17 Apr 2020

It’s time to go peat-free

Kevin McGinn

The Growing the Future project and the Botanic Garden’s horticulturists have been trying out a variety of peat-free composts. The results are positive all round!

As a gardener, one of the best things you can do for the environment is to abandon the use of peat compost. Healthy plants can be grown without using any peat – the National Botanic Garden of Wales, many other botanic gardens and the National Trust have been fully peat-free for many years.

You may have tried a peat-free compost in the past and were put off, but give them another try. The compost industry has been working hard to develop good sustainable alternatives to peat – the quality and consistency of these products has improved greatly and there is an ever-increasing range.

Why is going peat-free important?

Peatlands are of great importance for the planet. They take thousands of years to form but are being drained and dug out at an alarming rate to produce garden compost.

If you’ve bought a bag of ‘multipurpose compost’ lately, check the bag – it may well contain peat.

Peatlands are an increasingly rare habitat for specialist plants and wildlife like insect-eating sundew plants, fluffy-headed cottongrass, bog mosses (Sphagnum), large heath butterfly and wading birds such as the dunlin. In Wales, one of best places to see this special habitat is Cors Caron National Nature Reserve near Tregaron. Most of the peat used in UK garden compost comes from Ireland or Eastern Europe, where equally special habitats are being destroyed.

Peat is an organic-rich soil that locks away enormous amounts of carbon. Globally, peatlands store more than double the amount of carbon than the world’s forests, but the peat needs to stay in the ground and waterlogged to do this. Draining and digging peat up to use as garden compost allows it to break down with time, releasing carbon dioxide and methane, contributing to climate change.

Peatlands also hold huge volumes of water, so they play an important role in preventing flooding and filtering the water that ends up at our taps.

Fortunately, quality peat-free composts are available, but it can pay to be a savvy shopper.

Peat-free materials

Peat-free composts are usually made from blends of raw materials with different properties. There’s a bit of science involved for the manufacturers as factors like density, drainage, water holding ability, nutrient retentiveness and pH all need to be considered. The most common materials in peat-free compost are:

  • Composted bark: A by-product of the forestry or timber industry. Good for drainage.
  • Coir (coconut shell fibre): A waste product from the coconut industry with a fine texture and a good water holding ability.
  • Wood fibre: A by-product of industry or a new material. Good for drainage and forming an open structure but in high quantities can lock up nitrogen.
  • Composted green waste: Produced from garden and sometimes food waste. A great cheap resource to use as a mulch or to mix with other soil/compost, but high amounts are not good in a potting compost.
  • Other organic materials: These include composted bracken, wool and straw.
  • Inorganic materials: To improve drainage, sand, grit and the minerals perlite and vermiculite are sometimes used. Loam (soil) is sometimes added in small amounts to improve water holding ability or nutrient retention.

Peat-free compost products

We have been trying out a range of peat-free composts available to home growers, all of which have performed well:

  • Pure coir: Available to buy in bags ready to use, or as dry bales or bricks to rehydrate at home. Good for use as a seed compost – although it is low in nutrients, seeds have enough nutrients within them.
  • Dalefoot: Made in the Lake District from composted bracken and sheep’s wool. Bracken is plentiful in the UK and can be a weed to farmers, so trimmings would otherwise go to waste. The wool is said to improve water retention and add a long-term release of nitrogen. Other mixes are available, including for ericaceous (for acid loving) plants.
  • FertileFibre: A coir-based blend with vermiculite, producing a fine texture. Other blends are available, including a seed compost and one with added loam.
  • Martin’s TLC: Worm casts produced at a farm in West Wales, mixed with coir. The worm casts add nutrients that the coir is otherwise lacking.
  • Melcourt SylvaGrow. Melcourt compost is very popular for professional growers and is endorsed by the Royal Horticultural Society. Their product for home growers, SylvaGrow, is made from fine bark, wood fibre and coir. Melcourt produce other growing media, including for ericaceous plants.
  • Westland New Horizon: A reformulated blend, largely of wood fibre and coir.

We have also tried a couple of products available to the trade:

Tips to grow peat-free

As with many things, switching to a new product can take a bit of adjustment. You may find you need water slightly more regularly. However, bark-based mixes can look dry on the surface and have plenty of moisture below, so check with your finger before watering. Plants may also need a little extra feeding.

The coir-based products are generally better for germination as they have a finer texture than blends with a lot of bark or wood fibre.

The price of peat-free compost tends to reflect the quality. The cheapest can contain high amounts of composted green waste and are often best avoided, but they can still be fine if you’re looking to enrich your soil or mix with other products to fill large containers.

To keep costs down, consider whether you really need compost for each job and save your better quality compost for sowing seeds and potting on. Garden soil can be the best medium to use in many cases. If you’re growing wildflowers, herbs and mature perennials in pots or filling raised beds, using at least some garden soil is a good thing.

You could also make your own mixes with garden soil (loam), sand and homemade leaf mould – Garden Organic has produced a good guide. These mixes could include some bought-in compost.

If you have a compost heap, you can also add well-rotted homemade compost to your mixes. Homemade compost is packed full of nutrients, so it’s fantastic to enrich soil in the veg patch or flower borders, or for mixing in with soil to grow nutrient-hungry plants like tomatoes. However, it is too rich for sowing seeds in and may contain fungal pathogens that affect young plants and cuttings.

If you’re a member of a gardening club or community garden, you can keep the cost of peat-free composts down by organising group orders by the pallet. The Peat Free April campaign on Facebook and Twitter has provided information on bulk ordering.

Buyer beware

Be wary of any compost labelled with ‘reduced peat’ as these products contain up to 80% peat. Give the labels a good read before you buy. Organic doesn’t necessarily mean peat-free.

There are composts on the market made from ‘reclaimed peat’. This is peat and leaf mould dredged out from reservoirs by the water industry. The peat they contain is still not sustainable though – if the peatlands were being managed well, peat wouldn’t be eroded and washed into reservoirs, so it is best not to encourage a market for these products.

The plant nursery trade is slowly embracing peat-free growing, but a lot of peat compost is still used, so look out for plants grown without peat. A handy list of peat-free nurseries can be found here.

We are really pleased to have found a range of quality peat-free composts available for home growers. There are many more products on the market and the range is expanding year on year.

Why not experiment yourself to see which works best for you and the plants you grow?Good luck and happy peat-free growing!