However difficult a soil or situation may be it is usually possible to find some plants that will grow in it. But this is only one way of dealing with this problem. Another is to improve the condition that is causing the difficulty and so widen the selection of plants that can be used successfully. Chalk soils are limiting because they are often deficient in iron and manganese which suffer chemical changes that render them insoluble and therefore unavailable as plant food. Special preparations of these chemicals, known as sequestrols, can be used to make good the deficiencies and the soil can be made less alkaline by giving it heavy dressings of acid peat or leafmould.
Heavy clay soils are difficult because they retain too much water, are poorly aerated and tend to become sour. Generous liming will improve their texture and correct sourness, but it can make it difficult to grow lime-hating plants such as rhododendrons, pieris and many heathers. Peat, well-rotted garden compost, stable manure and coarse sand will all help to improve the texture of clay soils.
Plants growing in seaside gardens are often battered by gales which may bring salt spray as an added hazard. Here the remedy is to provide a substantial windbreak on the seaward side. There is nothing better for this than Cupressus macrocarpa, which grows rapidly and is evergreen. The yellow-leaved variety is even more salt resistant than the green. Pinus radiata is a fast-growing pine that does well by the sea and makes a tall and substantial windbreak. While such plants are growing temporary shelter can be provided with wattle hurdles or interwoven fencing. In very hot sunny places improvement can be effected by planting trees to give some shade, but since in such places dryness is often as damaging as the intensity of the sunlight, the trees must be planted sufficiently far away not to fill the flower beds with their roots. Some kinds such as the cypresses do not make very extensive root systems, and some such as oak push their roots downwards rather than outwards and these are to be preferred as shade givers in such places. Water sprinklers permanently installed can also transform the planting possibilities in a hot, dry garden. Sprinklers that give a fine, rain-like spray are the most satisfactory as the water then has time to soak in.
Plants that spread densely over the surface of the soil are often recommended as ground cover to smother weeds and so save labour. This works well provided the soil is well cleared of weeds first and any perennial weeds that appear later are removed promptly. But if weeds are allowed to become established under the ground cover it can be a major operation to get rid of them.