Athyrium thelypterioides is a fern from a short, creeping rhizome.
Leaves 35-110 cm; blade longer than stalk, 13-22 cm wide, once pinnate and pinnately lobed, tip sharply long-pointed, pinnately divided, basal leaflets reduced and pointing downward, midrib (rachis) hairy, slightly scaly, hairy, leaflets 15-20 per side, stalkless, tips long-pointed, deeply, regularly lobed, lobes to 1.3 cm long, 0.6 cm wide, oblong, round-tipped with margins entire to barely toothed.
Spore cases elongate, to 0.2 cm, 3-7 pairs per side, along pinnate veins of leaflet lobes, silvery with yellowish hairs, becoming pale brown (Cobb 1963).
Wetland status: FAC.
Frequency in NYC: Very infrequent.
Origin: Native to NYC.
Habitat: Moist woods in rich soil pH 4.5-7, tolerant of shade, intolerant of fire, salt, anaerobic soil, drought (USDA, NRCS 2006).