The tropics of Soho
In creating a roof garden — or any outdoor space for that matter — there is one mantra to follow: go for impact, with every plant and every feature. So believes landscape designer John Bailey. ‘I like to use large statement plants that create an instant and dramatic landscape’, he says. ‘They are more expensive, but it is money well invested. Even in a small space, I believe you should think grand, and let the space live up to the plants.’

Glamour
This 60ft-long roof garden for a model agency in Soho, which, not surprisingly, demanded glamour for its garden. ‘The usual wisdom is to group plants in odd numbers and, although this works if you’re planting perennials in the border, you can raise the profile of areas in the garden, almost redesigning the space, if you site plants in pairs.’ In this roof garden, as you first walk out, there is a pair of Trachycarpus palms on either side of the arched entrance, looking as if they are guarding it. Two clumps of triple-stemmed banana trees are placed on either side of the steps leading to an outsize table further down, which is surrounded by a grove of yellow-stemmed bamboo, planted in two deep tanks on either side. ‘You can also raise the profile of a central feature plant, wherever it is, by using smaller plants in even numbers on either side, that gradually trail off.’

Impact
Take another look at the banana trees, and there is a further surprise: where we might under plant a box bush with a ruffle of busy lizzies, Bailey has under-planted the bananas with variegated phormiums, so that the banana leaf canopies appear to spring out from the fans of stripy cream-and-green flax foliage; this is impact planting on the grandest scale. If you make this kind of statement with plants, the design needs to be equally strong, with symmetry playing a key role; straight, sure lines win out over gentle curves. In this roof garden, you step out onto a rectangular deck that is quartered with four skylights from the space below, with a table and chairs sited slap-bang in the centre. Beyond this is a rectangular gravelled area, the furniture and plants set in perfect alignment.

Unfussy
Keep the landscape unfussy too, advises Bailey. ‘I restricted landscape materials to two: decking and gravel, both of which work well with these kind of exotic plants, and make a striking contrast to one another.’ Painting walls white is a useful device for making a small dark patio appear larger and brighter, but it is not the only way to go. ‘Black adds drama and has the bonus of making boundaries disappear.’ In this garden, the striped red-and-pink leaves of Canna Durban and yellow bamboo look wonderful against it; the yellow bamboo, Phyllostachys vivax aureocaulis, is planted in a black plastic water tank from a plumbers’ merchants. The large wooden table is painted black to make an unobtrusive canvas for plants, as are the air-conditioning units concealed behind a wooden screen.

Specialist care
Exotic foliage plants need no specialist care, says Bailey, but beware of thinking that because date palms belong in the desert that these kind of plants need little water. ‘Even in the desert there are reserves of water underground. And the hardiest palm that is ideal for our gardens, Trachycarpus fortunei, actually comes from cold parts of China, and grows well in the shade.’ It needs lots of water, especially in the first few seasons, as do banana trees. If your outdoor space is not sheltered, look for a newcomer to our shores, Trachycarpus wagnerianus, which has shorter, more wind-resistant leaves. For smaller container and tabletop plants he favours cacti and succulents, including the glossy black Aeonium Zwartkop, agaves and sempervivums. ‘Forget to water them, and they’re perfectly happy, which is a real bonus when they’re on a roof.’