lobed spleenwort

Asplenium pinnatifidum is a small fern with bright green, wrinkled, pinnatifid (lobed) fronds. These form evergreen, perennial tufts. Notable characteristics are the shiny stipe (leaf stalk), dark only at the base, and the long-tapering, variably lobed leaf blades. The fronds are monomorphic, the sterile and fertile fronds appearing the same size and shape. The roots of A. pinnatifidum are not proliferous, so it appears as clusters of leaves springing from a single rhizome. The leaves are closely spaced on the rhizome, which is frequently branched. The rhizome is about 1 millimeter (0.04 in) in diameter, covered with narrowly deltate (triangular) scales which are dark reddish-brown or blackish in color, and strongly clathrate (bearing a lattice-like pattern). The scales are 3 to 5 millimeters (0.1 to 0.2 in) long and 0.3 to 0.5 millimeters wide, with entire (untoothed) edges. The stipe is shiny and dark reddish brown at the base. This color fades to green in the upper one-third to one-half of the stipe. It is covered in scales similar to those of the rhizome at the base, which diminish into hairs in the upper part of the stipe. It may show narrow wings from the base of the leaf to near the base of the stipe. …

Native to eastern North America, A. pinnatifidum occurs in the middle and southern Appalachian Mountains, from Pennsylvania and New Jersey southwest to Alabama and the northeastern corner of Mississippi. It is also found in the Shawnee Hills and to some extent in the Ozarks, with outlying occurrences in southeastern Oklahoma and in Iowa County, Wisconsin. Early reports from New England proved to be variants of Scott's spleenwort, Asplenium × ebenoides.

A. pinnatifidum can be found on acidic rocks, often in steep habitats, from altitudes of 0 to 1,000 meters (0 to 3,281 ft). Sandstone is its usual substrate. The soil formed when these rocks weather must be subacid (pH 4.5–5.0) to mediacid (pH 3.5–4.0) to support A. pinnatifidum.

The species is considered apparently secure globally (G4), but is endangered in many parts of its range. NatureServe considers it to be extirpated in New York, where it was known from a single 1877 collection, critically imperiled (S1) in Illinois, Maryland, Mississippi, New Jersey, Oklahoma, South Carolina, and Wisconsin, imperiled (S2) in North Carolina, and vulnerable (S3) in Arkansas, Georgia, Pennsylvania, and Virginia. It is threatened by changes in land use, habitat fragmentation, and certain forest management practices.

A. pinnatifidum can be cultivated in rock gardens and terraria. It prefers medium light and will grow on a moist soil or potting mixture. Some authorities recommend adding sandstone chips to the soil.