Peat-free growing media

For decades, peat-based potting composts have been used to raise and grow-on plants. Due to the concerns about the damage done to the environment, gardeners are now reaching for peat-free or reduced-peat products as an alternative.

Using peat-free compost for potting. Credit:RHS/Advisory.

Quick facts

  • Peat-free compost can perform very well
  • Buy the right compost for the job by reading the label
  • Homemade mixes are best avoided for seed sowing
  • 'Environmentally friendly', 'compost' and 'organic' compost aren't always peat-free

Why use peat free-growing media

Peat is primarily sourced from lowland raised bogs – an increasingly rare habitat in the UK and across Europe. In recent years, the need to conserve this diminishing natural resource has been recognised, as well as the flora and fauna that depend on it. Peat bogs are also an important carbon sink: destroying them to make garden compost contributes to climate change.

Compost manufacturers have responded to this by producing an ever-increasing range of peat-free growing media to grow plants in.

Peat-free and reduced-peat compost choices

Peat-free potting composts contain mixtures of organic materials – e.g. composted bark, coir (coconut fibre), woodfibre and green compost – mixed with inorganic materials such as grit, sharp sand, rock wool and perlite. A mix of coarse and fine particles is needed to create a balanced compost containing enough water and air, which are essential for root growth.

Completely peat-free media are said to be the best choice for the environment, but product consistency can be problematic, so many brands also offer ‘reduced-peat’ choices, blending into the formulation up to 50 percent non-peat materials. Manufacturers are continuously improving the quality of the blends.

Preferably, choose peat-free compost with good on-label information. Read and follow the instructions on the packaging about the suitability of the mix for particular purposes.

Peat-free brands often recommend specific fertilisers for use with their compost: this is not a marketing ploy, as different formulations have different balances of nutrients. Use either the recommended product or one with a similar nutrient balance – compare fertilisers by checking the NPK ratio and the trace-element content quoted on the packaging.

Materials used in peat-free compost

Most peat-free composts contain wood-based materials as their primary ingredient, e.g. woodfibre, composted bark, sawdust, wood or paper waste. Wood-based mixes can be tailored to the requirements of most plants as they have excellent drainage properties as well as a low pH.

Coconut fibre or ‘coir’ is mainly imported from Sri Lanka. Coir is a waste product. It has excellent natural water-holding ability and a sufficient mix of fine and coarse fibres to hold air in its pore spaces, making it a good growing medium. It does not hold nutrients well, however. The environmental credentials of coir-based products are questioned due to the distance they must be transported to the UK, but this is balanced out by the fact that it is a genuine waste material.

Green Compost
Many Local Authorities and private companies are collecting and composting green waste, the resultant green compost tends to have a high nutrient content and a high pH making it an excellent soil improver or mulch. There is an industry standard (British Standards Institution PAS100) for green compost that enforces consistent and regulated processing in order to encourage its use in potting composts. Due to its high pH and high levels of nutrients, green compost tends to be mixed with other materials to make potting compost – it is usually no more than 30 per cent of the overall product.

Locally Available Materials
Research is ongoing into a number of materials that, while locally available, may be useful ingredients in blended products, e.g arable straw waste, wool waste, carpet waste and paper and cardboard production waste.

Gardeners can mix well-rotted, home-made compost, leafmould and inorganic materials (loam and sand) to make their own peat-free growing media, but results tend to be variable. It is difficult to standardise pH, moisture retention and available nutrients, and to ensure that the final mix is weed-free. Home-made potting media are best avoided for seed sowing (because of the potential for them to contain fungal pathogens that can harm seedlings or cause damping off).

Product choice

For non-ericaceous plants most of the major manufacturers produce peat-free products, including Bulrush, J Arthur Bowers, Dalefoot, Scotts, SylvaGrow and Westland.

The choice for ericaceous plants is more limited, but gardeners should look for the recently-introduced Vital Earth Ericaceous Peat-Free Compost and SylvaGrow Ericaceous. Alternatively, most of the major manufacturers produce peat-reduced brands, which should be suitable.

What to check when buying peat-free products

  • If the bag doesn't say peat-free then it most likely isn't
  • Wording such as 'environmentally friendly', 'compost' and 'organic' can often confuse gardeners into thinking they are buying peat-free products, but they do not infer this
  • A good quality peat-free growing media is usually a little more expensive. The price does tend to reflect quality.
  • Check the label on the bag to see if it is recommended for particular plant groups (such as seed sowing or growing bedding plants)
  • Read and follow any advice offered on the label of peat-free products as many need slightly different treatment (when caring for the plants growing in them) to peat. Pay particular attention to watering and feeding requirements as these do tend to differ

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