Spleenwort family (Aspleniaceae)
Description: This native perennial fern produces small clumps of simple-pinnate leaves. Individual leaves are ¾1½' long and 1-2" across; the semi-evergreen fertile leaves are longer and more erect than the evergreen sterile leaves. Each compound leaf has 15-40 pairs of leaflets along its rachis (or central stalk); these leaflets are usually arranged alternately along the rachis, rather than in opposite pairs. Both the rachis and petiole of mature leaves are terete and dark purplish brown; usually they are glabrous, but sometimes sparse white hairs are present. For very young leaves emerging from the ground, the rachis and petiole can be light green. Individual petioles (about 1-4" long) are much shorter than the leaf blades. The medium to dark green leaflets are deltoid-oblong in shape, crenate or serrate along their margins, and glabrous; young leaflets often have a lustrous quality. The base of each leaflet has an ear (auricle) on the upper side that overlaps the rachis. Each leaflet has pinnate venation with a central vein and several lateral veins; the lateral veins are forked. On fertile leaves, mature leaflets develop two rows of elongated sori (spore-bearing structures) on their undersides. Attached to one side of each sorus, there is an elongated indusium (protective membrane) that eventually withers away. The spores are released to the wind during the summer or early fall. The root system consists of a short rhizome with fibrous roots; relative to ground surface, the position of this rhizome is often vertical or diagonal in its orientation.
Cultivation: This fern prefers partial sun or dappled sunlight, moist to slightly dry conditions, and soil that is loamy or rocky. Unlike many other Asplenium spp. (spleenworts), which are restricted to very rocky habitats, Ebony Spleenwort adapts to terrestrial conditions. Thus, it is more likely to thrive in gardens.
Range & Habitat: Ebony Spleenwort is occasional to locally common in the southern half of Illinois, while in the northern half of the state it is uncommon or absent (see Distribution Map). However, this fern has been spreading into new locations northward, even reaching the upper Great Lakes region. Habitats include thin upland woodlands, sandy woodlands, rocky wooded slopes, rocky cliffs and ledges (if not too sunny and dry), small meadows in upland wooded areas, rocky glades, and rocky banks along roads. In the rocky habitats, some seepage of groundwater may occur. Ebony Spleenwort is occasionally found in habitats with a history of disturbance (e.g., removal of some trees or brush in wooded areas).
Faunal Associations: Information about floral-faunal relationships is unavailable.
Photographic Location: Edge of a small meadow in an upland woodland in Vermillion County, Illinois. The use of a flash on the camera has caused the color of the leaves to wash out.
Comments: This is the largest and most adaptable spleenwort in Illinois; the attractive leaves have a delicate appearance. It superficially resembles a small-sized Polystichum acrostichoides (Christmas Fern), but the rachis and petiole of the latter fern are light-colored and very scaly. Among the various Asplenium spp. (spleenworts) in Illinois, the most similar species is Asplenium resiliens (Black Spleenwort), which has been called "Little Ebony Spleenwort." Black Spleenwort has smaller leaves (about 4-9" long & ½1" across) than Ebony Spleenwort, and the ears of its leaflets don't overlap or hide the rachis to the same extent as the eared leaflets of the latter fern. Other similar spleenworts in Illinois have leaflets that lack eared basal lobes and their leaflets are often as wide as long. Furthermore, the mature petioles and rachises of such spleenworts are light-colored (green or yellowish tan) in whole or part. Ebony Spleenwort occasionally hybridizes with other spleenworts when they occur together in the same area.