Mamaku
Common name: Black tree fern
Botanical name: Cyathea medullaris
The mamaku is by far the tallest of New Zealand’s native tree ferns, growing a single trunk up to 20 metres high and 30 cms across. At the top of the trunk there is a graceful crown of up to 30 curving fronds, each of which can be up to 6 metres long and 2 metres across. Very old mamaku can have the base of their trunks buttressed with a thick mat of aerial roots, increasing the diameter substantially.
It is found from sea level to 600 metres altitude throughout New Zealand, including offshore islands, and is also found across a large part of the Pacific.
A section of mamaku frond, upper surface
Close-up of under surface of leaflets
The stem at the base of the frond that grows out of the top of the trunk is called the stipe. At its base it is densely clothed in long dark brown, almost black, hair-like scales, as is the uncurling new frond. These can cause unpleasant itching if you get them inside your clothes next to your skin.
Stipes arising from the top of the trunk
The tree at GZ is relatively young, with a much older and more impressive specimen a few metres away. I was going to place the cache under that one, but in trying to get to its base I fell through the foliage and discovered that the bank was steeper than it had looked. We don’t want any injuries getting the cache, so I opted for Plan B 
.
This older specimen near GZ exhibits the distinctive hexagonal pattern of scars that are left by the falling leaves.
Close-up of scars
The cache
The cache is a red M&M container and at time of placement contained a log sheet and a flower hand stamp only. Please bring your own pen or pencil to sign the log: logs entered online that are not in the paper log in the cache will be removed. Please rehide the cache as you found it after signing the log to prevent it from being muggled: the tree is rather close to the track. Also be careful not to drop yourself down the sheer drop immediately behind the tree! Getting back to the track from there might be tricky.