Sweet dreams

Once seen as an exotic curiosity, the sweet potato is now being grown in deepest Sussex. Michael Bateman meets the man responsible.

Only the most foolhardy of farmers, you would imagine, would plant tropical crops outdoors in Britain. The sweet potato, for example, needs the warmth of Latin America, Louisiana or southern Spain - not the chill winds of our climate. Chillies, likewise, look to the blazing sun of Mexico and similar latitudes to thrive. But Peter Barford, who has grown both outdoors in West Sussex, is not foolhardy. He has merely decided to push the boundaries of credibility to their limit.

Only the most foolhardy of farmers, you would imagine, would plant tropical crops outdoors in Britain. The sweet potato, for example, needs the warmth of Latin America, Louisiana or southern Spain - not the chill winds of our climate. Chillies, likewise, look to the blazing sun of Mexico and similar latitudes to thrive. But Peter Barford, who has grown both outdoors in West Sussex, is not foolhardy. He has merely decided to push the boundaries of credibility to their limit.

As far as his green chillies are concerned, that might be overstating his achievement, because these crops have been grown commercially under glass in the UK for some years now. But his British-grown sweet potatoes are a remarkable agricultural achievement, and this month they go on sale for the first time.

Many people may find that hard to credit. People don't always believe in Barford's chillies. A BBC reporter visiting him recently, looked at the fields of habañeros, fresnos and jalapeños and said: "There's no way they'll be as hot as the real thing." He plucked a chilli from its bush and bit. "I thought I was going to have to take him to hospital," Barford says. "He was yelling, 'Give me water!' Actually, water's the worst thing to moderate the heat. You need to chew bread. Mexicans always carry a bit in case they bite on a very hot one." Barford's own chillis have the kick of a Mexican mule, registering between seven and nine (out of 10) on the standard chilli heat scale.

In supermarket parlance, chillies and sweet potatoes fall into the "exotics" category. They command premium prices because they are imported from the tropics. This gives Barford room to compete. It's not easy, but at the age of 50 he knows most of the tricks of the trade.

He started farming back in 1975, growing the first courgettes for supermarkets. In those days, they were called - as they still are in America - zucchini and considered exotic newcomers. Since then he has pioneered other crops, including sweetcorn (not to be confused with its close relation, maize, which is much more easily grown).

Barford not only has fields of monster pumpkins ripening for Hallowe'en, but also a glorious carnival of the pumpkin's cousins, butternut, acorn and hubbard squash, another exotic market that is growing quickly. But the sweet potato, Barford believes, will be the next big thing. It is already fiercely fashionable in restaurants steered by fusion chefs such as Peter Gordon, who runs Bali Sugar. It is used as a purée or mash, as a colourful addition to savoury dishes, or as a baked dessert in its own right.

Not only is it good to eat, but in a culinary culture moving more towards healthy food, it has impeccable credentials: low in sodium, almost fat-free, zero cholesterol and high in fibre. As the orange flesh suggests, it is bursting with beta-carotene (vitamin A), containing 25 times as much as broccoli, weight for weight. It is also a source of vitamin E (good news as vitamin E is most commonly found in foods which are high in fat - nuts, avocados and vegetable oils). Indeed, the sweet potato might have been invented for today's health-obsessed society. This is an aspect which has appealed to Sainsbury's, who have leapt at the chance to buy the whole of Barford's first crop.

The Japanese have been on to this for a long time. They have published studies suggesting the sweet potato contributes to Japan's low level of heart disease. Each year they import 40,000 tons from Mexico and 80,000 tons from New Zealand, where it is known as kumera.

The New Zealand name betrays the tuber's origins. The sweet potato can be traced back 10,000 years to Peru where it was known in the ancient dialect as kumar. The food historian Alan Davidson speculates that it travelled west across the Pacific by the route that Thor Heyerdahl followed on his Kon Tiki expedition.

But under its hispanic name, batata, it travelled east around the world, lending its name, confusingly, to the potato. Today it is the most important tropical root crop, a major food item in the Caribbean and Africa, as well as in China and North America. Even in Britain few of us really consider it exotic any more.

They certainly don't in Louisiana, where Barford first asked to buy sweet potatoes from a farmer. He could hardly believe his ears when the farmer asked him: "Why? You got niggers to feed over there?" Shocking as it was, the exchange was a reminder that the sweet potato was a staple crop on the slave plantations, being such an easy plant to grow (it belongs to the morning glory family) and abundant, with a yield of half a dozen or more half-pound tubers per plant.

But how does Barford manage to grow them in Britain? The answer is that he inhabits a unique micro-climate opposite the Isle of Wight, where the Downs part the incoming, south-westerly clouds, creating intense, bright light and long hours of sunshine. To the north, the South Downs block the cold north winds. The Gulf stream keeps the air warm enough to banish frost. Add to this a high water table and a sandy, loamy soil, and you have perhaps the best growing conditions in the UK.

As a boy, Barford remembers it as prime strawberry country. But after he had knocked around the world (he toughened himself as a jackaroo in Australia) he came back with more ambitious plans. Having started with 10 acres - growing courgettes for Marks & Spencer - he has expanded to several thousand. He employs state-of-the-art technology: 650 miles of trickle irrigation; biodegradable sheeting to keep the fragile plants warm and weed-free; and satellite surveillance which can monitor not only moisture and fertiliser levels but the presence of pests such as aphids.

By such means can exotics be nursed to maturity in our unlikely climate. But the modern farmer has to do far more than grow the crops. Today's supermarkets demand an uninterrupted, 52-week supply. So Barford doubles up as an importer, maintaining a supply of squash, sweet potatoes, chillies and sweetcorn from all corners of the globe to supplement his own.

I would love to see the price of sweet potatoes come down and the term "exotic" removed. They were in vogue once before in this country, in Tudor times, when Queen Elizabeth, with her famous sweet tooth, enjoyed them candied. The Americans love them for their sweetness. As a traditional feature of Thanksgiving dinner, they are served baked or roast, with brown sugar or maple syrup and cream. Or they are made into a lovely sweet potato pie (see recipe, right), not unlike pumpkin pie. In China and Japan, sweet potatoes are sold like roast chestnuts by street vendors. In the Caribbean, they are cut into pieces and boiled as a vegetable, or peeled, sliced and fried as chips.

Steamed or baked (whole and in their skins), they take some 40 minutes to cook but, magically, they can be microwaved in only four to six minutes. Removed from their skin and mashed, they make a companionable starchy vegetable for beef, lamb, pork, chicken or fish.

Three of the four recipes given here are from Peter Gordon (from The Sugar Club Cookbook, Hodder & Stoughton, £20), who grew up in New Zealand, where kumera was always on the menu; the fourth is a Jane Grigson recipe for sweet potato pie (from Jane Grigson's Vegetable Book, Penguin Books, £7.99).

Molly's lemon roast chicken

Peter Gordon's grandmother's chicken recipe is roast alongside diced sweet potatoes.

Serves 4

1 large free-range or corn-fed chicken

Salt and pepper

150ml/5fl oz best olive oil

1kg/2lb 4oz sweet potatoes

25g/1oz fresh oregano leaves

2 teaspoons fresh rosemany leaves

2 medium-sized juicy lemons

Preheat oven to 220C/425F/Gas 7. Remove the legs from the bird and cut them in two through the knee-joint. Remove the wings and the suprêmes and cut these into two also. (Reserve carcass for stock to use on another occasion.)

Season the joints lightly with salt and freshly ground black pepper and brown in a little oil in a frying pan.

Peel the sweet potatoes and cut them into 2cm (3?4in) dice. Mix with the herbs, a little salt and pepper and half of the oil. Wipe the lemons and cut them in half lengthways, then slice finely. Place the leg joints on top of the potatoes, sprinkle with the lemon pieces and roast for 30 minutes. Add the suprêmes, drizzle the remaining oil on them and cook for a further 30 minutes. The chicken is cooked if the juices run clear when the flesh is pricked.

Peter Gordon's grilled sweet potato

He uses a grid pan rather than a grill usually.

For 6 side portion

3 sweet potatoes, each about 350g/12oz

Salt

Cracked black pepper

Olive oil

Don't peel the potatoes but scrub them gently - the skin keeps the nutrients in. Put them in a deep pot with two tablespoons of salt, cover with cold water and bring to the boil. Cooking should take about 20 minutes; when they are almost done a skewer will just go through the centre. Drain the potatoes and leave to cool. Slice into 1cm (1?3in) thick pieces, brush with a little olive oil, sprinkle with salt and pepper and grill for two minutes on each side.

Peter Gordon's sweet potato bread

This couldn't be simpler. You'll end up with an irresistible orange-coloured bread that's slightly sweet and rich. If you can't get sweet potatoes, use ordinary potatoes or pumpkin: the result will of course differ but will be just as tempting.

For 2x750g/1lb 11oz loaves

500g/18oz sweet potato, peeled and cut into 2cm/3?4in dice

400ml/14fl oz milk

20g/3?4oz fresh yeast (or 3 teaspoons dried yeast), dissolved in 50ml/13?4oz warm water

800g/1lb 12oz strong flour

1 teaspoon sea salt

Put the sweet potato and milk in a pot, put the lid on and bring to the boil. Cook until the potato is done, then remove the lid and boil until the milk has reduced by half. Put the milk and cooked sweet potato into a bowl and allow to cool until lukewarm. Add the yeast dissolved in the water and mix well, then add all the flour and the salt and knead for five minutes. The dough should be moist but not sticky, so if it needs a bit more flour just add some. Leave it in a warm place to double in size - this should take about an hour. When risen, punch the dough down with your fist and divide it into two lumps of equal size. Roll each piece into a long sausage shape and place on baking parchment on a baking tray. Again, leave in a warm place to double in size.

Turn the oven to 180C/350F/Gas 4. Brush the dough with warm water and sprinkle with a little coarse sea salt, then place in the top half of the oven. After 20 minutes test by tapping a loaf on the bottom - it should sound hollow. If it doesn't, cook until it does; this should take no more than another 10 minutes. Remove the bread from the oven and cool on a cake rack.

Jane Grigson's sweet potato pie

This good pudding has a resemblance to pumpkin pie. I think it is best eaten cold, with plenty of whipped cream.

Sweet shortcrust pastry made with 250g/8oz flour

250g/8oz boiled, peeled sweet potato

100g/3-4oz melted butter

100g/3-4oz dark brown sugar

175g/6fl oz single cream

2 large eggs

1?2 teaspoon grated nutmeg

1 teaspoon ground cinnamon

3 tablespoons brandy

Good pinch salt

100-150g/3-5oz shelled walnuts

Line a 23 to 25cm (9 to 10in) tart tin with a removable base with the shortcrust pastry.

Sieve the sweet potato into a basin and beat in the remaining ingredients, in the order given, except for the walnuts. Chop one-third of the walnuts coarsely and add them to the mixture. Pour this into the pastry case and arrange the rest of the walnuts round the edge of the filling.

Bake at 200C/400F/Gas 6 until the filling has risen and set. Test it with a warm metal knife or skewer. When it comes out clean, remove the pie from the oven. Allow 40 to 45 minutes.