The 15-strong army of small flowered tongue orchid ‘Serapis parviflora’ were discovered on June 4 on Nomura International’s 11th-floor garden.
It is the first time the Serapis parvifloras have been seen in the country since arriving in Cornwall in 1989 and they represent the entire known wild UK colony of the species.
Mark Patterson, Nomura’s Ecologist, who spotted the plants, said he did not know how the orchids got there but described it as “plausible” that they have “spontaneously colonised naturally without assistance.”
“Orchid seeds are incredibly small and can travel great distances by wind.
“The plants could have originated on the Continent and been brought over the Channel on southerly winds which frequently bring Saharan dust deposits to the capital.”
Mr Patterson, who manages the roof and discovered the plants during a monthly plant survey, added: “Once settled on the Nomura roof the seeds would have formed a symbiosis with a mycorrhizal fungus enabling them to germinate and grow – while possible, the odds are astronomical.”
Although he said another explanation could be that they were planted decades ago and took time to mature.
Orchid expert and author Mike Waller, said: “To find Britain’s second colony of Small-flowered Tongue Orchids is exciting in itself but to find them on a green roof in the City of London is extraordinary – on another level, if you’ll excuse the pun. This is clear evidence that with patience and dedication, even the most unlikely places can become havens for some our rarest wildlife.”
But this is not the first time rare orchids have been found on the bank’s rooftop. Back in 2018 Mr Patterson also discovered London’s largest colony of Green Winged Orchids growing on the Nomura roof, which had increased to 10 plants in 2021.
