Sadleria cyatheoides, commonly known as amaumau fern or amau, is a fern species in the family Blechnaceae, in the eupolypods II clade of the order Polypodiales, in the class Polypodiopsida. It is endemic to Hawaii and inhabits lava flows, open areas, and wet forests on all major islands up to an altitude of . Reaching a height of and a trunk diameter of , amau resembles a small tree fern. Kīlauea's Halemaʻumaʻu is named for this species. Description The young fronds are often tinged red to block harmful rays from the sun. References External links Sadleria cyatheoides. NatureServe. 2012. Blechnaceae Endemic flora of Hawaii Native ferns of Hawaii Plants described in 1824