'''Ama'u''' is a species of [[fern]] in the family [[Blechnaceae]] that is [[Endemism|endemic]] to Hawaii. It inhabits [[lava]] flows, open areas, and [[Hawaiian tropical rainforests#Wet forests|wet forests]] on all major [[Hawaiian islands|islands]] up to an altitude of {{convert|1676|m|ft}}. Reaching a height of {{convert|0.9|-|1.5|m|ft}} and a trunk diameter of {{convert|7.5|-|10|cm|in}}, 'ama'u resembles a small [[Cyatheales|tree fern]].<ref name="CFTH">{{cite paper |url=http://www.ctahr.hawaii.edu/forestry/data/CommonTreesHI/CFT_Sadleria_cyatheoides.pdf |format=[[PDF]] |title={{okina}}Ama{{okina}}u, sadleria |first=Elbert L. |last=Little Jr. |coauthors=Roger G. Skolmen |publisher=[[United States Forest Service]] |year=1989}}</ref>