A moist, velvety brown layer of fallen birch leaves and pine needles covers the ground, emitting a robust scent of muddy dampness. My two companions, Miles and Fergus, are leaping up and down with excitement, like gold prospectors who have struck lucky, yet I see nothing else on that dank carpet, save the odd rotting branch. Miles stoops down, clasps his fingers around an as yet invisible stem, pulls upwards and, from out of the uniform brown background, a perfect chanterelle appears: its spreading umbrella the exact brown of the leaf mould, its stem, now visible, a brilliant yellow. I turn my eyes back to the ground and, as if by magic, I can now distinguish hundreds of the wild mushrooms. Within 10 minutes we have picked three large boxes full of the meltingly velvety fungi, a delicious treat ideally served simply on toast, tossed in garlic and melted butter.

These chanterelles are destined, however, for higher things than toast: within a day or two of being picked they will be served in a wild mushroom omelette at Jamie Oliver's restaurant Fifteen, sauteed with partridge at the Wells Tavern in north London or pickled and served in salad with walnuts and beetroot at the White Horse Inn at Bridge. On the Ivy's menu this month you might even find ivy toadflax salad.

Miles Irving and Fergus Drennan are professional foragers, spending up to 40 hours a week scrambling through woodland, creeping along hedgerows or picking their way across shingle beaches, gathering an enormous variety of wild food from the English countryside. Some items, like chestnuts and blackberries, are obvious, known to us all and plucked by hardy autumn ramblers. Others are less well known, or harder to spot: alexanders, a cross between parsley and celery which grows by the ton around the byways of southern England, was introduced by the Romans; sea beet, dark green, robust, spinach-like leaves; wild chervil, the perfect accompaniment to salmon; sea purslane, delicate, salty, succulent pods that explode on the tongue; and of course no end of chanterelles, morels, ceps and other wild fungi that inhabit our meadows and woods.

'When people talk about exotic flavours, they tend to think of spicy food from the Far East, or South America,' says Ben Walton, Les Routier's most promising young chef of the year, at the White Horse Inn. 'But in this country we have so much on our doorstep, full of flavour, that is, sadly, ignored. The wild mushrooms that Forager bring me are the best I have ever tasted - not just because they are so fresh, but because they grow in their natural habitat, not force-fed in an artificial atmosphere.'

Fergus and Miles are delightfully grungy and hugely enthusiastic about what they are doing, virtually to the point that Fergus tries to survive on foraged food all year round, avoiding seasonings, sugar and wheat, making flour out of ground chestnuts, and, although a vegetarian, occasionally feasting on road kill. 'We tried to make badger sausages once, which were very uriney-tasting and unsuccessful. But we've found that if badger is really fresh and is soaked in milk then it's nowhere near as gamey and strong. I made a badger burger for a rather straight friend of mine - I gave him 100 guesses and he still couldn't tell what it was. Squirrel and seagull are two of the tastiest wild meats to eat though,' says Fergus, a trained chef and an amateur forager for over a decade before he turned 'professional' last year. 'I only eat road kill because the animal was free, not reared in captivity, and not killed for food - which is a principle I was taught by a Buddhist priest when I lived in a temple in China. I only use road kill that is freshly dead - still warm, with eyes still bright.'

The pair, who call themselves simply Forager, are almost evangelical in their desire to make people aware of the wealth of food to be found growing wild. 'In the rest of Europe, foraging is a common, almost everyday pastime,' says Miles Irving, who describes himself as 'psychology graduate, carpenter and musician'. 'In Scandinavia, everyone goes out collecting wild cranberries in the autumn and in France collecting wild leaves like dandelion and chervil for tasty salads is so commonplace no one bats an eyelid. But here, foraging is considered highly unusual, possibly for historic reasons, when the countryside became out of bounds after the Enclosure Acts.'

As food prices soared during the 18th and 19th centuries, landowners enclosed land that had either been waste ground or common land, to turn it into farmland. Between 1750 and 1850, more than six million acres of land were 'privatised' in this way, by more than 4,000 private Acts of Parliament. The accompanying industrial revolution turned Britain's population into a predominantly urban, rather than rural one, and our links to the land were severed far earlier than in other European countries.

'Now we English are a bit squeamish about anything that's too natural,' says Miles. 'We're more scared of a bit of mud than of pesticides; we just want something that is hygienically packaged and rinsed in sterilising solution.' Miles and Fergus want to re-introduce people to this 'relish of wild food' and this year are starting tours of local natural greengrocers, followed by a meal prepared with their finds.

The pair started up in business together at the Goods Shed in Canterbury, a local market with a now famous restaurant of its own, where they still sell their produce on a stall. 'When the Goods Shed opened in 2003, I thought it would be a great idea to sell wild mushrooms there,' says Fergus, 34, who has eaten foraged food for the past 15 years. 'I wasn't too happy when this scruffy looking fellow with a ponytail came in with exactly the same idea.' Fortunately the two shared the same passion for wild food and decided to cooperate. Their first customer was the then chef at the Goods Shed, Blaise Vasseur, who now cooks at the hugely popular gastropub, the George and Dragon at Speldhurst in Kent.

'He asked us if we could find some wild garlic, to make soup with, and it sort of snowballed from there,' says Miles, 37. 'We pooled our knowledge, which even then was considerable. Fergus was already like an old man of the woods and I had always been a keen forager. One of my happiest memories from childhood is picking wild mushrooms with my grandfather, and making and tasting my first nettle soup with him.' Now the Goods Shed restaurant buys much of their pickings, and features their home-made wild cherry and elderflower on its drinks list.

'At the George and Dragon we try to use produce that has come from as limited a geographical area as possible,' says Blaise Vasseur. 'You can't get more local for us than the Kentish woodland. The exciting thing about wild British food is that it is stunningly delicious, particularly the woodland and coastal herbs, mushrooms and nuts. My favourite herb at the moment is the crisp, salty sea purslane, which we cook with creamy, soft scallops. It's a match made in heaven. The wood sorrel with our seared local wood pigeon breast is also a fine combination.'

Forager makes a point of asking permission from landowners and farmers before they start rummaging through hedgerows on private land, even though what they take is unwanted by the farmers, and probably considered to be a weed. 'The law about what you can take from common and public land, such as the seashore or footpaths and bridleways is a fairly grey area,' says Miles. 'A general rule is to only pick the leaves, stems and fruits of plants, never dig or pull them up unless they are in such abundance that they can stand it, and never take rare or protected species. But the beauty of most edible plants – nettles, dandelions, alexanders, fat hen, sorrel – is that they are so prolific they are considered a nuisance. We see ourselves as stewards of the land, taking our lead from indigenous peoples' practices, which focus on sustainability. There are whole mangrove swamps in Australia that only exist because Aboriginal peoples nurtured them. We want to start picking sea-kale, but English stocks were decimated by the Victorians and have never recovered, so if we do take any we will propagate it and re-plant. We see people returning to small-scale farming, but we aren't agriculturalists, we're going further back - to hunter-gathering really.' They are also hoping to expand the business, and plan to offer work to people with long-term mental health difficulties.

It takes determination to go out in all weathers to get cold, wet and muddy, for the sake of sometimes only a handful of saleable produce. As a result, Forager charges fairly hefty prices for its wares: a flat rate of £15 per kilogram box, whether it be full of grey field blewit mushrooms, or a spicy and piquant selection of wood sorrel, wild chervil and dandelion leaves. For the chefs, it can be a learning curve, too. 'Sometimes you end up scratching your head and wondering what you can do with the stuff, if it's a little too artisan,' says Arthur Potts, head chef at Fifteen, Jamie Oliver's Shoreditch restaurant. 'But we always find a use for everything, which is part of the challenge of cooking with the most natural ingredients.' The restaurant uses Forager's elderflower cordial in its champagne and elderflower jelly palate cleanser, and whatever mushrooms Miles and Fergus bring in. 'Part of what Fifteen is about is training up young British chefs to appreciate modern European, and particularly British food,' says Potts. 'And although it's great for them to cook with something from a street market in Milan, it's even better to present them with a British wild puffball with the earth still on it.'

Unlike other purveyors of unusual food who, once they find they are onto a winner suddenly they have a dozen imitators, Miles and Fergus do not have many competitors willing to get their fingernails caked in mud and their faces scratched with brambles. Indeed their greatest competitors are woodland animals after the same stuff. 'We collected more than 60 kilos of sweet chestnuts in the autumn and stored them in nets underground to keep them fresh,' says Fergus. 'If the squirrels find them before we dig them up, they're going to have one hell of a party.'

If it's April, it's time for hogweed shoots...

What to pick in:

January

Frost softened rosehips
Bittercress
Judas ear fungus
Dandelion leaves
Pine needles

February

Dandelion leaves
Wild chervil
Chickweed
Primroses
Alexanders
Wood sorrel

March

Wild garlic
Garlic mustard
Sea kale
Sea beet
Watercress
Fat hen
Morels
Lime leaves

April

Nettles
Hogweed shoots
Hop shoots
Dandelions
Chickweed
Hawthorn leaves

May

Elderflower
Wild fennel
Sea lettuce

June

Lime flowers
Marsh samphire
Sea purslane
Sea beet
Sea lettuce

July

Marsh samphire
Rock samphire
Green walnuts
Camomile
Blackberries
Ceps
Chanterelles

August

Rock samphire
Marsh samphire
Blackberries
Wild cherries
Camomile
Apples
Sorrell

September

Nettles
Rowanberries
Elderberries
Mushrooms galore

October

Apples
Nettles
Rowanberries
Chequerberries
Hawberries
Sloes
Chestnuts
Walnuts
Cob
Nuts
Mushrooms

November

Chestnuts
Mushrooms
Pine needles

December

Pine needles
Sea beet
Sea purslane
Mushrooms
Judas ear fungus

· Forager produce is available at the Goods Shed market and restaurant, Canterbury, 01227 459153, (daily except Mondays). Contact www.forager.org.uk. For more foraging information see www.countrylovers.co.uk The George and Dragon, Speldhurst, Kent, 01892 863125; the White Horse Inn, Bridge, Kent, 01227 830210