All through the kānuka/mānuka badlands and especially down the slope around the wetlands there are large grassy masses of sharp-edged sedges called gahnia. The Māori name is tākahikahi, which refers to the sharp edge of the leaf.
When growing densely they are very difficult to walk through, and best admired from a distance. They produce tall plumes of grassy flowers and masses of black or orange nuts; at one time probably an important food for birds. Gahnia sedges are characteristic of Australasia, but also extend through the Pacific and South East Asia. Three species are present in the park. They produce enriched soil that attracts the attention of wild pigs which damages the tussocks but also buries the seed.