The proposed ban on using peat on private gardens and allotments is in danger of being weakened as opponents argue it is more difficult to grow carnivorous plants and other flowers without the environmentally damaging compost products.
However, the Royal Horticultural Society (RHS) is hoping a successful experiment in which carnivorous plants grown peat-free outshone those grown in peat will convince ministers not to water down the ban.
Peat compost is bad for the environment because harvesting the nutrient-rich, partially decayed organic matter releases carbon into the atmosphere. Peat is one of the UK’s most important carbon sinks, and many of the country’s peatlands are in a poor state, with some emitting carbon rather than storing it.
The government has already delayed the ban, which was supposed to have been introduced for the horticulture industry in 2024, to 2030. There are now fears certain plant types will be grown in peat past that deadline because of exceptions to the rule.
Scientists at the horticultural charity have successfully grown two popular varieties of carnivorous pitcher plants in five different peat-free growing media, all judged to be superior to the control plants grown in 100% peat. These pitcher plants were thought to be among the hardest to grow peat-free as they are found growing in peatlands in the wild.
RHS scientists, led by Dr Marc Redmile-Gordon, worked with Sean Higgs of Floralive, a carnivorous plant nursery that has grown peat-free since 1990, and grew a Sarracenia leucophylla hybrid and a subspecies of Sarracenia purpurea. These plants have ornate pipes, or pitchers, formed from folded leaves, which they use to trap their animal prey, delivering them supplementary nutrients not typically provided by the nutrient-poor soils in which they grow.
The plants were grown under identical conditions in six different growing-media combinations, including mixes of sustainably grown sphagnum moss, pine bark and acidified biochar, commercially formulated peat-free media produced by Floralive and a control group grown in peat.
The Chelsea flower show judge and carnivorous plant expert Roy Cheek joined Mike King, the national collection holder for Sarracenias, to judge the plants based on their growth and aspects of their appearance.
They judged plants grown in blends of sphagnum and other organic materials to be vastly superior to those grown in peat. Cheek was especially impressed by the array of colours in the Sarracenia grown without peat.
Prof Alistair Griffiths, the RHS’s director of science, said: “It is very exciting to see the results from the judging clearly demonstrating that the plants grown in peat were inferior to those grown in alternatives, and that Sarracenia can be grown to the highest standard without peat.
“Moving away from peat in horticulture has a key role in meeting net zero through protecting and restoring peatlands, turning them from carbon sources to carbon sinks and preventing further loss of these vital habitats. Our research comes at a critical point in the UK’s response to the climate crisis, when it is more important than ever that all possible reductions in emissions are made.”
The scientists will share the contents of the peat-free media mixes with the public so they can create their own mixes of the peat alternatives. Some of the peat-free Sarracenia will be planted at RHS Garden Wisley, while others will be available to buy at the Wisley garden centre.
The team plans to look at growing other popular carnivorous plants without peat, including Venus flytraps (Dionaea muscipula), as well as testing a wider range of ingredient mixes and growing protocols to aid the UK horticulture industry in transitioning profitably away from peat.
A government spokesperson confirmed that technical exemptions for some plants were being considered.
They added: “We have repeatedly stated that if the voluntary targets to phase out the horticultural use of peat, set in 2011, were not successful then we would need to legislate. Our peatlands are our largest carbon store as well as a uniquely valuable habitat. Our approach has sought to achieve our commitments to restore our peatlands while acknowledging the challenges faced by the horticulture sector in transitioning over the last 10 years.
“We believe that a ban in the amateur sector for 2024, which accounts for 70% of use, is still the right approach. Furthermore, we feel that a phased approach for the professional sector with some exemptions from 2026 and a full ban from 2030, is achievable given the number of peat alternatives available and the period of time permitted for the sector to adjust.”
