Soil Types Explained: What soil type do I have?

Updated 2020: The soil type that you have in your garden can make or break your plans for a successful garden design.  Your plants will only be as successful as the preparation and planning that you, the gardener puts in! Rather than thinking of soil as dirt, you need to start treating it as the life force of your garden. Where all microbes bacteria and microorganisms live, allowing your plants to grow successfully.

The last thing you want to do is to spend hundreds of pounds on your garden to find all your plants wilting or dying. Establishing the type of soil is paramount in making sure that you’re selecting the right plants, fertiliser and conditions for growth.

Let’s take a look at the types of soil you may be dealing with and how best to work with them during your gardening.

Soil Types Explained

1. Soil Terminology Explained
2. Soil formation – how soil is made
3. Types of soil
4. What is the perfect soil mix?
5. Sandy soil
6. Clay soil
7. Silty soil
8. Checking what soil type I have
9. Improving compacted soil
10. Soil PH explained

1. Soil Terminology Explained

Understanding why soil is such an important part of your garden is essential. Often soil is confused with dirt or garden compost. However, soil is neither of these. Soil is its own organic living organism. Whereas dirt is inert material and compost is organic matter that is breaking down. Let’s have a closer look at the key soil terms below.

Dirt

Bits of inert debris, grit, rock and sand with no organic ie living matter.

Soil

Soil is a complex mix of particles, minerals, living organisms, dead organic matter and bedrock (ground down stone). It creates a rich living tapestry perfect for plants and wildlife to thrive in. It’s the building blocks of all successful gardening and garden design.

Loam

Loam is the ‘near perfect’ healthy mix of clay, silt and sandy particles found in soil. Think of it as the ideal mix of balance, but rarely achieved! 40% Sand, 40% Silt and 20% Clay. It’s a sub term for soil.

Compost

Compost is organic matter that has been broken down naturally in a recycling cycle. It means its high in nutrients, holds onto moisture and contains a light airy texture. You can make your own compost at home to help boost your soil health.

2. Soil formation – how soil is made

The soil is composed of both organic (dead & living) and inorganic (mineral) elements. It’s created over time and is present in layers known as soil horizons, which if you dig down you can see. It composes of tiny fragments of stone which have been weathered either by the elements or by organisms such as lichen eating away at stone surfaces. These tiny fragments are then built up over time in layers mixed with organic material creating layers of types of soil.

The organic matter usually comes from trees dropping leaves, plants dying back each year, animals grazing and dropping their own natural manure. It is an ever evolving situation of things growing and then decomposing that creates soil.

Soil Horizons

Soil horizons start with the very top organic layer, moving onto topsoil, which most people are familiar with the next layer being subsoil and then lastly the parent material such as solid rocks, sands and gravels. Don’t worry the science lesson will soon be over but it is important to understand this to know why knowing your soil type is important.

A gardener is concerned with making sure that the structure of the soil is open, free-draining, contains organic matter (for both nutrients and moisture retention) and is easy to work with. This is a fine balance and over-cultivation, ie digging the soil too frequently can do more harm than good! Which is why a number of gardeners, myself included, are choosing to follow ‘No dig’ gardening principles.

3. Types of Soil

This refers to the amount of Sand, Silt and Clay present in a soil sample.

Most people will have heard of sandy, silty or clay soil types.  Maybe referring to their own soil as heavy clay or very sandy. These are the mineral fractions of the soil and contain no organic matter themselves.

In reality, soil is a mixture of these elements along with organic matter and the mineral elements all of which dictate how the nutrient or organic elements are contained or lost. The type of soil will determine how easily they hold onto water and nutrients. Which is why it’s important to know what soil type you are working with!

4. What is the perfect soil type?

Loam is the technical term for the perfect soil. Whilst there are subclassifications such as sandy loam, clay loam and silt loam this general term is used for a free draining soil that as a ‘perfect’ blend of the three main components. Very roughly, so the horticulturists don’t kill me, loam is

• 20% Clay
• 40% Silt
• 40% Sand

What type of soil do I have?

Your soil type will be a mix of Sand, Silt or Clay. Though the weighting of each element takes a much closer inspection and test. The classifications below are not exact but give you the benefits for each soil type. I always advise that a garden survey is the best way of working out the soil types and PH which I offer in all my Garden Design service. By establishing what soil you have this will in turn lead t your plant selection.

5. Sandy Soil

• Very easy to work with
• Free draining
• Requires more watering
• Loses nutrients quickly and doesn’t hold its shape well]
• Particle size 0.5-2mm

6. Clay or Heavy Gley Soil

• Fantastic at holding onto nutrients
• Soil sticks together and doesn’t erode as quickly but is difficult to dig and work with
• Can retain too much water becoming waterlogged
• Growth can be affected especially in annual plants (Plants that grow flower and die within one year/season) as they may struggle to establish.
• Particle size 0.002-0.5mm

7. Silty Soil

• Fairly free draining, silky to the touch
• Contains a good level of nutrients
• Retain moisture well due to small particles
• Prone to compaction/erosion and can become solid or crusty quickly
• Particle size 0.002mm and below

8. How to check what soil type I have

The above should help you in assessing roughly what soil type you have but ideally, you need an expert as it isn’t just the soil type but also the aspect, PH and other environmental factors that will affect the success of your garden design. By taking a handful of soil and squeezing it when slightly wet you can usually get a good idea of whether it is:

1. Sandy will fall apart in chunks
2. Clay will squish like playdough in a solid mass
3. Silt will feel almost creamy, soapy and silky when compressed

Sandy soil will drain really quickly so this can be an indicator. If you dig a hole one spade depths deep then pour in a watering can of water then sandy soil should drain within an hour whereas clay won’t.

Soil that is silty is in the minority and usually found near river beds or old water courses. Most soils in the UK are either sandy or clay based.

Why does soil type matter?

It matters because if you, for example, have heavy clay soil you are going to struggle to grow bulbs, annuals or lightly rooting plants as clay is dense and difficult to work with. They will simply rot given its high water retention. You will need to work in a considerable amount of organic matter to such soils to help aid aeration and drainage.

You will, however, be able to grow moisture-loving plants such as Iris pseudacorus in clay soil. So you can see how the right plant for the right place comes into play. You’re not going to be able to completely change the soil type, only tweak it. It is best to work with what you have got. You will need to assess the

You will need to assess the planting scheme you want for the soil type you have. It’s not impossible to completely change your soil type, it is highly improbable given the fact you would have to fully remove it all with a digger to replace it!

The only way to work with it is via organic dressings and some very specific planting plans that cater to your soil type. Finding plants that will tolerate or even thrive in your soil type can save you much heartache and ensure you spedn more time enjying your garden rather than grieving over plants! Garden Ninja can help assess soil types and provide suitable planning schemes for this with my design services.

9. Compacted soil & how to improve it

So we’ve talked about the fantastic life force of soil. How soil provides the very elements that your plants need to survive, stability, food and water. However, when the soil has been over-cultivated or walked on repeatedly it can become compacted. Like a concrete road of firm grit. It often goes a grey colour as the top layer develops a soil cap. A soil cap is a hard crust that prevents water and organic matter from entering or leaving the soil. It’s a prison for the soil organisms.

If you have compacted soil the advice is to cultivate it and add organic matter such as compost or lawn clippings. By adding a small amount of this it helps keep the air spaces relatively free in the soil, the party starts again with all those microorganisms and you’re ready to plant for success!

Once cultivated you soil should look healthier, darker in colour and much lighter to work with. Be careful not to then start walking repeatedly over it and compacting it again. If you need to walk that route consider a path or using boards to walk on to protect the soil.

10. What is soil PH & how can I check it?

Soil PH is again incredibly important as this will show whether your soil is acidic, neutral or alkaline. Plants do have a preference for the PH of the soil so accurately assessing what the PH is can save you time and money with plant choices. There’s no point expecting an Azalea to grow in an alkaline soil bed when they are ericaceous or acid-loving, likewise, there is no point trying to force alkaline loving plants in acidic soil.

Most UK soils are between 5.5 and 7.5. The lower register is more acidic and the higher the more alkaline the soil type. However, you may find that different parts of your garden have different PH’s. So it is worthwhile making checks across your garden in different places and recording the results.

It must be stressed that most plants are perfectly happy in this 5.5-7.5 position. There are a few exceptions.

Ericaceous/Calcifuge Plants

Some plants prefer acidic or ericaceous soil below 5.5. Usually plants from moors, dry heaths and peat bogs where acidic conditions are present. They have adapted to be able to take up nutrients available in acidic conditions. eg – Erica carnea (Winter Heather).

Alkaline/Calciole Plants

Other plants are adapted to more ‘chalky’ soils where alkalinity is high. eg – Convallaria majalis (Lily of the Valley).

Alternatively, you can buy over the counter soil testing kits. These vary from mixing soil with a solution using litmus paper to assess the PH or electronic probe PH testers. Ideally, you would need multiple checks around each border to ensure you have a proper view of your gardens soil type.

Take your time as each test can take around 10 minutes. Map out the PH readings on a plan of your garden site to ensure you know exactly what to plant where.

Summary

Understanding your soil type and how its created is a really important part of becoming a successful gardener. Many gardeners ignore soil at their peril and end up with lacklustre planting results. By taking some time to get to know soil and treating it as a precious resource you will become a far better and mindful gardener.

If you have questions on your soil type why not Tweet, Facebook or Instagram me with your pictures! You can also follow me on Youtube where I’ve got plenty of garden guide vlogs.