Using Top Soil, Potting Compost and Bark Chippings in the Garden

Top soil (or topsoil) as its name implies is the rich layer of soil normally found between 5 and 10 inches from the surface. It is a combination of mineral particles, organic matter, microorganisms, water and air. 

Top soil can be mixed with the existing soil in your garden to improve its quality, or used for the creation of new growing areas such as a new flowerbed or raised bed. In brand new properties it may be necessary to apply top soil to the garden, as the subsoil from the foundations may have been spread over what is now the garden.

When top soil is sold commercially it will have been tested to several British Standards to ensure its quality, consistency and provenance - don't be tempted by adverts for 'cheap top soil', more often than not this will be low grade sub-soil that has come from a building site!

The basic constituent of quality top soil comes from sustainable greenfield or agricultural sites, where it is harvested and then carefully processed to give a consistent product - additives such as sand or lime may be added to balance the consistency or pH of the soil, before it is sieved to remove large stones and other matter.

Before we look at the difference between top soil and compost, we need to clear up the difference between compost and garden compost. Compost or potting compost is a medium that can be used to grow plants in containers or pots. Garden compost is the rotted down matter from a compost heap which is applied to the soil to increase its organic matter - you would never use garden compost in pots or planters.

Compost or potting compost is essentially a high-grade manufactured super soil, containing an exact combination of organic matter, sand and grit, fertilizer and lime. Different brands of compost will have their own unique formulation, and composts for specific uses will have different consistencies. 

For example, seed compost will have a very fine structure to allow seedlings to germinate, whereas a container compost may include water retention ingredients to reduce water loss, or slow release fertilizer to stimulate prolonged growth.

Compost or potting compost will also tend to have a higher nutrient content than top soil, and may have been sterilised to remove any weeds or plant diseases. Hence it is recommended to always use a potting compost for planters or pots where your plants have a limited amount of room to grow.

What is peat-free compost?

Peat is a naturally occurring form of organic matter, formed from decaying plant matter in peat bogs over thousands of years. It was widely used in gardening and in composts until the environmental impact of harvesting peat was recognised.

Hence the use of peat is now being phased out in garden products and will be banned from 2024, and many gardeners already make the decision to choose peat-free products.

Modern composts, such as Westland New Horizon Compost, use sustainable organic matter such as coir in place of peat to produce high quality, high performing potting composts.

Bark chippings are a wonderful organic medium to use in the garden, and have two main uses:

• ornamental bark to cover beds and borders, suppressing weed growth, protecting from frost and reducing water loss (mulching)
• play bark to act as a soft surface around children's play areas

Bark chippings used for mulching flower beds or vegetable gardens tend to be a smaller size than those used for children's play areas, and are usually laid over a weed suppressing membrane on soil to suppress weed growth, and to conserve water.

If you're laying landscape bark on a completely empty bed, then it's simple to cut a cross in the membrane once laid, dig a hole for your plant then replace the membrane and bark. 

To add a layer of mulch to an area that is already planted then the process is slightly more complicated, laying a patchwork of membrane pieces to fill the gaps between plants, then dressing with bark. For sloped areas it's also recommended to use fixing pegs to secure the membrane.