Synonyms: Asplenium arboreum sensu Hillebr., non Willd.; Athyrium pseudoarboreum Copel. [Hillebrand's Asplenium arboreum ß var.]

Endemic

Named for Moloka'i, the fifth largest Hawaiian island, where the type specimen was collected.

Plants medium-sized. Rhizomes short, decumbent. Fronds up to 55 cm long. Stipes thin, green or straw-colored, naked except for a few brown, lanceolate scales at bases. Blades 1-pinnate to 1-pinnate-pinnatifid, lanceolate-oblong, tips pinnatifid, chartaceous. Pinnae 7-12 pairs, long-stalked, opposite at bases, alternate distally, oblong-lanceolate to subfalcate, 5-8.2 x 1.2-2.5 cm, margins shallowly to deeply crenate, acroscopic margins notched or cut into 7-12 nearly equal, obtuse or somewhat acute lobules, occasionally deeply lobed at base, basiscopic base obliquely cut, acroscopic base truncate, parallel with rachis. Veins free, repeatedly forked. Sori on all first branches of veins, doubled at bases of pinnae, single toward pinna tips, often very long, up to 1.3 cm long, curved outward.

Historically known from mesic to wet forests, 770-1,690 m, on all major islands except Hawai'i, but now found in only a few scattered sites on East Maui (Honomanu and Polipoli).

This federally listed endangered species was said by Hillebrand to be very rare in 1888 when he first discussed it (as Asplenium arboreum).

Diplazium molokaiense, a rare, 1-pinnate fern, resembles Asplenium lobulatum in the field. It is recognized by its usually very long sori that are doubled at the bases of the pinnae, prominent veins, and usually prominent lobes at the bases of the pinnae on the distal-facing tips of the fronds. It is never proliferous.