Diplazium pycnocarpon (narrow-leaved glade fern, narrow-leaved-spleenwort, glade fern) is a tall slender-leaved fern growing as individuals with 5 to 6 leaves. The plant spreads by creeping underground stems allowing a small colony to develop over time. The leaf blade is oblong-lanceolate and once-pinnate, unlike the closely related Athyrium. Leaves grow to about 90 cm (36 in) long and 15 cm (6 in) wide. The pinnae are linear and entire. Fertile leaves are similar but erect, narrower than sterile leaves and with longer stipes. The sori are long and narrow in two lines along the underside of a leaf pinna, giving rise to its specific epithet pycnocarpon ('crowded fruits').
Its common name description "narrow-leaved" is reflected in its original specific epithet by André Michaux in 1803: angustifolium (angustus 'narrow' + folium 'leaf'). Michaux classified it in the genus Asplenium.
Endemic to eastern North America. Widespread from southern Ontario to the Gulf of Mexico and west to Minnesota and Arkansas. Usually found as isolated plants or colonies. See Flora of North America for distribution map.
Grows in lighter parts of mesophytic forests and in ravines in moist but well-drained, neutral to basic soils.