Kew's compost heap is one of the biggest non-commercial heaps in Europe.
Kew makes 4,000 cubic metres of mulch a year. Not having to buy in mulch or take waste to landfill sites saves around £500,000 a year.
About Kew's compost heap
Kew’s compost heap lies south of the Lake in an area called the Stable Yard. This is off-limits to visitors but there is a viewing platform in the Pinetum from where the compost-making process can be observed.
All garden waste is taken to the yard and placed on one of two huge mounds, one containing woody material and the other herbaceous cuttings. Both piles are screened, shredded and mixed with generous helpings of manure from the Royal Horse Artillery Stables in St John's Wood.
The decomposing material heats up naturally to 60°C and rapidly rots down. Staff occasionally sprinkle it with water and turn it by JCB but no other action is required. Eight weeks after arriving in the yard it is ready to go back on the garden as mulch or to enrich the plants it came from.
Kew’s production of mulch contributes towards maintaining its ISO 14001 accreditation (awarded in 2005, Kew became the first World Heritage Site to gain the ISO14001 accreditation for sustainability). This is a standard for sustainability, and covers areas of Kew’s operations such as water use, recycling and carbon emissions.
Peat-free compost at Kew
Peat bogs are important habitats and valuable stores of the greenhouse gas carbon dioxide. However the use of peat, primarily as a potting compost, has damaged or destroyed 94% of the the UK’s peat bogs. Kew took the decision to stop using peat in 1989, except for carnivorous plants that cannot be grown in any other medium. It now uses peat substitute for potting composts and makes home-grown mulches at Kew and Wakehurst, using waste plant matter from the Gardens.
Things to look out for
Kew’s resident peacocks seem to like the warmth of the compost heaps and can often be seen perched on top of them.