Over Farm, near Gloucester, has 800 acres of arable crops. But that's not why 2,500 people go there every week

It smells just like Sainsbury's; the hot sweetness of freshly baked bread punches you in the nose as you go in, but there all comparisons with a supermarket end. Home-made strawberry flans and crusty loaves, baked on the premises, are the latest addition to the goodies for sale at Over Farm Market. The customers said they wanted them, and their baskets tell a similar story. Happy customers are regular customers, and what farmer and shopkeeper Robert Keene wants - and needs - most of all is to keep them coming all year round.

There are plenty of regulars among the 2,500 people who shop at Over Farm every week, but there is also an enviable volume of passing trade at this time of year, brought in by a gigantic strawberry-shaped balloon. It floats mouth-wateringly above the A40, a couple of miles from Gloucester. The characterful old building that houses the shop once offered stabling and accommodation to travellers, but had fallen into ruin when Mr Keene, the third generation of his family to tenant Over Farm, spotted its potential. Leaving his parents to manage 680 acres of arable, he took over the remaining 120 acres to grow vegetables to sell in the shop.

From small beginnings - just potatoes and onions in season - a prosperous little business has flourished. The retail side of the farm now accounts for 50 per cent of total turnover. There is one idealistic school of thought which holds that a farm shop should sell only what the farm produces (which means employing people on a seasonal basis and having some quiet months during which your customers forget you exist).

And there is the other school, which believes in supplying all the fruit and veg the modern housekeeper wants all year round, aims to be competitive with the local greengrocer or supermarket, and sells its own produce as cheaply as possible. Mr Keene belongs to the latter, but he quickly realised that price differential alone was not enough to draw customers. "These days, people want a recreational experience, not a shopping chore," he says.

Indeed, you do not have to buy anything at all at Over Farm Market. You can sit in the car and have a nap while the children run off to wander through fields of pumpkin, to feed the three Vietnamese pot-bellied pigs, to tickle the goats, talk to the water buffalo (who adores the attention), or perhaps get their buttons nibbled by the ostriches. (Mr Keene bought a pair of ostriches to breed for their meat. Apparently, it tastes like beef but is lower in cholesterol than chicken. However, since Mrs Ostrich is refusing to lay an egg, he has had to make do with their novelty value.)

You would be a fool not to get out of the car, though. Mr Keene's vegetable repertoire includes asparagus, broad beans, runner beans, sweet corn, pumpkins and squash, beetroot, courgettes, marrows, celeriac, cabbage, calabrese, cauliflower, swedes, parsnips, carrots and brussels sprouts on the stalk. Mr Keene experimented with organic produce but, after selling eight times as many inorganic Bramley apples (melon-sized and shiny) as organic (small and slightly blemished), he packed it in.

There are 50 acres growing various sorts of spuds and four acres devoted to strawberries. This week it is the Honeyoye strawberry - very tasty and a deep red; later on there will be five different varieties which will stretch the season to the end of July. You can also buy postcards of the animals, local ice-cream, free-range goose, duck and hens' eggs, and local honey.

The shop's rustic, home-grown appeal is enhanced by ancient farm implements nailed on the whitewashed walls; outside, hanging baskets froth cheerfully and herbs and bedding plants are arranged on old farm trailers. Everywhere, smiling staff wear yellow sweatshirts saying "I'm So-and-so from Over Farm Market". Mr Keene encourages customers' interest with a quarterly newsletter. Perhaps it is not surprising that "grey power" - those who can afford the time and money to shop for pleasure - are the majority of customers.

Mr Keene estimates that produce sold in farm shops amounts to less than 10 per cent of produce sold nationwide, a mere spit in the supermarket ocean. Whether that percentage is shrinking or growing is impossible to chart, since the idea of what constitutes a farm shop is rather vague. Nevertheless, you need look no further than your own car window to notice that the heyday of pick-your-own is gone. These days, it seems, people cannot be bothered to pick and freeze 15lb of strawberries when they can buy imported ones all year round.

This year, however, many farmers have reported an astonishingly successful asparagus season with demand far exceeding supply. There has been a sudden burst of enthusiasm, too, for picking your own squashes - gigantic pumpkins, patti pans, butternut and spigot squashes (the one area in which the supermarkets have done farm shops a favour by whetting the appetite of customers for a new taste).

According to the Farm Retail Association, there are as many farmers dropping out of retailing their crops as there are enthusiasts starting up, fired by the need to diversify. The ones that are doing well enough to expand, such as Over Farm, are run on a larger scale and offer an additional attraction to compete with the multiple retailers.

For farmers to turn retailers successfully, however, they need to welcome the public on to their farms and to treat them as customers, not trespassers. It is not an easy transition. "Sometimes I go to the shop and find myself collared by a customer or drawn into the nitty-gritty of running the shop, and I feel frustrated because I should be planting this or that crop," says Mr Keene.

"My main reason for being a farmer is to grow things. I like talking to people if I've got time, I get a buzz out of watching customers really enjoy themselves, and I feel good about selling what I grow."

Indeed, Mr Keene believes that if farmers only grew what they thought they could sell, rather than spending months working out which crops could earn them the biggest subsidies, everyone would be happier. "In their heart of hearts, most farmers don't feel good about growing crops for the subsidy," he says.

Growing fruit and vegetables may not be quite such a tie as a milking herd, but it is extremely hard work. Over Farm Market is open seven days a week, so Mr Keene is always on call, if not on duty. And, like any other farmer, the weather is rarely what he wants. Still, there is always something fresh for supper, even if it is plain potatoes. And there is always the chance that Mrs Ostrich might be persuaded to lay the golden egg.

'Harvest Times', a guide to farm shops nationwide and PYO farms is available from: Harvest Times, PO Box 200, Winchester, S023 BXJ. Please send 50p in stamps to cover postage.