Your most important task as a gardener is to gain an understanding of soil. Your soil type determines what will grow well and what will fail, so save yourself heartache and miserable plants by spending a little time getting to know the soil in your garden and how to make the most of it.
Testing your soil
There are two main types of soil particle: sand and clay. Sand particles are relatively large and water drains freely through the spaces between them, while clay particles are tiny and trap moisture in the miniscule gaps. They are also slightly absorbent. This explains why sandy soils are dry and clay soils are moisture-retentive.
Most soils are a mixture of both, but tend toward one or the other, but the ideal is “loam,” which contains almost equal measures of sand and clay. Loam retains enough water for plant roots to use, but also drains away excess moisture to prevent waterlogging. Test your soil type by digging some up and rolling it between your fingers.
When rolled between the fingers, sandy soil feels gritty, and when you try to mold it into a ball or sausage shape, it falls apart. It is also generally pale in color. The benefits of sandy soils are that they are light and well drained, and easy to work. Mediterranean plants are happiest in sandy soil, because they never suffer from soggy roots. However, their poor water-holding capacity makes sandy soils prone to drought and lacking nutrients because nutrients are dissolved in water.
Roll clay between your fingers and it feels smooth and dense, and retains its shape when molded into a ball. Soils very rich in clay will not crack even when rolled into a horseshoe shape. Sticky and impossible to dig when wet; solid, cracked and impenetrable when dry, clay soils are hard to work. But in return, when looked after correctly, they have excellent water retaining properties, and are rich in nutrients. Greedy rose bushes and fruit trees love to sink their roots into them.
Improving your soil
Whether you have a dry sandy soil or a sticky clay, the prescription is the same: lots and lots of organic matter, such as well-rotted manure, spent mushroom compost, and garden compost. These bind together sandy soils and loosen dense clay soils, so ladle them on.
Horticultural grit helps improve drainage in clay soils. Dig it into the soil over a large area, rather than using it to line the base of planting holes. In heavy downpours grit-lined planting holes act as sump pumps and water pools around the roots of plants, which can kill them.
A simple pH test, available from the garden center, will tell you how acidic (lime-free) or alkaline (lime-rich) your soil is, and this will determine the range of plants you can grow. Add the supplied solution to a small sample of your soil in the tube provided. Wait until the solution changes color, then match the color to the chart.