Pedatum describes the shape of a bird's foot.
Rhizome: short-creeping, scales bronzy deep yellow, concolored, margins entire.
Frond: 40 cm high by 30 cm wide, deciduous, monomorphic, blade/stipe ratio: 1:1 more or less.
Stipe: purplish-black, grooved above, to 2 mm diameter, glabrous, occasionally glaucous or a few scales at the base, vascular bundles: one v-shaped bundle.
Blade: pedate, the primary divisions then pinnately divided, fan-shaped or almost circular, membranaceous to papery, glabrous.
Pinnae: 6 to 10 pair, oblong, those closest to the stipe longer, diminishing steadily outwards, slightly tapering to the base, abruptly tapering to the apex; strictly speaking, not really paired; pinnules alternate, oblong, incised on the upper margin; margins crenate; veins free, forking from the main vein along the lower margin.
Sori: oblong, submarginal on the upper margin of the pinnule, indusium: false, inrolled margins, sporangia: yellow or yellowish brown, maturity: summer to fall.
Dimensionality: The blade is held horizontally, at 90° to the stipe; the FNA gives the height as 75 cm, what it is on the herbarium sheet, not what it is in the real world..
Habitat: rich, deciduous woodlands.
Distribution: eastern North America.
Hardy to -35°C, USDA Zone 3.
and Adiantum aleuticum
are very, very similar, the nomenclatural history for the latter providing testimony. The division into two specific taxa is recent, the keys in the Flora of North America
often enough leading to unexpected results. One difference, not in the key, stands out: A. aleuticum
sometimes has ascending or vertical pinnae, A. pedatum
always has horizontal. This is, of course, unsatisfactory.