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.