Arboriculture firms have the opportunity to bid for a contract covering tree surgery work in English Heritage's London region.
The five-year contract, which will begin in April and could be extended for up to a further three years, will include work at not only Down House in Kent but also Coombe Conduit, Eltham Palace, Jewel Tower, Kenwood House, Marble Hill House and Rangers House.
Among the 8,000 trees that feature in the sites are a significant number of veteran trees, explained English Heritage regional landscape manager Brian Clarke.
"It might be particularly interesting to firms specialising in historic gardens and landscapes," he said. "We are involved in moves to use different techniques, such as coronet cutting, so we are looking for those sorts of methods."
A distinctive feature of Down House is Darwin's Sandwalk, or "thinking path", which was created in 1846 when a 0.6ha area of land was fenced off and planted out with native trees and a circular path dressed with sandy gravel around the edge.
Darwin would take his daily walk a number of times around the path counting the laps with flints piled at the beginning of the circuit.
Previous contract holder Connick Tree Care carried out work across the sites for the past five years. The deadline for receipt of tenders or requests to participate in the work is 17 February.
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