An exotic plant species previously unknown to science has been discovered growing in a hothouse in London’s famous Kew Gardens.

Botanists discovered the carnivorous pitcher plant – now named Nepenthes zygon – had been growing at Kew for almost a decade and helping to keep down cockroaches, before anyone realised it didn’t match any species on record.

It originated from the Philippines where it was collected as a seed by a plant hunter in 1997 and donated to Kew in 2004 as a seedling to be placed in a tropical glasshouse.

It had been labelled as the pitcher plant Nepenthes copelandii but investigations by Martin Cheek, of Kew, and Matthew Jebb, of the National Botanic Garden of Ireland, have now shown it to be a previously unknown species.

When Dr Cheek became suspicious about the plant’s labelling he struggled to say exactly what it was but had no idea it was new to science.

He waited for it to produce flowers, which are important for the correct identification of pitcher plants, before he was able to establish that the specimen was from a completely unrecorded species.

His research established that another specimen was collected more than a century ago by an American plant hunter but it was stored in herbaria in Leiden and Edinburgh without anyone being able to classify or name it.

“It’s very unusual to find a new species in this way,” he said. “People will travel thousands of miles to discover new plants but here was one right under our noses.”

Kew holds more than 50 types of pitcher plant and most of them are kept in the tropical nursery for researchers to study but Dr Cheek hopes N. zygon will soon be placed on public view in the Princess of Wales glasshouse along with N. robcantleyi, a huge species of pitcher plant he helped discover in 2011.

Pitchers and the other carnivorous plants at Kew help keep pests under control – some are even big enough to consume mice and rats – and Dr Cheek said they are particularly useful at reducing the number of cockroaches in the glasshouses.

“Cockroaches, gruesome things, are certainly trapped by Nepenthes plants,” he said. “It’s quite satisfying sometimes seeing them squirming at the bottom of a pitcher.”

More than 100 species of plants, more than a dozen of them carnivorous pitcher plants, have been co-discovered by Dr Cheek but as a botanist it is difficult to win funding for projects because, he said, plants rarely capture the public imagination.

“The priority for mankind should be to go out and find out what these plants are and evaluate their uses for mankind. Many medicines derive from plants but most of the world’s plant species haven’t been fully identified for their uses,” added Dr Cheek.

The plant was described along with two others in a paper in the journal Blumea. It has been classified as critically endangered.