THE SELF-RELIANT GARDEN

Like many small urban spaces, Charlie and Ben’s roof garden is planted entirely in pots and has to withstand long periods without watering. This is how they help the plants thrive: Use large containers – particularly for trees and climbers – so the compost dries out slowly. Reclaimed water tanks around 60cm each way, and dolly tubs are deep enough to retain moisture for long periods. Water tanks are also slightly narrower at the top, which reduces evaporation. Choose drought-tolerant plants. Verbena bonariensis, agapanthus, lavender, nepeta, sedums, pelargoniums, nasturtiums, foxgloves and nicotiana all cope well with the infrequent watering. Use a good peat-free, multi-purpose compost – such as New Horizons – and, if you are going away, a ‘dollop’ of liquid seaweed feed on your return to give the plants a pick-me-up. Ensure you have decent water pressure, especially if you are gardening on the roof of an old property. Charlie and Ben use a water tank topped up automatically from the mains, which is tucked under the steps to allow fast filling of watering cans. If growing edibles, choose Mediterranean herbs (rosemary, oregano, thyme and sage), perpetual spinach, chillies, garlic and wild rocket that can cope with infrequent watering. Don’t be too wedded to anything. Be prepared to replace casualties. Encourage plants that do thrive in the conditions by allowing them to seed in situ.