Improving your garden soil benefits your plants and your well-being.
Soil is a magical blend of organic matter, minerals and organisms that support all living plants. It anchors plants into the soil, feeds them and harbours a fascinating ecosystem that creates a healthy growing environment.
But, would you be surprised to learn that improving soil is not just essential for plant health but good for us, too?
Recent research from Bristol University and the University College London discovered that friendly bacteria found in soil activated the happy hormone, serotonin, in laboratory mice.
Dr Chris Lowry from Bristol University said: “These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health. They also leave us wondering if we shouldn’t all be spending more time playing in the dirt.”
The good news is we can officially scrabble about in the dirt! So, whilst we’re at it, let’s look at why and how to improve soil quality to grow gorgeous healthy plants.
Why should I improve my soil?
Good question. It’s just dirt, right?
You’ve all heard the phrase ‘feed the soil, not the plant,’ but did you ever consider why?
In a nutshell, plants constantly use up available nutrients so boosting your soil keeps it packed with vital minerals, improves soil structure and moisture retention, and revamps flowering and foliage displays. Not only that, it all cuts down on the gardening grunt such as watering, digging or adding synthetic fertilisers and helps plants fight pests and diseases.
Let’s dive into the science for a minute, but don’t get too hung up on it; it’s useful to know because some plants struggle to survive in certain soils. For example, azaleas, rhododendrons, heathers and blueberries all love acid soil so if you have clay soil, it stands to reason they’re going to sulk and there’s nothing worse than a mean plant. It’s always better to match suitable plants to your soil type.
Essentially, there are five types of soil: clay, chalk, loam, sand, and silt. They all have varying degrees of acidity or alkalinity, (known as pH).
Any soil with a pH of 7.0 is neutral, above 7.0 is alkaline and acid soil generally has a pH of less than 7.0.
Different soils provide different growing conditions for your plants and each has its pros and cons. Let’s look at how to improve soil for gardening, sometimes called soil conditioning, and how to put nutrients back into the soil by minimising the negatives and boosting the positives.
How to measure soil pH
The first job is identifying what type of soil you have. One of the easiest ways is using soil testing kits that measure your soil pH, which are widely available from garden centres and online.
Great. So now you know what type of garden soil you have, we can focus on how to improve it. Adding homemade compost, organic matter and well-rotted manure is the best way to improve your soil and replace depleted nourishment.
The good news is clay soil allows you to grow some of the widest variety of plants, trees and shrubs. Hurrah! Clay tends to be alkaline and is loaded with essential plant nutrients. California lilac, (ceanothus) or Magnolia loves clay soil, and so do hydrangea, roses, and lilac Madame Lemoine is a perfumed gem.
The downside is that it’s back-breaking to dig, bakes hard in summer, is sticky, lumpy and waterlogged in winter which prevents plants from accessing vital nourishment and they can get bogged down in wet weather.
How to improve clay soil
Adding lots of homemade compost or well-rotted farmyard manure is a cheap and easy way to boost soil structure. Make sure it’s black as your hat and odourless – otherwise, it can scorch your plants.
Adding organic matter to your soil improves the structure allowing plants easy access to nutrients, improves water retention and drainage so plants don’t get waterlogged, and attracts worms and other beneficial insects that play a major role in continually improving soil health. You can find out more about watering here.
You need only do it every 2-3 years and it will keep the plant larder fully stocked with no need for extra fertiliser or additives.
Just spread a thick layer about 2.5cm deep over your borders or around the base of individual plants as needed in winter or early spring. Or, if you’re feeling energetic, you can dig it in.
Chalk soils tend to be thin and stony. It struggles to hold onto nutrients and water, so dries out quickly in summer. You can imagine that it dramatically ups the watering hours during the hot summer months and worse still, heavy watering also washes away vital nourishment.
Chalk soils tend to be alkaline so avoid growing acid-loving plants such as camellias, otherwise, you’ll find foliage turns yellow on chalky soils because plants just can’t absorb sufficient nutrients. Instead, plump for smouldering purple or fresh leafy green beech, alder, golden-flowered berberis or smart Portuguese laurel. Don’t forget, there’s a dizzying selection of gorgeous lavender to choose from, too.
How to improve chalky soils
Adding homemade compost or well-rotted farmyard manure is a cost-effective way to boost soil structure. Make sure it’s dark and has no smell – if it isn’t rotted down sufficiently, it can scorch roots and leaves.
Again, adding organic matter to chalky soil improves the structure, lets air travel through, allows plants to access essential nutrients, improves its moisture retention and drainage and attracts beneficial insects and worms that play a key role in supplementing soil health.
You’ll probably need to do it once a year on chalky soils because nutrients are flushed out so quickly. But on the plus side, adding organic matter keeps your plants in good health and cuts down the hours spent on your watering regime, since soil can hold on to water for longer.
Dig it in or spread a thick layer about 2.5cm deep over your borders or around individual plants in winter or early spring and save the backache by letting the frost break it down for you.
If loam was a car, it would be a Ferrari!
Loam soil is easily the best soil a gardener can have, rich in nutrients, crumbly in texture, lets roots fix easily, holds on to moisture, is easy to dig and gives plants all the goodies they need. You can grow just about anything on loam, trees, shrubs and beautiful perennials.
How to improve loam soil
Despite its impressive credentials, you’ll still need to replenish the soil larder to keep your loam in tip-top shape, so consider adding mushroom fertiliser, compost or well-rotted manure to loam soil every two to three years.
Spread a generous layer about 2.5cm deep over your borders or around individual plants as needed in winter or early spring.
Sandy soil is notoriously poor and often known as hungry soil. It’s fast-draining so doesn’t hold onto water, and lacks essential plant nutrients.
On the bright side, it’s light and makes digging a breeze. It tends to be acidic, but how to enrich poor soil is relatively easy, although you’ll need to be consistent and do it regularly. Go for plants that can cope with poor soil such as lavender, grasses, mock orange and verbena.
How to improve sandy soil
Conditioning soil is an annual job for sandy soil gardeners but it pays huge dividends by improving plant displays and cutting down your workload in the long term. Go for well-rotted manure or homemade compost spread over borders about 2.5cm thick in winter or early spring.
Those of you with silty soil will know it’s fertile and hangs onto moisture but is easily compacted by treading over it or using hefty garden machinery such as lawnmowers.
Silty soil gardeners have fewer improvements, although adding a soil conditioner or organic matter every couple of years keeps things balanced and improves plant health and flowering displays, not to mention producing no end of tasty vegetables. Choose plants including mahonia, hardy geraniums, berberis and the seductive fiery stems of dogwood.
The benefits of mycorrhizas
We should just touch on mycorrhizas because they’re increasingly recognised as bringing vital benefits to plant roots and helping them establish.
Mycorrhizae are beneficial fungi that when sprinkled at the base of plants act as a turbo-charged booster, helping roots expand their capacity to absorb water and nutrients more effectively. It also helps reduce the effects of drought and increases plants’ defences against root disease. It’s easy to use and we recommend Rootgrow, an all-natural product that is hugely beneficial to plant roots as well as the surrounding soil.