Sadleria pallida

Fern Spotlight: ʻAmaʻu

By Clyde Imada, Research Specialist in Botany, Natural Sciences

Often iconically featured in articles on Hawaiian natural history because of its large, eye-catching, reddish-hued young fronds, the ‘ama‘u is indeed a special Hawaiian fern. It belongs to the genus Sadleria, which was named for Joseph Sadler (1791–1849), a botanist who studied the ferns of his native Hungary. Sadleria has the distinction of being one of only two fern genera restricted (endemic) to Hawai‘i. Its six species range from tree ferns with trunks up to ten feet tall in dense wet forest; to delicate, pendant ferns clinging to dripping, mossy cliffs; to pioneer species on hot, exposed, recent lava flows. Hawaiian names applied to the larger species include ‘ama‘u, ma‘uma‘u, and the plural ‘ama‘uma‘u.

Sadleria cyatheoides

Sadleria is famously associated with the often fiery Halema‘uma‘u lava pit in Kīlauea, popularly translated as “Maʻumaʻu Fern House” for the abundance of ‘ama‘u growing in the vicinity of the crater. However, a sampling of other published sources provide alternate interpretations. Otto Degener in 1973 related that the ancient name of the fire pit was Lua Pele (Pit of Pele) in honor of the goddess of volcanoes, and that Halema‘uma‘u was a later name bestowed either in recognition of a lava cone, now long gone, that resembled temporary shelters built of ‘ama‘uma‘u by Hawaiians on their visit to the region, or, less likely, because of the former abundance of this fern on the crater floor. E. S. Craighill and E. G. Handy in 1972 interpreted its meaning as “House of Ferns” in reference to the lava there cooling in fanciful fern-like forms. A National Park trail guide notes that the name Halema‘uma‘u is taken from a legendary event in which the pig demigod Kamapua‘a took on the body form of the ‘ama‘u fern to protect himself from the fires of Pele. The Hawaiian poetic name for the fern, pua‘a ‘ehu‘ehu (red pig) fits well with this tale.

‘Ama‘u was exploited (along with hāpu‘u) in a commercial enterprise between 1850 and 1885 in the lush tree fern forests of what is now Hawai‘i Volcanoes National Park. The plentiful brown, wool-like scales (called pulu) covering the growing tip and frond stalks were harvested as stuffing for mattresses, pillows, and upholstery, shipped mainly to the West Coast. At its peak, over 300 tons of pulu was harvested annually, and the forests were being depleted because the larger trunks were being cut down for easier harvesting. The industry came to a halt when it became clear that the pulu fibers were too brittle and wadded up over time, and more suitable stuffing materials were eventually substituted. In ancient times pulu had been used by Hawaiians for dressing wounds and embalming the dead.

Sadleria squarrosa

With support from Hawaiʻi Tourism’s Aloha ʻĀina Program, Bishop Museum is updating their databases of ferns and flies as part of the project “Protecting Hawaiʻi’s Resources: The Story Our Data Can Tell.”

Image 1: Sadleria pallida is often found in the wet, windswept summit zone.

Image 2: Sadleria cyatheoides is one of the first plants to colonize new lava flows.

Image 3: Sadleria squarrosa (‘apu‘u) is a pendent (hanging down or overhanging) species growing on wet mossy rock faces.

Photos by Clyde Imada