Although closely resembling the native sword fern, N. exaltata hawaiiensis, the non-native fern growing here, N. brownii (syn. N. multiflora), is the dominant sword fern found across the lowlands of O‘ahu. At Nā Pōhaku o Hauwahine, the smaller native fern—kupukupu or Nephrolepis cordifolia—is common (look for it on the right of the trail to the east).

Closely resembling the sword fern here—native N. exaltata hawaiiensis or ni‘ani‘au—is found in wetter areas at higher elevations. The non-native can be distinguished from native ni‘ani‘au by the former having a row of tiny dense hairs along the upper surface of the midrib of each pinna (leaf segment).

The ferns growing here arrived naturally at the park and are being retained because of their resemblance to ni‘ani‘au (we call this an educational exemption). But this particular fern is not native.