Asplenium septentrionale is a small fern which grows in dense clusters superficially resembling tufts of grass.

The long, dark stems support narrow, leathery leaf blades, which may appear slightly forked at the tip.

The scales are narrowly triangular, and range in color from black to a dark reddish brown.

[2] Individual plants have an abundant number of leaves, forming dense tufts from a rhizome of about 1 millimetre in diameter, and sometimes mats on flat rocks.

[2][3] A. septentrionale is easily distinguished from other related ferns by its narrow blades, often forked at the tip.

Originally named Acrostichum septentrionale by Linnaeus in 1753, the species was placed in genus Asplenium by Georg Franz Hoffmann in 1796.

[2] A global phylogeny of Asplenium published in 2020 divided the genus into eleven clades,[6] which were given informal names pending further taxonomic study.

[7] The Schaffneria clade has a worldwide distribution, and members vary widely in form and habitat.

[8] Most members of the A. septentrionale subclade have small leaves with a long green stalk, entire or divided into two or three segments, and always grow on rocks.

[9] Other members of the subclade include the European A. seelosii and A. celtibericum and an undescribed species from Venezuela.

In 2003, Ronald Viane and Tadeus Reichstein elevated this subspecies to a species, as A. caucasicum, and described a sterile triploid formed by hybridization of the tetraploid and diploid, identifiable by its abortive spores.

[10] However, in his taxonomic revision of Indian pteridophytes, Christopher Fraser-Jenkins reduced all of these taxa to subspecific rank, with the hybrid A.

[10] It is also found in North America, principally in the Rocky Mountains of the western United States, but also in the Black Hills of South Dakota–Wyoming.

Sensitive to root disturbance, it is difficult to transplant and establish, and is rarely sold by nurseries.