Clay soils tend to be more or less dark brown in colour and become sticky when wet. This soil hardens to something resembling concrete in dry weather. They are usually rich in nutrients and make a good growing medium with added soil improvers, especially organic matter.

White chalky clay, is an extreme example. It is a very poor soil and presents real problems. The clay does retain water and prevents mineral salts and fertilizers from draining away into the subsoil. However soils with a high clay content are difficult to work and take a long time to heat up in spring. That is why they are described as 'heavy' and 'cold'. Spreading and digging in coarse sand can improve soils with a high clay content. Adding peat, peat substitute, manure or compost can lighten clay soils lacking in organic matter.

Those with a low chalk content can be improved by adding garden lime before they are dug over. More lime can be added to the surface after planting over a period of three to four years. Bear in mind that these methods of improving the soil are effective only up to a depth of approximately twelve to sixteen inches. If you want to plant trees and shrubs in a clay soil, it is advisable to choose varieties whose roots are not affected by moist, heavy soil.

Sandy soils generally have a fine grained silica base and retain very little in the way of water, fertilizers or nutrients which means they are extremely poor. Once they have dried out, they are difficult to moisten and can only be revitalized by the addition of organic matter. My area is very sandy and when creating new gardens I always purchase the best topsoil available. However sandy soils are light and easy to dig, hoe and weed.

They warm up rapidly in spring and seeds germinate early. They allow water to drain through too quickly and nutrients tend to be washed away. A very sandy soil can be given body by digging in good clay soil. It is essential to add large quantities of organic matter, peat, peat substitute, leaf mould, compost or manure. Also you have to water regularly. In this type of soil, fertilizers should be added several times a year.

A sandy soil which is too acid can be improved by adding garden lime. A well-improved sandy soil is ideal for growing vegetables; bulbs and annuals while a number of conifers also prefer light, sandy soils.

Apart from chalky clay, chalky soils are light brown to white in colour. They contain large quantities of variously sized stones which have come direct from the parent rock. As they tend to block trace elements (especially iron) they are extremely poor and require large amounts of soil improvers and regular additions of fertilizers.

However chalky soils warm up quickly in spring but do not retain water. They dry out in summer and are poor in nutrients. Like sandy soils, they require large amounts of organic manure and balanced fertilizers. Their high alkalinity tends to cause chlorosis in a number of plants, this is a disorder characterized by yellowing of the leaves, while the veining remains green and plants lose their leaves and become weak or die.

It is essential to grow only chalk tolerant plants, as it is unrealistic to expect to neutralize the effects of the high alkalinity. Vegetables are reasonably chalk tolerant as are a variety of perennials.

Humus-rich soils are rich in well-rotted, organic waste. They are dark brown to black in colour, very light and extremely air and moisture retentive. Roots love this type of soil, although it is not particularly rich.

Humus-bearing soils are often acid and require a chalk based soil improver when their pH is below 6.5, except when used for growing acid loving plants such as rhododendrons and camellias. Woodland soils are typical humus-rich soils. They are rich in leaf mould and although permeable soak up water which is in turn absorbed by the plants. They warm up quickly in spring and are easy to work. However they are often extremely acid and suited only to certain types of plants.