Asplenium petersenii Kunze; A. japonicum Thunb.; Athyriopsis petersenii (Kunze) Ching; Athyriumjaponicum (Thunb.) Copel.; Diplazium petersenii (Kunze) Christ; Lunathyriumjaponicum (Thunb.) Sa. Kurata; L. petersenii (Kunze) H. Ohba

Naturalized

Origin of name petersenii is unknown.

Plants medium-sized, terrestrial. Rhizomes slender, medium-creeping to decumbent, 3-4 mm diam. Fronds never proliferous, 30-60 cm long. Stipes well clothed with multi-cellular septate hairs, hairlike scales, and scales. Blades ovate-lanceolate to deltate, 1-pinnate-pinnatifid to 1-pinnate-pinnatisect, tapering abruptly to pinnatifid acuminate tips, hairy with multicellular septate hairs, and hairlike scales. Pinnae 8-12 pairs. Ultimate segments obtuse, margins serrate. Sori medial, linear. Indusia thin.

Native to tropical and subtropical regions of eastern Asia. It is also naturalized in scattered areas of the southern United States, New Zealand, Australia, and South America. This aggressive weed was first collected in Hawai'i in 1938 and was reported to be spreading in the Kohala Mountains on Hawai'i in 1950. It has since spread rapidly and is now common and widely distributed along trails, stream-sides, and disturbed forest floors as well as in intact native forests, 170-1,325 m, all major islands.

Deparia petersenii may be distinguished from other Hawaiian Deparia by its stipes, rachises, midribs, and blades heavily clothed with multicellular hairs, hairlike scales, and scales. It has slender rhizomes, shorter triangular blades, and lacks pro-liferations at the frond tips.