Botanists have found a rare buttercup on Stewart Island / Rakiura, enabling them to take samples to grow in controlled conditions for the first time.

Photo: DOC / Rowan Hindmarsh-Walls

The Mount Allen buttercup was first discovered in the 1980s and spotted again by some botanists in the early 2000s.

Last month, about 50 of the plants were found by Department of Conservation botanists carrying out a survey on Mount Allen.

DOC botanist Brian Rance said they were found at six sites in the inhospitable rocky landscape.

The plant has the highest threat classification of 'nationally critical' and was on a priority list of little known species for DOC to assess its population size, threats and management needs.

Two rosettes were collected and are being grown in a climate-controlled glasshouse at Dunedin Botanic Gardens.

Photo: DOC / Rowan Hindmarsh-Walls

"Mount Allen buttercup is naturally rare because it lives in a specialised sub-alpine habitat and is one of a number of endemic plants found only on Stewart Island," said Mr Rance.

There did not appear to be any immediate threats to its survival, he said.

New Zealand has 45 named species of buttercup of which three are found only on Stewart Island / Rakiura. The most well-known is the large and showy Mount Cook buttercup.

Stewart Island / Rakiura, with its extensive intact natural areas, is an important place for plant conservation nationally.

"The Dunedin Botanic Garden is helping to conserve the Mount Allen buttercup by propagating and studying this obscure plant and hopefully being able to grow an insurance population."