There are several solutions – choose naturally drought-resistant plants, improve the soil so that it retains more moisture or install an automatic watering system. Free-draining soils can run short of certain nutrients because they are soluble and are literally washed away.
Choosing drought-tolerant plants When drawing up a planting scheme for dry soil in sun, include plenty of drought-proof self-seeding flowers, such as California poppy, Eryngium giganteum, Euphorbia dulcis ‘Chameleon’, E. characias ssp. wulfenii, evening primrose (Oenothera biennis), Linaria purpurea, nasturtium, Onopordum arabicum and Verbascum bombyciferum. If you leave self-sown seedlings to grow where they come up, you will not have to water them. If you transplant seedlings, no matter how carefully, the roots will be disturbed so they must be kept watered until they are established. Even pot-grown, drought-tolerant plants need to be watered for the first few weeks after transplanting.
Many tender perennials are drought-tolerant, such as gazania, mesembryanthemum, osteospermum and pelargonium. If you want to grow non-drought tolerant bedding plants on dry soil, dig into the soil well-rotted organic matter or water-retaining gel crystals – usually used in hanging baskets – to help the soil to hold water. To grow fruit and vegetables on dry soil, build a deep bed filled with compost and install a watering system.
Improving Dry Soils
Improving dry soils When preparing a dry border for planting, add organic matter to improve the water-holding capacity and nutrient content of the soil. On problem sandy or chalky soils, which are particularly ‘hungry’, dig in organic matter in autumn, and then each spring apply 140 g per m2(4 oz per sq yd) of general fertiliser such as growmore – or use a rose fertiliser – and mix it into the soil.
On very thin soils, like those sometimes found over chalk, mix good-quality topsoil with the top few centimetres of garden soil, incorporating well-rotted organic matter as you go, to increase the soil’s depth. Plant in autumn so that winter rains keep new plants watered. Before planting, soak the rootball of each plant. After planting, apply a 5 cm (2 in) mulch of well-rotted organic matter. If you do not have time for regular soil improvement, restrict your choice of plants to the more drought-tolerant types.