If you left the house 10 years ago with a wicker basket to harvest sorrel, ceps or cobnuts, most people would snigger and point you towards the nearest supermarket. Mushrooming? Heaven forbid; the fungi world was fraught with danger. Hedgerow berries were bird food, wild herbs were weeds and anyone who knew where their food came from was an anorak-wearing bore, a die-hard hippie or plain eccentric.

But in recent years, that perception has changed. Television programmes such as Valentine Warner's What to Eat Now and celebrity chefs like Jamie Oliver have enlightened us to the edible delights that can be found on our doorsteps. Today, any chef worth his or her Michelin salt is foraging or sourcing wild food that sings with natural, integral flavours, not least René Redzepi, chef of the two-starred Noma in Copenhagen, crowned World's Best Restaurant for the third time in 2012.

As any expert is quick to point out, foraging is about more than a good meal. Gathering food in the wild immerses us in the elements, sharpens our senses and reconnects us with our surroundings. Where globalisation has, gastronomically speaking, cast us adrift, foraging anchors us in the here and now. There is such a thing as a free lunch after all -- if you are willing to look for it.

London's hunter-gatherers

Think of foraging and what comes to mind? Wild asparagus in France? Meaty mushrooms in a Scandinavian forest? Summer bilberries in the Alps? While urban railway bridges, parks and pavements may not be the first image you see, many cities have been quick to embrace the foraging trend.

In London, a growing number of groups, including Abundance and Hackney Harvest, are promoting free, pick-it-yourself forays, with maps of fruit trees in the area to get you started. North London-based Urban Harvest also organises events, including edible flower walks and the urban harvesting of plums, apples and chestnuts.

For a proper introduction to the art of foraging, consider joining a guided walk or workshop. You will swap the tube for the trail on the one-day Food Safari tour, led by foraging pro Nick Saltmarsh, one-time supplier to famous London restaurant Le Gavroche. In summer you can hope to find cherry plums, elderflower, chickweed, nettles and wild garlic; in autumn, a fruity feast of rosehips, blackberries, crab apples, damsons and hawthorn berries. Besides learning to identify wild food and pick it safely (and legally), you will learn how to turn what you find into appetising fritters, pies, pestos, preserves and jellies. The £150 cost is not cheap, but it includes lunch and you will go home armed with recipes. It is popular, so booking months ahead is highly advisable.

Alternatively, hook onto one of the wonderfully informative Foraging Courses, run by the author of the wild food guide Eatweeds, Robin Harford, who taught at Cornwall’s Eden Project and was featured in BBC Two's Edwardian Farm. Robin's courses in central London and Edinburgh (£85) introduce you to what he calls “nature's wild food larder”, and have an emphasis on sustainable foraging as you comb the city for edible plants, which are later prepared into a light lunch.

If mushrooming is more your scene but you cannot tell your morel from your chanterelle, help is on hand at Fungi to Be With. Andy Overall leads you into the enticingly earthy and outstandingly diverse depths of the mushroom world on walks, forays and workshops in London’s green spaces, including Wimbledon Common, Hampstead Heath and Epping Forest.

North America’s park life

Hopping across the pond brings you to the wilds of New York. True, the much-frequented parks of Manhattan and Brooklyn are not where you would expect to search for your supper -- but passionate naturalist and “Wildman” Steve Brill proves otherwise. For a mere $20, you can join one of his four-hour foraging tours in Manhattan’s Central Park or Brooklyn’s Prospect Park, which he peppers with unwavering enthusiasm, be it for the common dandelion or pungent wild garlic, the chickweed that “tastes like corn-on-the-cob” or the “lemony flavoured sheep sorrel”.

To delve deeper into this mysterious world, visit the urban foraging blog of Ava Chin, who writes with vigour for the New York Times on everything from Fort Greene Park's field garlic to Staten Island's chickweed.

Other places across North America are also in on the trend. San Francisco's wild food community ForageSF is the brains behind the Underground Market and the Wild Kitchen, where sustainably foraged ingredients shine on an eight-course tasting menu. In Los Angeles, Forage brings freshly found produce to the table. Heading north to Vancouver, imaginative chef Robin Kort is the pioneer behind Swallow Tail Tours, which offers Dungeness crab fishing and wild mushroom hunting.

Head down under

As of late, foraging in Australia has gone way beyond the survival skills of finding food in the bush. In Sydney, “scrumpers” search for herbs and berries that thrive in the sunny, coastal climate. Naturalist Diego Bonetto leads foraging excursions in and around the city, including mushrooming jaunts and walks to dig up seasonal treats such as dandelion, chickweed, plantain and sow-thistle.

Melbourne's shining star is the award-winning Attica, where chef Ben Shewry has won the highest accolades for his cool approach to foraging and his winningly fresh and interesting menus. If you would rather hunt for the raw ingredients yourself, browse Edible Weeds for walks and cooking workshops run by local permaculturalist and edible weed enthusiast, Doris Pozzi.

The article 'The art of urban foraging' was published in partnership with Lonely Planet.