Monday, October 15, 2007

Gardens in dry, free-draining soil

In free-draining soils you can grow a range of plants that are not happy in moist conditions. Since rain soaks through fast, you can dig and cultivate the soil almost at any time - even after heavy rain, when clay is too boggy to work on. However, with excessively free-draining soils, such as sand or gravel, it can be a time-consuming chore to keep plants moist. 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 a good selection of drought-proof, self-seeding flowers, such as Californian poppy, coreopsis, evening primrose {Oenothera biennis), gaillardia, Livingstone daisies, nasturtium and native everlastings. 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 in 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
When preparing a dry border for planting, add organic matter to improve the water-holding capacity and nutrient content of the soil. In problem sandy or chalky soils, which are particularly 'hungry', dig in organic matter in autumn, and then each spring apply 140g per square meter of any complete plant food, or use a rose fertilizer and mix it into the soil.

For very thin soils, where there is rock just below the surface, you will need to increase the depth to obtain water retention. Mix good-quality topsoil with the top few centimeters of garden soil, incorporating well-rotted organic matter as you go, to increase the soil's depth. Plant in autumn or spring and keep the new plants watered. Before planting, soak the root-ball of each plant. After planting, apply a 5cm 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.

Some more tips for dry soil
  • Choose drought-proof plants.
  • Conserve moisture by mulching in spring when the soil is moist.
  • Mulch problem soils twice a year, in spring and autumn.
  • Build a deep, no-dig bed if you want to grow fruit and vegetables.
  • Don't try to grow a conventional grass lawn. Instead, create patches of green with a herb lawn using thyme or chamomile.

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