Alternatives to peat

Peat alternatives are now being developed using materials such as bark, wood fibre, coir (pictured), biosolids, bracken and green compost. Several decades of research went into perfecting horticultural techniques using composts containing peat, so it will take time for the same thing to happen with the peat alternatives. The important thing is that gardeners are aware that the peat alternatives all need to be managed differently.

Some of the alternatives are made from locally collected waste material, which is processed into a growing media product. By supporting the development of local, environmentally friendly peat alternatives - as an alternative to foreign peat extraction - we are benefiting a number of UK industries (such as forestry and composting). The environmental impact of transport is also reduced.

Some plant groups (such as ericaceous plants) and growing media formulations (including multi-purpose compost) offer a greater challenge to the development of peat alternatives. Many alternatives are alkaline, making them unsuitable for ericaceous plants that require an acidic medium. The differing nutrient concentrations also make it difficult to develop a multi-purpose compost suitable for the wide range of plants traditionally grown in such products. As an important first step, many growing-media producers have developed mixes containing reduced volumes of peat. The phasing out of peat in this manner should enable manufacturers to maintain the quality of products available.

RHS comparative experiments

We have undertaken a number of comparative trials at our gardens on peat and peat alternatives. A wide selection of materials (including bark, wood fibre, coir, green compost and biosolids) has been assessed for the cultivation of a range of ornamentals and vegetables in different situations. The demonstrations have provided first-hand information on the benefits and challenges of different products, showing that most plants grown in peat alternatives are comparable to those grown in peat.

The demonstrations have also shown that peat alternatives should not be treated in the same way as peat; gardeners should not assume that all plants will perform in the same way. Other products have been seen either to promote or delay plant development, making plant management more complicated. When trying new composts, gardeners should allow a period of familiarisation in order to obtain the best results. Read and follow closely any recommendations offered on the packaging on the type of plants to which they are best suited, as well as the watering and feeding requirements.

It took several decades for peat to be fully accepted by horticulturists. Peat alternatives probably offer a greater challenge both in terms of product manufacture and plant management but peat-free products are improving and good products already exist.

Traditionally peat has also been used for soil improvement and ground mulching but other materials are better suited to these tasks than peat. Peat is never used as a soil improver or mulch in RHS Gardens.

Soil can be improved by incorporating well-rotted animal manures or composted plant remains; both materials can also be used for mulching, along with wood chips, wood shavings, bark and other materials.
 
Further reading
Read RHS advice on peat-free media