northern lady fern

Like other species in the genus Athyrium, A. angustum features light green fronds which grow in clumps typically 2-3 feet tall. One frond may have 20-30 pairs of non-opposite pinna. A. angustum is difficult to distinguish from its close relatives, but is proposed to be identifiable by having stipes with lengths 1-1.5x the frond length (as opposed to the relatively longer stipes of A. asplenioides) and narrower fronds. The rootstock is considered slow-growing compared to A. asplenoides, leading to more distinctive clustering of the fronds, but less clustering than in A. filix-femina. The scales grow up to 1 cm long and 1.5 mm wide, and are linear-lanceolate with a wide base.

A. angustum is distributed broadly across the northeast of North America, ranging from Labrador to Manitoba in the north and south potentially as far as Tennessee and North Carolina, although older authors limited the southern border of its range to Pennsylvania and northern Missouri.

Athyrium angustum has been described as "small but easy-to-grow" for shady landscaped areas, including near streams or ponds.