If you are planning on a complete renovation of your garden, or even just a small portion of it, the chances are you are going to be planting new and established plants, seeds or vegetables. You are probably aware that you are going to have to check the composition of your existing soil in order to get the best out of your new plants and there is the likelihood that the soil you have in the garden is not going to be suitable for growing what you want and you will need to import some new topsoil.

There are four main areas you should be considering when embarking on any landscaping project; soil type, soil pH levels, soil improvers and the best plants to suit your soil type and pH.

The composition and structure of topsoil varies according to where it is collected and is constantly under the influence of its environment. Each type of topsoil has a unique mixture of earth, organic materials and soil nutrients. Different geology, topography, and weather conditions mean each of us has a unique mixture of minerals, organic matter and organisms in our patch. That said, your soil will share similar characteristics with neighbouring gardens and will reflect the general makeup of soils in the local area.

Before you embark on your garden project, it’s crucial to find out what type of soil you have in your garden. Soil is made up of different material particles and the soil type is determined by the most abundant type of particle.

Soil Types

Clay Soil

Clay soil is sticky, smooth and heavy when wet and contains at least 25% clay. It’s easily rolled into a ball shape in your hand. It retains a lot of water resulting in poor drainage and is slow to warm up in spring delaying plant growth.

Solution: Add plenty of organic matter to break up the solid structure. It will need a lot of work but if you persist the clay will become easier to manage. On the plus side, it’s richer in nutrients than some other soils.

Sandy Soil

Sandy soil, which is more common in coastal areas, is dry and gritty with lots of coarse sand particles. It won’t stick together to form a ball and due to the high concentration of sand, water drains too quickly. It’s quick to warm up in spring, and it’s easy to cultivate.

Solution: Add plenty of organic matter and fertiliser to give the soil a nutrient boost.

Silty Soil

Silty soil has a silky soapy feel and is made up of sand and clay properties. The soil can be squeezed into a small sausage shape and is easily compacted. It suffers from poor draining and is not very common. However, it’s rich in nutrients and holds more water than sandy soil.

Solution: Add organic matter to bind the fine particles and it will become a very good fertile soil.

 

Chalky Soil

Chalky soil is stony, pale, and full of lumps of chalk. It’s tricky to dig due to its high stone content. It’s low in nutrients and drains easily, however it can get very dry in summer. It often has a high lime content which means it’s alkaline is nature.

Solution: Add plenty of organic matter and fertiliser to boost it’s nutrient content. There’s not much you can do to remedy chalky soil, so pick plants which thrive in alkaline conditions. Avoid ericaceous (acid loving) plants such as heather and rhododendrons.

Peaty Soil

Peaty soil is high in organic matter but low in nutrients. It is dark brown or black in colour, soft and spongy in texture. It’s easily compressed due to its high water content.  Although peat soil tends to be heavily saturated with water, once drained, it turns into a good growing medium especially for acid loving plants. In the summer though peat can be very dry and can actually become a fire hazard!

Solution: Drainage channels may need to be dug for soils with high peat content. Peat soil is great for growth when blended with rich organic matter, compost, and lime to reduce the acidity. You can also use soil amendments such as glacial rock dust to raise pH in acidic soils like this.

Loamy Soil

A loamy soil is a gardener’s best friend! Partly smooth and gritty when made into a ball and will crumble easily. Good balance of sand, silt and clay. Great structure and drainage whilst holding moisture well. High in nutrients and easy to cultivate. Creates an ideal growing environment for many species of plants and flowers. The sand content keeps the loam ‘open’ so air, moisture and sunlight can reach the plants, while the clay and silt content slows down drainage and evaporation, keeping water and nutrients in place. Loam warms up early in the spring, won’t dry out in the summer and still drains well in heavy rain, making it the perfect soil for year-round planting. This type of soil is dark rich in colour, lightweight and friable.

Solution: Whilst loamy soils can vary in their specific makeup, they’re usually easy to bring into balance by using simple additives. Compost or mulch can make up for any minor imperfections in the soil content, creating a versatile planting base for virtually any type of plant. Just add organic matter every year to give a nutrient boost.

Soil PH levels

When designing and planting your garden, you need to know whether the soil is acid or alkaline, as different plants thrive in different soils. The soil pH is a number that describes how acid or alkaline your soil is.

The acidity or alkalinity of a substance is measured in pH units, a scale running from 0 to 14.

  • A pH of 7.0 is considered neutral – this is neither acid or alkaline.
  • An acid soil has a pH value below 7.0
  • An alkaline soil has a pH value above 7.0

As an example: very sandy soils tend to be more acidic whereas soils with a high calcium content such as chalky soils are very alkaline.

A good quality topsoil should have a pH value of between 5.5 and 8.5 which is mildly acidic to slightly alkaline and ensures the plants are able to take up the nutrients in the ground. Most plants are able to cope with quite a range of pH values, but if the ground is either too acidic or too alkaline then they will encounter problems.

Having said that there are certain plants which prefer soil that is more extreme. Vines like honeysuckle and clematis thrive in alkaline soil. A wide range of flowering and ornamental plants are perfectly suited to these soil conditions as well such as lily’s, bluebells and daisy’s. Acid-loving plants include azaleas, rhododendrons, hydrangeas and daffodils.

It is especially worth checking soil pH before designing or planting a new garden, making vegetable plots, planting fruit, where yellowing of foliage occurs or when growth is disappointing. You can test the pH of your own soil using a DIY soil testing kit or have it carried out by a soil-testing laboratory. Testing can be done at any time, but if carried out within three months of adding lime, fertiliser or organic matter, the test may give misleading results.

You can only make a minor change to your pH level and it’s easier to raise the pH to make it more alkaline than lower it.

pH 7 or higher = Alkaline soil.  You may need to add acidifer such as sulphur chips.

pH 6.1-7 = Neutral. This is ideal soil! Bacteria and nutrients are most effective at this level.

pH 5.1 – 6 = Acidic soil. This is perfect for ericaceous (acid loving) plants. Add lime, such as slaked or ground lime (not builder’s lime).

pH 4.0 = Highly acidic soil. This may limit plant growth and extract nutrients from the soil.

Soil Improvers

If your soil is not ideal, all is not lost! You can improve it with organic matter.  Simply add a soil improver such as a shop-bought or homemade compost, bark chips, ash, special soil conditioners and manure.

Bark chips don’t add nutrients but you can dig bark into heavy soils every year to improve the structure and drainage. This may acidify your soil slightly.

Once you have sourced your soil improver, dig it into your soil at a rate of half a wheelbarrow load per square metre and dig your soil over to a least a spade’s depth. Don’t worry if you’ve already planted your garden, you can just gently loosen the soil around the plants with a trowel and add organic matter over the top in early spring. Better known as mulching, it will improve the soil condition. Little and often is the key and over time the soil will improve greatly with regular applications of organic matter.

Working with what you’ve got

If you’d like to work with what you’ve already got, here are some plants which thrive in certain soil types.

Clay soil
Bluebells, roses, foxgloves, hosta, sedum, sorbus, peonies, helenium, aster, weigela, chaenomeles, labernum, berberis, hydrangea, abeli

Sandy soil
Daphne, tulips, cytisus, hibiscus, verbascum, eucalyptus, juniper, pine, buddleia, lavender, allium, iris, poppy, wallflower, wisteria, euphorbia, euonymous, ceanothus

Silty soil
Mahonia, phormium, kerria, malus, bergenia, pyracantha, nicotania alata (tobacco plant).

Acidic soil
Crinodendron, hamamelis, heather, camellia, rhododendron, pieris, hydrangea, azalea, magnolia, blueberries, witch hazel

Alkaline soil
Lilac, mint, madonna lily, dinathus, philadelphus, sedum, thyme, verbascum, carnation, wallflower, delphinium, buddleja, wisteria, duetzia, Helenium, daffodils and vegetables especially broccoli and cabbage