Etymology Retroso = backward or downward pointing; palea = scale, referring to the orientation of the stipe scales.

Description Rhizome: erect, stout, short.
Frond: 120 cm high by 30 cm wide, deciduous, monomorphic, blade/stipe ratio: 3:1.
Stipe: grooved, scales dense, membranous, pale brown, lustrous, ovate, to 2 cm at the base, shorter upwards, accompanied by narrow, linear, downward-pointing scales, vascular bundles: 5, in an arc.
Blade: 2-pinnate, lanceolate, slightly narrowed at the base, glossy, thick, scales on lower surface of rachis broadly ovate, pale brown, membranous, to 6 mm long, adpressed downwardly.
Pinnae: 20 to 25 pair, composed of 15-20 pinnules; pinnules the upward pointing pinnules closest to the rachis distinctly larger, pinnules ending in a sharp point; margins dentate; veins free, forked.
Sori: round, medial, indusium: peltate, sporangia: yellow or brownish to black.
Dimensionality: the lowest pinnae bending above the blade plane and towards the base.

Culture Habitat: forest floor. Distribution: Japan. Hardy to -25°C, USDA Zone 5.

Synonyms
Polystichum aculeatum var. retroso-paleaceum Kodama