A rare wild orchid, thought to be extinct in the UK, has been found in a rooftop garden on top of Japanese investment bank Nomura in London.

The Serapias parviflora, which was first discovered in Cornwall in England in 1989, is typically found in the Mediterranian Basin and on the Atlantic coasts of France, Spain, and Portugal. The plant was considered extinct in the UK in 2009, only 20 years after its discovery, according to the BBC.

The colony found on the London rooftop is 15-plants strong. It’s an exciting addition to the 159 species of flowering plants currently living on the roof.

How the seeds arrived at the rooftop garden are unknown, but it is possible that they were carried by the winds. Another explanation is that the orchid seeds were on the plants used to create the rooftop garden over 10 years ago.

“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,” said ecologist Mark Patterson, who runs the rooftop garden.