Garden Advice

How to Improve Clay Soil – The Complete Guide

Clay soil, also known as “heavy soil” comprises of large quantities of clay particles, which can often make it hard to manage. For example, clay soil lawns are known to have drainage issues. This is a consequence of them being too dense and compacted. Aside from being prone to sogginess when wet, clay soil can also turn rock hard in summer thanks to the sun’s strong and scorching rays.

With that, all said, however, clay soil has many benefits if looked after correctly. First off, it’s very fertile and secondly, it holds in nutrients longer than regular soil, making growing woody plants a walk in the park. However, getting the perfect clay soil lawn is not so easy.

Since soil texture is an essential property that is unchangeable, you have to work on improving your clay soil’s structure over a long period of time. And we’re here to help you do just that.

Table of Contents:

So if you

  • Are living in the UK and are wondering how to improve your clay soil
  • Want to learn how to improve your clay soil’s drainage
  • Are wondering if gypsum can improve clay soil

Then you’ve come to the right place!

Identifying clay soil

Clay soil isn’t too hard to identify. Unlike regular soils, clay ones feel a bit sticky and dense. When you rub clays between your index finger and thumb, the texture feels smooth (unlike the gritty feel of normal soil).

To test the texture of your clay soil a tad more, add a bit of water to a piece of it. Roll it into a ball shape and then into the shape of a finger, without cracking it. Does the finger-shaped clay soil become shiny when rubbed? If so, it’s likely very rich in clay (heavy clay).

What tools do you need to improve clay soil?

Before we go on to actually improving the soil, you’ll want to make sure that you have the tools needed to complete the job. You’ll need: 

  • Trusty gardening gloves
  • Spade
  • Broadfork
  • Digging fork
  • Lawn aerator 

Improving clay soil

Ok, so now you know what clay soil is and what it looks like, but you’re probably asking yourself, how does one improve it? Well, it all starts with some work on the soil’s structure.

Soil structure is determined by the way the soil’s particles are assembled as aggregates. When it comes to clay soils, the clay particles are usually organised on a horizontal plane and under a platelike structure. If those horizontal aggregations keep getting stacked high and are consolidated over time, they can turn very firm and sticky.

Clay soil improvement is a consequence of looser and more granular structural aggregation. Such clay soil has brittle consistency and excellent tilth. And we have all the tips and tricks to help you achieve it.

  1. Dig over your soil during autumn

    September is a great time to turn over your soil, with a fork, as it shouldn’t be too damp. However, don’t break up the lumps. It’s better if you allow the winter frost to do it, as it will result in finer tilth.

  2. Don’t walk on the soil

    Remember that clay soil becomes compacted when under pressure. Therefore it’s important you avoid walking on it. What you can do, however, is stand on a plank when digging or you can work on your soil when it’s a bit dryer. Consider laying stepping stones connecting the different areas of the garden, which will help maintain soil integrity. 

  3. Aerate your soil

    Aerating your soil at least twice a year (Autumn and Spring) will help keep your soil healthy, by improving drainage, allowing helpful micro-organisms into the soil and breaking down compacted clay soils. Simply poke holes in the soil as deep as possible in regular intervals. It is especially important to do this in Autumn, as it helps combat any changes in the soil caused by gravity and compaction, keeping it healthier for longer. 

  4. Do your planting in

    Clay retains a lot of moisture during the cold seasons, so planting anything in autumn should be a no-no. Spring, on the other hand, is the ideal time of the year to start planting. As the weather warms up, so does the ground. When you’re done planting, water the soil well, to avoid droughts.

  5. Mulch it!

    It’s common knowledge that when clay soil experiences drought, cracks begin to appear. To prevent this occurrence, mulch your clay soil lawn around late spring when the soil’s still moist and warm.
    Choosing the right type of mulch can work wonders here. You can use fine bark to achieve good results. However, know that when bark decomposes, it robs the soil of nitrogen. But, that can be easily avoided by adding nitrogen-rich fertiliser before applying the mulch to the soil. Repeating this each year will seriously improve your clay soil.

  6. Add a cover crop

    Cover soils are great at improving soil structure, amongst a host of other benefits, which include promoting soil biodiversity and the ability to reduce erosion and water movement. They can be used to improve clay soils too, especially if you choose a cover crop known for its deep root penetration. This is because it can help break down soil compaction in the sub-layers of clay. 
    Consider adding buckthorn, borage, clover or our personal favourite, comfrey, to break up heavy soils. Plus, it’s a good way to spice up your garden, by covering any bare soil. 

  7. Build a raised garden bed

    Raised garden beds are a great option for people planning to start a vegetable patch. They offer better drainage and help warm the soil quicker in spring.

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How to improve drainage in a clay soil lawn

Draining clay soil is a laborious task, that takes time and patience. One way you can go about it is to dig in horticultural coarse grit into the soil. This can help sustain your soil for several years. Another way of improving drainage in clays is by adding garden compost, as that will make it airier. But beware, garden compost usually lasts for around two to three years, after which it begins to rot.

Keep on reading for more tips on drainage improvement in clay soil.

Dig larder holes when planting
At the end of spring, when it’s time to sow, dig a hole twice as big as a rootball (so that the roots of your plant grow at ease). Then using a fork, break up the bottom of the hole as to improve the soil’s drainage.

Sow woody plants on a mound
When planting woody plants in clay soil, start by creating a mound of soil. Then sow your plants in that mound. This will help improve the drainage.

Aerate and scarify your clay soil lawn
Moss and worm casts can harm your clay soil lawn greatly, therefore it’s important you deal with them quickly. Use a wire rake to remove the thatch off the lawn in autumn, then scarify it using a fork or scarifier(to create drainage holes). If that seems to you like a lot of work, then you can book our lawn aeration and lawn scarification service.

You may also like:
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How to Fix a Waterlogged Lawn

Adding organic matter to your clay soil

Is adding sand to clay soils a good idea?

Although it’s often recommended online to add sand to clay soil to make it easier to work on, don’t do it! When mixed with sand, the clay soil’s structure changes, it turns rock-hard and is nigh impossible to work on.

Adding gypsum to clay soil

Gypsum works wonders on clay soil. It helps break it up into small and crumbly chunks, in turn making it easy to work on. An added benefit of using gypsum is that it can improve the clay soil’s drainage.

  • The trick here is to apply 1kg of gypsum per every square meter of clay soil, digging it into the top four inches(10 cm). If the soil is very rich in clay, you might need to repeat this more than once.
  • Next, step up your compost game. Dig in large quantities of organic compost into the soil and then spread it at about two inches(5 cm) deep. Turn the composted soil using a fork to around four inches(10cm) deep.
  • After you complete the steps, give the soil a few weeks to settle(do not disturb it). The combination of gypsum and compost will help improve the clay soil’s structure.


  • Improving a clay soil’s structure takes time and patience and won’t happen overnight.
  • Clay soil drains harder and requires you to do the work, from digging holes to aerating.
  • Organic matter such as gypsum, grit and compost can help make your clay soil more easily drainable and improve its structure.


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Image source: Sergey Vasilev 2701/

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