The most important element to consider, when starting a planting plan, is the soil. Soil provides anchorage for plant roots and holds the water and nutrients that are necessary for maintaining life. It is made up of numerous elements.

Rock Particles

All soils except peat are mineral soils formed from rock particles. They have been ground out of the rocks on the planet’s surface by the relentless action of rain, wind and frost. The size and shape of the particles vary according to the parent rock and the weather action, so that different types of soil are formed: clay, silt, sand and chalk. Each type of soil has different qualities of aeration, drainage and nutrient holding capacity.

Humus

The product of decayed and decaying plants and animals, humus or ‘organic matter’ is the magic ingredient which gives fertility to the soil. Humus improves the structure of the soil, making it dark brown and crumbly. It holds moisture without impeding drainage and is home to a wide range of bacteria and other micro-organisms that help the gardener by breaking down organic matter to release plant nutrients. Earthworms thrive in humus-rich soils, and their movement through the soil aids drainage and aeration.

The proportion of humus to mineral particles varies in different soils. It can be added to poor soil in the form of well-rotted manure, compost or leaf mould.

Water

Entering the soil by precipitation (rain and snowfall), by absorption upwards from the underground water table and by seepage from rivers, lakes and ponds, water is lost from the soil through natural drainage, through evaporation and through plants taking it up through their roots. Plants need access to water for their food-making process of photosynthesis.

Air

Plants breathe through their roots, using the air trapped between the particles of rock and humus. Without air soil becomes waterlogged, suffocating plant roots. The living organisms in the soil, on which plants depend, also need air.

Acid and Alkaline Soil

Soil with a high lime or chalk content is alkaline (7.5-9). When lime is not present, it is neutral or acid(5.5-6.5). Peat is acid, as are most clay soils. Acidity and alkalinity is measured in terms of the soil’s pH.

Neutral or nearly neutral (6.5-7.5) soils are ideal for most plants. At this pH level nutrients are readily available. Some plants prefer alkaline soil and a few will only thrive in acid soils (See Plants section).

Types of Soil

• Clay Soil - Slow to dry out after rain. A lump squeezed in the hand feels dense, sticky and pliable like the clay used in pottery. Clay soils are known as ‘heavy’ soils. Clay can be acid, neutral or alkaline.
• Sandy Soil - Dries out quickly. Disintegrates when handled. Sandy soils are ‘light’. Nutrients and lime are washed away, so sandy soils tend to be acid.
• Peaty Soil - Holds water like a sponge. Usually acid and not very fertile.
• Chalky Soil - Drains rapidly washing nutrients away. Very alkaline; the white parent rock is often close to the surface.
• Limestone Soil - Drains rapidly. Numerous stones are present, from tiny ones to large rocks. Alkaline but less so than chalk.
• Perfect Garden Soil - The best all-purpose soil is known as loam. It is a balanced mixture of clay and sand with plenty of humus and is neither acid nor alkaline. Soils are usually described in terms of their relationship to this ideal, for instance sandy loam, clay loam, silty loam.