In garden centres in the UK vegetable seeds have begun to out-sell flowers; a hundred thousand people have put their names down for allotments. In Totnes, there is Garden Share; in Todmorden the people compost in the park. In London, there are vegetables on balconies, canal barges, and in skips. On my estate in Hackney in east London, I can see the last tomatoes of the season ripening on at least a dozen balconies. It’s rumoured that DIY chain B&Q is soon to sell pig sties for the back garden.

This month, we opened our exhibition ‘The Good Life’ with a debate which explored the phenomenon – and asked ‘What next?’ Will the momentum continue into 2010?

To Geoff Stokes, national secretary of the Allotment Association, it began two and a half years ago. Until then, his job was to stop councils selling allotments to developers. But the phone calls changed: how do I get an allotment? Can I make an allotment?

It’s about the environment, of course. It is also about physical and mental health. Scientists have produced data to prove what gardeners have always known: digging and weeding cheers you up and keeps you fit. And it’s also about a change in our approach to food. There’s no such thing as a typical allotment holder, but there is no doubt that many newcomers are middle-class female professionals who want to be in control of what’s on their plate. The change in gender is a huge shift.

At the debate I was struck by the importance of community. Alys Fowler showed her project in Birmingham in which strangers met on Facebook and transformed a lawn into a veg patch on a long, muddy, and cheerful summer’s day. Neighbours became friends. (My tip for next year: it will be about community orchards, not allotments.) And ‘grow your own’ is being phrased out for ‘grow it yourself’. You grow, but you share.

Most remarkably, it’s the economy. An upward curve in interest became exponential when Lehman Brothers collapsed. In the USA there is a waiting list for backyard chickens. The last time that happened was in the months before the Millennium. It’s irrational but it’s true: people buy chickens when they are anxious about the future. In a recession we like to have roots, soil, and belonging. As a woman who grows plants on the balcony of a council flat put it: ‘When you have a little bit of earth all your troubles go away.’

At the debate, Alys Fowler sat beside her heroine, Joy Larkcom, whose journeys to Europe in a camper van in the 70s to collect new varieties of vegetables put the crunch and the spice into the British salad bowl. I’m an old Good Lifer too, added Bob Sherman, a soldier who became a food grower and director of operations at Garden Organic. We do seem to be re-living the late 70s. In 1978, waiting lists for allotments increased by over 1,000 per cent. But in the consumer boom of the 80s, the plots were abandoned. Will it last this time? Or will we go back to the supermarkets as soon as the economy picks up?

This time is different, agreed the audience. To grow an element of what you eat has become integral to the modern lifestyle. There is the change in gender balance. Above all, it is the mass recognition of environmental finality. We’re living at one of those moments in history when people know that society must change: like the 1970s, or the 1920s, or the 1880s, when William Morris imagined a new London in News from Nowhere. Trafalgar Square would become an apricot orchard; manure would be piled up in an emptied Houses of Parliament; the corrupt, dark, traffic-choked city would become a community of woods, meadow, and smallholdings. It’s a book to re-read at a time when we know that the modern city must change.

So what are the challenges? Land, first. There are glimmers of hope in the councils handing over their parks. Lambeth council has given our Museum staff an allotment in a local park – and the Mayor’s office has funded Capital Growth: for a grant of £2,000, residents can plant raised beds in the car park of a tower block. But new housing schemes must increase growing spaces. That is yet to happen.

Next, there is knowledge. In a hundred years of urbanised society we’ve lost our ancient connection with the realities of Nature. Cities, and bureaucrats, live in denial of the seasons. What I enjoy, personally, is picking fruit from old, abandoned trees in London. This evening I will pick bucket loads of eating apples from an old tree beside the Olympic Stadium, and on Saturday I will cycle to another favourite in Green Park. But I will be the only person climbing the trees. This August was a great plum harvest in Hackney. I remember picking plums outside a coffee shop in Broadway Market. Not a single person looked up from their copy of the Guardian.

Finally, there is winter ahead: months of drizzle, mud, cold fingers, and aching backs. At bottom, growing food is hard work. At times, it’s a battle. To my mind, the biggest challenge is our own self-indulgence as consumers. Globalised supermarket food is easy and cheap to buy. Too cheap.

What I found most inspiring at our exhibition opening and debate was the personal optimism of the ‘Good Lifers’ who crowded the room to chuckle and share memories of sexing chickens, homespun sweaters, and the blissful exhaustion in front of wooden fires. They remind us of the value of individual action, combined with national campaigns such as Garden Organic. The first step is to climb a tree and pick an apple. Do it yourself.

Christopher Woodward is director of the Garden Museum in London.