How to improve clay soil for gardening - boost your garden's health and help plants thrive

Learning how to improve clay soil for gardening will increase the health of your flowers and the yields of your crops.

Thankfully, it's not as difficult as it first appears – there are short-term labour-intensive methods and more long-term but low-effort techniques, meaning you can choose the right approach for your garden ideas.

How to improve clay soil for gardening

The first step in improving clay soil for gardening is to confirm that you have clay soil. This is very easy to do – with no need for specialist tools. 'Take a handful of soil and squeeze it your fist. If the soil remains in a tight ball and is an orange-brown colour, you have quite heavy clay soil. This tends to stay wet in winter and bake hard in the summer,' explains landscape gardener Paul-Hervey Brookes.

Clay soils have a bad reputation as they can quickly become waterlogged during winter and dry out to an almost concrete consistency during summer, making it hard to grow some plants.

However, once you know how to improve clay soil for gardening, you'll be rewarded with an excellent growing medium. 'Clay can hold water and nutrients tightly due to its fine particles and high plasticity,' explains Julian Palphramand, Head of Plants at British Garden Centres. This means it can be very fertile and is one of the best soil types for resisting drought.

1. Add organic matter

'The simplest way to improve clay soil for gardening is to incorporate bulky organic matter such as compost or farmyard manure, as well as some sand and grit,' advises Julian Palphramand, head of plants at British Garden Centres. 'This will improve soil fertility, aeration, drainage, and moisture retention.'

Aim to apply around 5kg per square metre and work into the soil by digging. This is labour-intensive but you will quickly see the results.

2. Mulching

Mulching with bark chips or even a thick layer of straw or grass clippings will prove very beneficial to improve clay soil for gardening – especially if used in conjunction with other methods. In the short term, the mulch will help the soil retain moisture, preventing the clay from drying out, becoming hard and cracking. Secondly, as the mulch decays, it will help break down the clay further.

An added benefit of mulch is that it can serve as a barrier to get rid of slugs, too.

3. Grow green manure

If you want a low-effort approach to breaking up clay soil, try growing green manure. 'Green manure is a crop that is grown mainly to benefit the soil rather than for food or ornament,' explains experts at greenmanure.co.uk.

Green manurers that is particularly suited to improve clay soil for gardening include Field Beans, Red Clover and Forage Rye. These are planted in early autumn, allowed to grow and work their magic over winter and are then cut down before flowering, being dug into the soil or left as mulch.

Green manure also has the added benefit of providing food and habitats for pollinators, making it a great addition to wildlife garden ideas too.

4. Use a clay breaker

Commercially available clay breakers are – for the most part – comprised of horticultural gypsum and will break up the heavy clay particles. 'To use, dig the soil over roughly and apply 200g per square metre. Leave for one month after application, before re-working the soil,' says Nick Worthington from Vitax Garden World.

'Autumn is by far the best time to work an area as it maximises the surface area exposed to frost, airflow and some moisture which all help break the clay up.'

Clay breaker can also be used as an autumn top dressing on lawns to improve drainage in a clay soil lawn.

5. Plant potatoes, turnips or beetroot

Plants with tuberous roots – such as potatoes, turnips and beetroot – are a great way to improve clay soil for gardening as their large roots grow into and break up the clay.

Plus they reward you with a delicious crop at the end of the season. Learn how to grow potatoes or how to grow beetroot for the greatest chance of success.

6. Fertiliser with wood ash

Wood ash is a great fertiliser – high in potassium, phosphorus, and magnesium. However, it is also good for breaking up heavy clay soil. You can use it as a top dressing or dig into the soil.

If you've invested in firepit ideas, then you'll be excited to learn that you can use fire pit ash in the garden as a free way to improve clay soil for gardening. However, it's worth noting that using wood ash will quickly raise the pH of the soil so shouldn't be used around acid-loving plants

7. Break up the soil with grit

'For heavy, clay soil dig in some horticultural grit – such as Westland's Potting Grit from Amazon – to improve drainage,' advises Jekka McVicar VMH of Jekka’s Herb Farm. Add the grit to the soil and turn it over. The grit particles then create air holes in the soil so that water can be absorbed more easily.

Horticultural sand is also useful if you're hoping to plant bulbs in clay soil. 'Add horticultural sand at the bottom of the planting hole. If you have lots of bulbs, work the soil beforehand and use a bulb planter,' advises garden expert Leigh Clapp.

FAQs

What plants are good for clay soil?

Look for flood proof plants or those that enjoy moist environments. These include:

• Rubeckia
• Echinacea
• Hostas
• Foxgloves
• Geranium
• Hydrangea
• Buddleia
• Anemone
• Sedum
• Viburum
• Roses
• Hellebores

How do you improve soil that has a lot of clay?

The best way to improve soil that has a lot of clay is to incorporate organic matter, manure or mulch as this will help break up the clay particles, help water drain and prevent the soil from cracking.