Urban growth: A gardening guru is getting children hooked on the joys of growing fruit and vegetables

Tom Moggach has a way of falling silent in the middle of a sentence, as though he's just remembered something he ought to be doing. When it first happened, I fully expected that he'd excuse himself from our conversation and dash out of his house into north London's busy streets. He has plenty of reasons to do so.

Through the company City Leaf he founded in 2009, he helps schools, community projects, councils and other organisations across London to set up food-growing schemes. He teaches at a local primary school. He writes the gardening column for Jellied Eel, the magazine of the London Food Link. He's heavily involved in Capital Growth, the partnership launched by Boris Johnson and the LFL to provide 2012 new growing spaces in London by the end of the year. Already, 1694 projects are under way: 90 in Tower Hamlets, 100 in Lambeth, 101 in Southwark and a whopping 111 in Camden, Moggach's own borough.

He took me round the corner from his house to look at one of the spaces he helped set up, a small triangle of leftover land at the end of a row of terraced houses in Bassett St. Raised beds built from wood run along the back of the plot. Rows of big dump bags (the kind builders deliver sand in) fill the rest of the space. "It's a mixed community here," explained Tom. "Bangladeshi, Somali, Albanian, east European. This is somewhere everyone can meet, have a common purpose. The actual harvests we get are a perk. It's the process that counts." Anyone in the scheme can take over a dump bag filled with soil and use it as a mini-plot to grow stuff.

By now I was thinking that the mid-term silences happened perhaps because he's so bound up in his subject. He wants to pitch his thoughts accurately. He minds. "Profound experiences take place when you garden," he says. "You get a deep sense of peace, even if you are just pootling about with tomato plants."

Moggach, 36, was born in Camden and lives there still, in a terraced house with hens in the backyard and an old bath, sprouting a fine crop of salad leaves, perched on the flat roof of the back extension. City gardening is what he knows and now he's written a book about it, The Urban Kitchen Gardener (Kyle Books, £16.99).

You can tell by his kitchen, heavily potted and panned, that he loves to cook and that's why his book concentrates on food crops that city gardeners can grow without too much trouble. He covers nine vegetables, 10 herbs, salad leaves, and a few easily grown fruit such as currants, gooseberries and strawberries. His instructions are all geared to the particular conditions that city gardeners face. How much sun does this crop need? Will it grow in a pot? Importantly, he gives the minimum depth of compost you need for each crop in a container: 25cm for peas, 8cm for coriander.

He includes recipes and also a useful "Ways with..." checklist for each entry, a reminder of all the things that you can do, for instance, with fresh peas or redcurrants. For him, cooking came before growing food. For some time, he worked as a dogsbody in the kitchens of various London restaurants, before reading English at Bristol. He travelled through Africa as a rep, selling books, then came back to England to train as a primary-school teacher.

That decision took him by surprise and though he's no longer a full-time classroom teacher (he did it for five years), teaching and training remain at the heart of his work with City Leaf. "Life in a city is busy, hectic. But once you get hooked into gardening, even if only in a small way, you have the means of releasing yourself from the pressures of modern life. I enjoy helping people to do that". There's another reason he likes what he does. City dwellers don't have much need to click into the changing seasons of the year. Growing food connects them back into that calendar.

Further down the road from the community garden is Rhyl Primary School, where Moggach helped turn a corner of the car park into a school garden. Three raised beds were made in the sunniest corner and the school eco-club built a polythene-covered greenhouse against the yard wall. Wednesday is gardening day and every child in the school spends time in the garden with Moggach and his colleague Anna Locke. For the really keen gardeners, there's also an after-school gardening club. All this, as he points out, depends on the school's head, who is passionate about giving the 400 children in the school the experience of growing their own food.

"It's all about the power and potential of outdoor learning," he says. "And eating." The children grow the kinds of things Moggach writes about in his book. Fresh green pea shoots fill a blue plastic mushroom crate. Coriander sprouts alongside. Fruit trees are just about to burst into bloom. This year they are going to make a compost heap.

And what does Moggach himself most like to grow, I wondered. "Shiso," he answered without a flicker of a pause. "A recent discovery and a total revelation. It's a herb not much used in the West, but immensely popular in Japan where it's used as widely as basil is in Italy." It's actually the plant flower gardeners call perilla and use, generally in its purple-leaved form, as an ornamental filler in bedding schemes.

Moggach recommends the green-leaved form, easily grown in a pot (minimum compost depth 15cm). Sow the seed in a sheltered spot in the sun, he says. Use a general-purpose liquid feed as the plants are growing. Harvest the youngest leaves for the finest flavour and use them to make a refreshing granita, or your own sashimi.

For more information about City Leaf, go to cityleaf.co.uk. To find out about Capital Growth projects go to capitalgrowth.org