I didn't just return home from Worton Farm Organic Vegetable Garden clutching a box of freshly laid guinea fowl eggs with their glorious creamy yolks. I returned with a wealth of natural images supplied by the birds that inhabit this lovely part of Oxfordshire, too.

During my afternoon at the garden, in a hamlet mid-way between Cassington and Yarnton, I'd watched swallows dart backwards and forwards inspecting a newly established storage shed designed to provide them with safe nesting space. I also saw a buzzard dive towards its prey and caught a fleeting glimpse of a red kite swooping overhead and all just half a mile from the A40, and five miles from Oxford. Had my visit taken place in June, I would have been able to see at least 20 different species of butterflies, too.

I was at the vegetable garden by invitation of head gardener David Blake, from Melbourne, Australia, who, with his wife Anneke, has spent several years turning two-and-a-half acres of rough fields into a thriving organic garden with polytunnels, chicken runs, fruit trees and bee hives. Now that he is satisfied that the garden is beginning take shape, he has decided to open it to the public.

He hopes that visitors will be encouraged by what they see and even come to understand just how effective companion planting can be. He also hopes they will recognise the worth of allowing nettles and particular weeds to flourish in areas where they can attract the bees, insects and predators, which in turn attract the birds.

He wants us all to get a feel for just how the earth responds to kindness. Take the water he uses, for example. As an Australian, he knows the worth of water conservation, which is why it won't be long before he can wave goodbye to the Thames Water system completely, thanks to a 15,000-gallon tank he's installed and further tanks collecting rain water around the garden.

Following Prince Charles's lead, his waste materials and sewage can be treated naturally too, using drains that are filtered through bark, reed and willow beds. This is a garden where nature is given its head, and where insects, birds and even the earthworms do most of the work.

"Did you know that good soil contains at least 20 earthworms per square foot?" David asks, as he riddles his fingers through the brown earth to reveal two wriggling worms. "They help me fertilise the soil by taking everything that falls onto the surface down into the soil, sometimes a metre deep or more. I throw straw onto the earth and the worms take it in, doing my work for me."

Careful rotation of crops, as laid down by the Soil Association, is important too. Brassicas are moved to the plot where runner beans flourished the year before, and root crops such as carrots are moved to the bed in which flowers once grew. This way the soil remains fertile and crops give a far better yield. David accepts that turning his back on chemicals has meant there are seasons when particular crops fail or give a small misshapen crop. But once a carrot is peeled and cut into pieces, the original shape hardly matters.

To ensure good crops of vegetables such as sweetcorn David simply scatters three times as many seeds as necessary; this way the birds can have their share and still leave enough seeds to germinate. Companion planting includes planting loads of nasturtiums among the crops; these attract the pests, leaving the main crop untouched. Obviously this makes for a colourful garden too.

Last year, he added 150 apple trees to the garden, taking great care to chose local varieties such as the Eynsham Dumpling, originally raised by F.W.Wastie from Eynsham in the 1960s, and, of course, the Blenham Orange, dating back to the 18th century.

David is having great fun seeing how many different types of tomatoes he can grow using heritage seeds. His year he's planted about 20, including the Paul Robeson variety. This famous tomato has almost a cult following among seed collectors and tomato connoisseurs as it produces brick-black fruits weighing anything from seven to ten ounces, which boast a remarkable sweet and smoky flavour. They look great too.

'Diversity is important," David remarks, as he opens an old box where he stores his collection of heritage seeds to reveal a mass of little packets, each containing real treasures.

He's convinced that if he can persuade us to stop looking for perfection and accept the virtues of some of the older varieties, that come in such a glorious mix of shapes and sizes, we will be helping the natural world and giving our taste buds a treat at the same time.

As his hens and guinea fowl are able to forage among the trees of a small wood alongside their run, his eggs taste excellent too. There's something particularly good about an egg laid by fowl enjoying such a superb environment.

Apart from opening the garden between April and December from Wednesday to Saturday from 10am to 5pm (or by appointment), David and Anneke sell the Worton Farm produce outside the Eynsham Emporium, in Mill Street, Eynsham, every Saturday from 9am to 1pm, at Wolvercote Farmers' Market, Wolvercote School, on alternate Sundays between 10am and 1pm, and at Woodstock Farmers' Market on the first Saturday of the month from 8.30am to 1pm.