High on a roof above a busy street in central London, in the shadow of the iconic BT Tower, something special is going on. A greenhouse glints in the sun, filled with tomatoes and climbing cornichons. A grapevine scrambles over a pale blue wooden pergola and Japanese wineberries clothe the walls. This space among the chimney pots is no more than 5 x 7m (16 x 23ft) yet somehow it manages to provide room for a tiny shed complete with writing desk and comfortable chair, a bench strewn with cushions, raised beds full of herbs and salad and pots galore. The paving-grade asphalt that once covered the surface is now decked with wooden squares infilled with pebbles. You wouldn’t think busy Oxford Street was a mere minutes’ stroll away.
This is an edible roof garden, but there are no rows of cabbages or potatoes. Owner Wendy Shillam, an architect turned nutritionist, instead chooses crops for “piquancy” — those that make a big impact when you eat them, but are only a small effort to grow. She divides these into three groups: fast-growing crops that look beautiful on the plate and are full of flavour, such as red basil or pea shoots; “watery” crops such as cucumber or tomatoes that taste best picked really fresh; and those full of protein, such as the beans she lets dry on the plant and stores for winter.
Most of the plants grow in only 15cm (6in) of compost in shallow raised beds. Others, such as the grapevine, are in larger pots. All are irrigated by an automatic watering system that comes on twice a day. This keeps the weight down to a minimum. This approach rules out root crops like beetroots, turnips and carrots — apart from stubby Chantenays, but most other plants are happy. “It’s volume of soil not depth of soil that’s important,” Wendy explains, “roots can spread outwards.”
The more she gardens on this rooftop, the more Wendy leans towards perennial edibles, giving less space to annuals or letting these self-seed around where they are happy. “I’m a very lazy gardener, and a very soft one,” she says. “If it seeds, it stays — that way you get pleasant surprises.” She points to the wild celery, parsley and French beans that have self-seeded in the shallow wooden-edged beds. Elephant garlic was planted once many years ago and has been a feature ever since.
Wendy is an expert at making the best of these precious ingredients. She uses her Par-Cel (Apium graveolens), or cutting celery, to make celery salt, crushing the seeds and adding them to regular sea salt for an herby kick and scattering the fresh leaves through salads and soups. The lavender is infused to make lavender sugar and the seeds collected in the autumn to add to muesli. Nasturtium seedpods are pickled like capers, others are left on the plant to set seed for next year.
“Work with nature, don’t try to control nature,” is Wendy’s mantra. True to her word, she uses no pesticides or chemical feeds – apart from organic liquid seaweed. Any slugs that somehow made it up to the roof are countered with liberal applications of coffee grounds and sections of chicken wire laid onto the compost that they don’t like to crawl over. “Sow a seed in each square and you’ll know exactly where you’ve sowed, too.
“I don’t go to the garden centre, I don’t buy compost,” says Wendy. Instead, to keep the raised beds and pots fertile, she makes her own compost in an old wooden chest insulated with sheets of polystyrene, with layers of twiggy sticks first, then prunings, banana skins, coffee grounds and other kitchen scraps laid on top. She mentally divides the box into three sections, rotating them so she knows which area is ready to use first. Sometimes she composts on the go, adding raw kitchen waste to the shallow raised beds, crumbling over eggshells to add lime and keep the soil sweet, and burying vegetable peelings just under the surface to rot down in situ for a couple of weeks before planting straight into it.
What’s the secret of gardening in this exposed rooftop? “Create shade, protect from the wind, plant like it’s the Mediterranean,” she says.
A bushy elderflower shields one corner from the wind, its berries making their way into homemade gin and the flowers into syrup. A low hyssop hedge forms an evergreen windbreak. Globe artichokes are a spiky and impressive screen at one end, immune to wind. The grapevine certainly looks happy and provides shade, too, on the pergola before turning stunning colours in the autumn. Other tall crops include a “Tromboncino” squash, climbing beans and nasturtiums. Additional sun protection is given by a cotton throw strung above her garden bench. So much greenery, so many pickings, but this roof terrace fits easily around a busy Londoner’s life. People say this garden must take an awful lot of time and I’m embarrassed to admit that I barely spend any time gardening,” says Wendy, “though I do spend many hours up here reading books.”
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Reprinted with permission from Crops in Tight Spots: Grow Amazing Fruit and Vegetables Wherever You Live by Alex Mitchell and published by Kyle Books, 2019.