Conservation Department staff and volunteers spent hours this week sloshing through a swamp and counting tiny orchids.
It's been an annual early summer task for at least the last five years, biodiversity ranger Sara Treadgold said.
The aim is to find out whether a critically endangered native New Zealand swamp orchid thrives better when tall vegetation around it is limited.
To answer that question, the department has marked out six large squares on conservation land within Ihupuku Swamp, near Waverley. It's one of only a few places where the orchid is known to survive.
Each year three of the squares have their tall vegetation cut down with a brushcutter. The other squares are left to grow naturally.
Then, in early summer when the orchids are emerging and flowering, staff and volunteers painstakingly count the number of orchid plants in each square.
On Wednesday and Thursday this week about six people were on hands and knees, pushing aside rushes and raupo to look for the tiny plants.
This year's count may provide enough information to answer the question. If not the squares will be cut and the orchids counted again next year, Ms Treadgold said.