, but now it's been found that resveratrol, a property of purple grapes and their juice, inhibits the growth of cancer cells, while the phenols in plums actually kill them.

Purple figs, revered by the ancients, are packed with potassium, magnesium and calcium – the Japanese use them to reduce high blood pressure – while purple varieties of the cabbage family have been shown to promote healthy brains and hearts and help burn fat.

But it's more likely that it's the sheer fecund beauty of the produce that exudes a primitive allure as summer segues into the season of mellow fruitfulness and those of us within reach of a bramble bush prick our fingers foraging for blackberries. Nothing symbolises autumn more than Victoria plums with their purple-blue bloom, aubergines shining deep violet and pale lilac and fat, sweet purple figs and grapes languishing sumptuously among their chaste green cousins.

This year, the selection of flamboyantly-shaded autumn veg is no longer limited to what we expect. Increasingly, we are being confronted with purple potatoes, asparagus, mangetout, carrots, tomatoes and sprouts, as the greengrocery section attempts to dazzle us with relentless novelty.

Supermarkets are pushing the power of purple to almost exhausting levels, with our cheerful complicity. Purple cauliflowers flew off the shelves at Tesco in the few weeks they were around, sales of purple grapes have doubled year on year at Sainsburys, while Marks & Spencer, whose fat Bursa figs are being sold in growing numbers despite the eye-watering price of £1.15 a pack, has also seen 48 per cent growth in aubergines.

"Our customer understands that purple equals healthy – the good news about blueberries and red wine have given them that message," believes M&S agronomist Simon Coupe, offering a reason for the surge in growth of these dark beauties. "Television chefs have made aubergines more accessible, and we did so well with purple mangetout during their short three-week season that we are planting a lot more for next year." But athough he thinks there's a place for purple asparagus, Coupe has his doubts about carrots of the royal hue: "They eat well raw, but turn quite grey when you cook them".

This might be why the carrot, originally purple when found in Iran and Afghanistan, was bred to a more familiar and appetising orange by the Dutch four centuries ago, according to Charles Spence, professor of experimental psychology at Oxford University. But now we are turning the clock back, he says: "More and more companies are playing with novel colours in both food and drink to catch people's attention."

Is all this tinkering with nature justified? The purple-pink cauli at Tesco was part of a rainbow pack that also included emerald green and vivid orange, as well as the usual white. Tesco vegetable buyer Jeni Gray considers the painted-looking veg "works of art" and praises them for their wow factor at a time when cauliflower was seen to be losing out in popularity to broccoli.

No one has a bad word to say about purple sprouting broccoli – MasterChef veg expert Greg Wallace believes it is vastly superior to green broccoli – and now purple Brussels sprouts are exciting buyers at Asda, which introduced them last year. Waitrose was sufficiently impressed by the bizarre-looking little brassicas to organise their own supply for this winter.

The food developers have been driven to purple prose in praise of their violet variations on a theme. Sainsburys claim aphrodisiac qualities for their Purple Passion asparagus, which keeps its colour when cooked and can also be eaten raw, recommending its "libido-boosting" qualities for a romantic meal at home.

Inspired, perhaps, by healthy sales of figs and grapes of the colour, Sainsburys will this month relaunch the Purple Majesty potatoes that sold at the store much better than expected last year. In the first week alone, sales were phenomenal, says buyer Julien Roberts: "Their magical colour has captured the imagination of the whole nation," he raves. The potatoes are grown by Albert Bartlett at the company's three UK locations. The company's head of development, Gillian Kynoch, points out that purple potatoes are not as much of a novelty as we might think: "Purple is a common colour among traditional potato varieties – the reason we consider white the norm is because they're the ones Raleigh chose to bring to Europe," she says.

S Walter could just as easily have brought home the purple, which remain a common sight in the markets of South America, but Bartlett's are not alone in raising violet spuds on British soil. Black Truffle are grown in Kent, Shetland Black further north. But Wallace, who is a greengrocer as well as a Masterchef judge, positively detests purple spuds. "Potatoes are essentially a comfort food, there to mop up other flavours, and I am against anything which brings them to greater prominence," he rages.

"Purple asparagus is silly, and so is purple cabbage, even though we sell it at the farm in which I have a share. I'm OK with purple carrots – they bring some interest to a salad – but essentially I think dishes should be built around flavour rather than colour."

There is plenty of purple action afoot in professional kitchens, where David Escobar of Cassis has adopted it as a signature colour, down to cocktails made of violet-infused gin and jewel-like blackcurrant sorbet topped with blueberries. But there's much more than a passion for purple to his penchant for Vitelotte potatoes, insists Escobar, who pairs them with mackerel, while sous chef Stefano Dondoli pounds them into astonishingly beautiful lilac gnocchi which sing out from their bed of vivid green basil coulis.

The restaurant also uses lavender – currently perfuming a hollandaise to accompany grilled sea bass, and flavouring post-prandial chocolate truffles. Escobar says: "It's an incredibly versatile herb to cook with, with lemon and citrus notes making it a particularly good accompaniment to fish." An appreciation of its rich colour has also made beetroot a staple on smart restaurant menus; chopped and mixed with hard-boiled egg, it makes a lovely garnish for purple asparagus vinaigrette. The pairing of beetroot and asparagus comes from Chez Panisse, which pioneered the culinary use of lavender in California more than 30 years ago; British chefs are more likely to reach for purple basil or sage on the herb shelf.

A useful side benefit of so many of our five-a-day now being available in a different shade is likely to be a greater uptake by children who can't be tempted to eat their greens. There is a reason for this: "Green vegetables are more likely to be bitter than those of any other colour, and children inherently avoid tastes they perceive as poison," says Professor Spence. It won't be long, if growers have their way, before we are urging our kids to get more of that lovely purple stuff down them – and we won't be talking jelly babies or fruit gums.

HOW CHEFS ARE PLAYING TO OUR PASSION FOR PURPLE

The Ivy's Gary Lee mixes heritage purple carrots with beetroot to make an exquisitely hued salad, pointed up by white feta and a poppy seed and mustard dressing.

Laura Santtini, the restaurateur's daughter who captured umami in a tube, packs a powerful punch with a purple soup of beetroot blitzed with fresh watercress and topped with crème fraîche and lavender gremolata. The recipe is in her new book, Flash Cooking (Quadrille).

Vincent Menager will open The Balcon on Waterloo Place later this month with a plum tart tatin that he calls "the essence of autumn", paired with clotted cream and a pear liqueur sorbet.

The chef at Brighton's Terre à Terre restaurant wraps soft sheep's cheese in beetroot and damson "leather", dressed with purple sprouted seeds and violets and pansies.

Alexis Gauthier, of the eponymous restaurant, mashes deep purple potatoes with olive oil and grain mustard to accompany butter-poached lobster. His purple sprouting broccoli gets a simpler treatment, dressed with aged balsamic vinegar and black truffle.

Brumus at London's Haymarket Hotel has been complementing its purple and pink decor with a dessert of spiced poached plums with blackberry sorbet.

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