One of the first things to find out about your garden is what sort of soil you have. This will be fundamental to the decisions that you make about the types of plants you grow as well as how to manage the soil. As well as identifying the soil composition (clay, sand, silt, chalk) you will need to find out how acid or alkaline your soil is.
Types of soil
There are four main types of soil – clay, sand, loam and chalk. The best way to tell which soil you have in your garden is to pick some up and mix it with a little water in the palm of your hand, trying to work it into a small ball. Does it feel sticky? Does it hold together well or not at all?
Feel sticky and will work into a ball when mixed with water
Are difficult to work in wet or very dry weather Are cold and wet in winter but may bake dry in summer Are slow to warm up in spring
Mostly high in nutrients although some trace elements can be ‘locked up’ by attaching themselves to the clay particles
Feel gritty and will not hold together when mixed with water to make a ball
Are easy to dig even during wet weather Are free draining in winter but become dry and dusty in summer Warm up quickly in spring
Leach nutrients quickly due to the free draining nature of these soils Sandy soil is often acidic
Are between clay and sandy soils. The soil may hold together when rolled into a ball if it is a ‘clay loam’ but won’t if the soil is a ‘sandy loam’ Loam soils with a high clay content are known as ‘heavy clay loam’ and those with a high sand and silt content are ‘sandy loam’
Are easy to dig once the surface has dried out Hold nutrients well and tend not to ‘lock up’ trace elements
Lumps of white chalk or flint stones are visible in the soil
Are either ‘heavy’ or ‘light’ depending if the soil mixed with the chalk is clay or sand Alkaline soils The soil fizzes when added to malt vinegar, showing the calcium carbonate content
These soils are often ‘shallow’ with little depth of top soil
These are the most common types of soil found in gardens and all have their advantages and disadvantages!
Checking your soil pH (acidity)
Once you have decided on the type of soil that you have, look at your existing plants or in nearby gardens at the types of plants that are growing. Are there lots of Rhododendrons, Azaleas and Camellias, along with Pine trees and blue flowers on Hydrangeas? This is a sure sign that the soil is acidic – a must for ericaceous plants. If you are still not sure, most of our centres offer free soil testing. Find out more on our Services page. Alternatively, pick up a soil testing kick online.
pH 3.0 to pH 5.0
- Very acid soil
- Nutrients are either more soluble, therefore washed away easily, or ‘locked up’ making them unavailable to plants. These soils are deficient in nutrients
- Most plants find it difficult to grow in very acid soil
- Top tip! Add lime to raise the pH to 5.0
pH 5.1 to pH 6.0
- Acid soil
- Ideal for lime hating (ericaceous) plants such as Camellias, Heathers, Azaleas and Rhododendrons
- Add lime if other plants are grown and for vegetables and fruit
pH 6.1 to pH 7.0
- Moderately acid soil
- This is the ideal pH for a wide range of plants, except lime hating plants
- It is not usually necessary to add anything to the soil to change the pH
pH 7.1 to pH 8.0
- Alkaline soil
- Iron and manganese become less available to plants leading to yellowing of the leaves (chlorosis)
- Iron sulphate and other acidifying agents can be added to reduce the pH. Chalky soils are usually not treatable
You will now have an idea of the type of soil in your garden and the pH (acidity). For instance, you may have a heavy clay loam that is slightly alkaline or an acidic, sandy soil. All soils benefit from the addition of bulky organic matter, whether during the digging process or by mulching in spring or autumn. You could manufacture your own bulky matter by starting a compost heap!