The Royal Horticultural Society (RHS) has successfully grown two commercially favoured varieties of carnivorous pitcher plants using five different peat-free growing media. All final specimens were judged to be of superior quality to that of the control plants grown in 100% peat.
Carnivorous plants were considered to be ‘one of the most difficult’ plant groups to transition to peat-free with several variants can be found growing naturally in peatland habitats.
The pitcher plants used were a Sarracenia leucophylla hybrid and subspecies of Sarracenia purpurea1, known for ensnaring their animal prey through ornate pipes (or pitchers), providing them the nutrients not naturally found in the nutrient-poor soils of their typical habitat.
Photo credit to the RHS.
Sarracenia plants established from peat-free propagules were grown under identical conditions in six different growing media combinations, including mixes of sustainably-grown sphagnum moss, pine bark and acidified biochar, commrcially formulated peat-free media produced by Floralive and a control group grown in peat.
The plants grown in blends of sphagnum and other organic materials were all judged to be of superior quality to those grown in peat, with the two cultivars performing best with different peat-free medias.
Professor Alistair Griffiths, RHS director of science, says: “This research is a positive step forwards in delivering the RHS Sustainability Climate Positive Target and in the RHS transitioning to peat free by the end of 2025.
“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 RHS banned the sale of peat containing media in 2018 and are at present 98% eat-free with projections for 100% by the end of 2025, following the establishment of a £1m co-funded five-year peat-free research project.
Following the success of the Sarracenia experiment, the RHS will now be actioning plans to grow other commercially popular carnivorous plants without peats, 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 selection of the peat-free Sarracenia will be planted out at RHS Garden Wisley, with others set to be made available for purchase.
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