THIS rare orchid has been found flourishing in the unlikely setting of a Dorset sewage works.

The protected plant, an early spider orchid, was discovered growing on a grass roof at Swanage sewage treatment site.

Ecologists at Wessex Water were tipped off to the possibility after members of the public told them another rare orchid was spotted on the roof last summer.

Ellen McDouall, senior conservation ecologist at Wessex Water, said: “The roof has only existed for 10 years and the orchids take that long to flower. We don’t know how they got on the roof – whether seed was in the soil or blown in from nearby.

“Thankfully the roof of the sewage treatment works is under no particular operational pressure, so we are hopeful we will be able to actively manage the land for the benefit of the plant.”

The UK’s early spider orchid populations are restricted to parts of southern England, and the plant is regarded as rare. Although, where they do grow, they can so in significant numbers.

Purbeck’s limestone cliffs are one of three UK strongholds for the species, the others being Kent and Suffolk.

Anyone uprooting, cutting, selling or destroying the early spider orchid could face arrest, as it is protected under Schedule 8 of the Wildlife and Countryside Act.

Ellen said: “It is very important that we constantly assess the potential impact of our operations upon wildlife and this is a key component of our ongoing biodiversity action plan.”

The early spider orchid is also used as part of the Dorset Wildlife Trust’s (DWT) logo.

A DWT spokesman said: “This is a lovely find as the early spider orchid is nationally scarce, with around 75per cent of the population being found in Purbeck, and the rest along the south coast to Kent and Suffolk.”