Plants medium-sized, terrestrial. Rhizomes short-creeping. Fronds arching to pendent, 25-60 ( -100) x 20-60 cm. Stipes dark brown to black, glabrous, shiny. Blades 2-to 3-pinnate, ovate-lanceolate to deltate-ovate, tips long-attenuate. Pinnae 8-14 pairs, in large fronds several basal pinnules of lower pinnae becoming again pinnate. Acroscopic basal pinnules overlapping the rachises. Ultimate segments obovate to rhomboid or fan-shaped, 1-2(-3) cm on a side, stalks around 2 mm long, mostly attached centrally at base. Veins ending in small marginal sinuses (except for those ending at sori). Sori 4-10 per segment, U-shaped at bases of small sinuses. Indusial flap reniform.

Adiantum 'Edwinii' was first collected above Waikapu on Maui in 1981 and is now known at elevations up to 500 m from a cliff along 'lao Valley Road, Olowalu area on Maui, and on Lana 'i. Its current habitat appears to be on rather dry, steep rock walls, and talus slopes, but its range apparently is expanding. Better recognition and more collections will clarify its distribution, habitat, and population size.

Adiantum 'Edwinii' is probably a cultivar of A. raddianum, a native of the American Tropics, but it is also possibly a hybrid or a cultivar of A. concinnum, a native of southern Mexico to northern South America.

Adiantum 'Edwinii' may be recognized by its U-shaped sori, fronds up to 100 cm long and 60 cm wide, and the pinnules closest to the rachis overlapping the rachis on the side toward the frond tip.