Peat alternatives are now being developed using materials such as bark, wood fibre, coir, biosolids, bracken and green compost. Due to the inherent differences between media, product development will take time and gardeners have to be aware that there are different management requirements associated with all of the different products. The development of growing media now focuses on specific purposes, like propagation.
Several decades of research went into the perfection of horticultural techniques using growing composts with high grade peat as the sole or major ingredient. Similarly, it will take time to adjust to using peat alternatives.
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 (e.g. forestry, composting etc). The environmental impact of transport is also reduced.
Some plant groups (eg ericaceous plants), and growing media formulations (eg 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 demonstrations
The RHS has undertaken a number of comparative trials at its 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 the majority of 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. Some products have been found to be plant specific and gardeners should not assume that all plants will perform similarly. Other products have been seen to either promote or delay plant development, thus 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 they are best suited to, as well as the watering and feeding requirements.
In took several decades for peat to be fully accepted by horticulturalists. Peat alternatives probably offer a greater challenge in terms of both product manufacture and plant management but peat-free products are improving with good products already existing.
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.