Department of Conservation staff planted the rare pygmy button daisy above Paratu Cave in Barnett Park.
They hope the location has the damp and isolated conditions needed for it to flourish.
The small, branching daisy only grows in two other South Island locations – Mt Pleasant and the Rai Valley in Marlborough.
DOC workers also plan to study the plant's impact on the valley's ecosystem.
Known as Leptinella nana, the small herb is part of the daisy family, Asteraceae.
While it is rare to find the daisy in the wild, it has previously been known to grow in north-eastern areas of the South Island in forest to coastal areas where there is shelter and a supply of moisture.
But it is now one of New Zealand’s most threatened plant species, and is classed as nationally critical. In the North Island, it is only known to grow at one site near Titahi Bay.
The daisy has struggled to overcome competition from other plants and weeds, increased erosion, excessive trampling by people and animals, loss of seed dispersal from birds and other animals, and indiscriminate herbicide use. Slugs are also a threat for the pygmy button daisy.
