Rare orchid discovered thriving on green roofs at Oxford Brookes University

A rare orchid has been discovered flourishing on the green roofs of Oxford Brookes University, forming part of a surprisingly rich ecosystem of more than 100 plant species now established across several of the University’s buildings.

The White Helleborine orchid was recorded for the first time this month during an ongoing plant survey led by Dr Andrew Lack, Senior Lecturer in Environmental Biology. The discovery was made on the roof of the John Henry Brookes Building.

Dr Lack, who has been monitoring the University’s green roofs since 2017, described the find as unexpected.
“That was the find of the day, a totally unexpected orchid that I have not seen there before and is almost confined to the Chilterns within Oxfordshire,” he said. 

The White Helleborine is a shade-loving perennial herb typically found in woodland environments, chalk scrub, abandoned quarries, and occasionally north-facing grassland. It is listed as Vulnerable on the Great Britain Plant Red List, highlighting its conservation significance.

Dr Lack added that while orchids are rare on the roofs, other species have previously stood out: “Until now the real showstopper was the gloriously named Viper’s Bugloss, which is an unusual sight locally. This bright blue-flowered beauty is a hit with the bees and is growing in some quantity across the roofs of the John Henry Brookes Building.”

The green roofs were installed on buildings opened since 2012, including the John Henry Brookes Building, the Colonnade, the Abercrombie extension, and the John Payne Building. They were originally planted with drought-resistant stonecrop (Sedum) species. Over time, their shallow soil substrate has allowed a wide range of additional plants to colonise naturally, transforming them into semi-wild habitats above the campus.

These roofs now support a diverse mix of grassland and meadow species, including Wild Clary, Common Cudweed, Salad Burnet, Birdsfoot Trefoil, Ladies’ Bedstraw, Marjoram, and at least six species of Cranesbill.
The most unusual recent addition is Night-flowering Catchfly, a nationally declining annual “weed” now known in Oxfordshire from only a handful of sites in the north-west of the county. The plant’s sticky stems are thought to deter insects, while its flowers open at dusk to attract moth pollinators.

Spotted Orchids have also appeared on the more established roof areas, particularly between the John Henry Brookes Building and the Colonnade, further underlining the ecological richness developing in these elevated habitats.

Not all new arrivals are welcome, however. Dr Lack notes that woody seedlings such as birch, willow, sycamore, buddleia, and bramble are beginning to establish.

“Rogue tree and shrub seedlings could prove destructive for the roofs and will need to be removed,” he said.
Despite a challenging dry spring and summer, Dr Lack remains optimistic about the ecological value of the roofs and what they reveal about urban biodiversity.

“We must treasure them, whole ecosystems largely invisible above our heads but adding considerably to the biodiversity of our campus.”

To learn more about Oxford Brookes’ commitment to the environment visit the Sustainability webpage.