Pile 'em high: Lateral thinking is essential if you want to be an urban gardener

Potatoes in plastic bags, trees in pots and beets on the balcony...

We're walking down Doughty Mews in Bloomsbury, central London, enjoying the golden sunshine of a spring afternoon. I'm here escorting a group of keen gardeners from the School of Life, a new institution offering adult-education events with a twist. The group are on an "Urban Garden Holiday" – a one-day romp through London's green spaces – and I want them to admire the wild species tulip meadow planted by the gardeners of St George the Martyr school.

Urban gardening certainly has its own special set of problems and tactics. More and more urban gardeners want to grow fruit and veg, and there's much discussion during the day about which crops do best in confined spaces and containers. Cherry tomatoes are generally agreed to thrive even where there's shade some of the day. Many of us have had success growing potatoes in sacks, pots, and even, in one case, plastic bags. And one of our number adds ruby chard to the list, which did well on his 10th-floor balcony, perhaps encouraged by a spectacular view taking in Big Ben and Westminster Cathedral.

We also discuss ways to get round those dreaded allotment shortlists – two people in the group have simply gone "out of borough", putting their name down with an outer London council. They make the 25-minute journey to Barnet, then spend the whole day at their plot. It's not terribly local food, but it means they get to spend time at the weekend in the fresh air and return with home-grown produce.

For me, though, urban gardening always means making the most of every square metre. As we walk through Bloomsbury's alleys, admiring roof gardens and basement courtyards, the group learns pretty quickly that in small spaces, everything must pull its weight. The best urban gardeners are masters of sleight of hand, replacing container planting repeatedly during the year, centring their garden on what looks good, and sometimes even literally using mirrors to distract attention away from what doesn't.

I reckon there is no better way to learn than to take a digital camera and get out and walk the pavements, taking notes and snapping the best and worst you see. Learn from the experts and take advantage of the urban climate: we saw philodendrons, spider plants and bush-sized antirrhinums flourishing, even after our snowy February. It's all testament to the notion that, here, if you really want to grow it, you can always have a go. We even saw a potted monkey-puzzle tree. A bit of extra care to give your dream plant a fighting chance, and there you are: now your only problem is working out how to take it all with you when you move.

The School of Life's Urban Gardening Holiday runs this year on 19 September. For details: www.theschooloflife.com

Home truths: Tips for small spaces

Follow the sun

You want sunlight, but you also want privacy. So plan your garden's fencing only after spending time watching where the sun rises and sets, and thinking about how to make the most of every last bit.

All white now

Coat your exterior wall in white paint to lift the feeling of your space. Couple this with white flowers such as jasmine, pale geraniums and foxgloves (pictured above) for a classy and calming scheme.

Ups and downs

Make the most of the space you have by going upwards or downwards. Trailing plants make the most of blank brickwork below your windowsills; climbers take your garden up into three dimensions.