Pots without peat: National Trust and RHS trials confirm success for peat alternatives
The National Trust and the Royal Horticultural Society has announced the results of a series of year-long trials that bring good news for environmentally-conscious gardeners.
Despite continued concerns about the impact of global peat extraction for use in horticulture on lowland peat bogs and their fragile habitats, the vast majority of the gardening public buys multi-purpose compost. This is peat based unless labelled otherwise, and a large proportion of this is used to fill patio pots and containers.
In spring 2004, in response to this need to demonstrate effective peat alternatives for container-grown and ericaceous (acid-loving) plants, the National Trust and the RHS set up a series of joint trials and demonstrations in a selection of their gardens throughout the UK.
Eight famous gardens participated in the trials: four RHS gardens (Wisley in Surrey, Hyde Hall in Essex, Harlow Carr in North Yorkshire, Rosemoor in Devon) and four National Trust gardens (Hidcote in Gloucestershire, Nymans in West Sussex, Knightshayes in Devon and Lanhydrock in Cornwall). Each grew a wide range of plants suitable for container planting in peat-free and peat-reduced mixes.
Over 15 plant varieties were grown successfully and even where some in the peat control mix started off stronger, the peat-free examples caught up and produced better plants later in the trial. All the peat-free mixes were bark and wood-fibre based. The peat-reduced mix was 50% peat. Many gardens also used their own mix as well.
Five of the gardens were also involved in trials of ericaceous shrubs, such as rhododendron, camellia and azalea, which are recognised as being more difficult to grow in peat alternatives. As expected, the plant performance was more variable but nevertheless, gardeners with experience of growing ericaceous shrubs obtained some good results. The peat-reduced mix proved comparable and in several cases better than the peat-based one.
While all the gardeners involved in the project were experienced growers, the plants were not afforded any special attention and were treated the same way as any of the other plants being grown and managed in the garden.
The impact of peat extraction on lowland peat bogs
94% of the UK's lowland peat bog has been lost and less than 5,000 hectares of lowland peat bog now remain in prime condition in the UK. Most of the loss has historically been due to agriculture and forestry with gardening ranking third until the 1950s. Since the 1950s the biggest use of peat has been in horticulture.
Regeneration of a damaged bog towards its original diversity of wildlife is expected to take hundreds of years, if achievable at all, while historic features are lost forever. Approximately 2,250 wetland archaeological sites have been destroyed out right.
Lowland peat bogs are home to some of our rarest plant and animal species. They are also the final resting places for 'bog bodies' complete with their everyday objects, such as leather purses and flint tools. Ancient wooden trackways that were repeatedly re-made as the bog surface grew, remain as evidence of our earliest 'roads'. Such artefacts are at risk of being 'harvested' along with peat and sold in bags of compost to supply the horticultural trade.
The amateur gardening market accounted for a 54% increase in the use of peat between 1993 and 1999. Virtually all of the rest is used to grow plants, most of which are sold to the public in garden centres.
There are two Government targets for peat replacement. A requirement for 40% of the materials used in growing media and soil improvers to be of peat alternatives by 2005 was introduced in 1995. This was extended to 90% of materials in growing media and soil improvers to be of non-peat by 2010 in the UK Biodiversity Action Plan in 1999. The last Government survey of peat use in 2001 showed that 37% of these materials were of peat alternatives.
From the 1950s to 1970s, MAFF funded millions of pounds worth of research and development to help the horticultural industry move from traditional loam-based substrates to peat-based ones. DEFRA is currently funding some research into using recycled materials for use as peat alternatives, largely via the Waste and Resources Action Programme. WRAP has been formulating and testing growing media containing recycled and composted materials, progressing some work towards a compost specification for use in growing media and helping to promote the use of recycled/composted materials as an alternative to peat. This is a useful contribution, but much more needs to be done to gain industry-wide knowledge, supply and use of the range of materials that can be used as effective peat replacements.
The RHS produces an information leaflet Peat and the Gardener, which can be downloaded from the RHS website at www.rhs.org.uk/Learning/research/conservation_and_environment_peat.asp or by post by sending an A4 SAE, marked with the name of the leaflet, to AW Mailing, PO Box 38, Ashford, Kent TN25 6PR.
Further information and advice can be found on the RHS website at www.rhs.org.uk/Learning/research/horticultural_themes/peat.asp
The National Trust and the Royal Horticultural Society policies on peat
Both charities:
Share public concern about the impact that global peat extraction for use in horticulture is having on lowland peat bog archaeology and wildlife habitats and fully endorse the need for strong protection of peat bog habitats.
Support and encourage studies into the use of peat alternatives, believing that while viable alternatives are currently available for the majority of growing media uses, there is a need for further research and development into sustainable peat replacements.
Consider the purchase of peat to be unacceptable for the primary use of soil incorporation and ground mulching.
Would like all retail outlets that stock peat for horticultural purposes to offer gardeners the choice of peat-free alternatives from sustainable sources.
Would like clearer labelling of growing media, their composition and instructions for use, enabling gardeners to make an informed choice.
The National Trust and RHS do not use peat as a soil improver or mulch in their gardens.
RHS
The RHS prohibits the use of peat for staging purposes at its flower shows.
Plant centres run by RHS Enterprises will stock alternative, peat-free products which are clearly identifiable and at a competitive price.
National Trust
All plants bought and sold at National Trust properties are grown in peat-free growing media, with the exception at the present time of ericaceous plants.
All 200 National Trust gardens are now managed peat free, except where there is as yet no alternative to the use of peat to maintain ericaceous plants.