Stems short-creeping; scales bronzy deep yellow, concolored, margins entire. Leaves arching to stiffly erect, often densely clustered, 38--75(--90) cm. Petiole 1--3 mm diam., glabrous, often glaucous. Blade fan-shaped to funnel-shaped, pseudopedate, 1-pinnate distally, 10--35 × 10--35(--45) cm, glabrous; proximal pinnae 2--7-pinnate; rachis straight, glabrous, often glaucous. Segment stalks (0.4--)0.6--1.5(--1.9) mm, dark color commonly entering into segment base. Ultimate segments long-triangular, ca. 2.5 times as long as broad; basiscopic margin oblique; acroscopic margin lobed, lobes separated by narrow (less than 1 mm) incisions; apex acute, usually entire. False indusia transversely oblong, mostly 2--5(--10) mm, glabrous. Spores mostly 45--58 µm diam. 2 n = 116.

Sporulating summer--fall. Restricted to serpentine sites where it occurs in rock clefts, on talus slopes, and in well-developed serpentine soils; 200--800 m; Vt.

Adiantum viridimontanum , an allopolyploid from a sterile hybrid between A . pedatum and A . aleuticum , is known only from north central Vermont (C. A. Paris and M. D. Windham 1988). Additional populations may eventually be located on serpentine in southern Quebec.