A perennial fern growing as a cluster of leaves from a rhizome, purple cliff brake is usually found growing from crevices in limestone or dolomite rocks or in rocky soils near them. The stiff, wiry stems are dark reddish brown to black, with dense, short, curly hairs on the upper surface. In general outline, the entire leaf is triangular and is 1–3 times compound. Leaflets are leathery and sometimes have 1 or 2 lobes at the base, sometimes with a few, jointed hairs along the undersurface midvein. Sterile leaflets are lanceolate to ovate or oblong. Fertile (spore-bearing) leaflets are longer and thinner than the sterile ones, and spores are borne in a continuous band along the outer margin, protected by the recurved edge of the leaflet. Spores are produced June–September.
Similar species: Smooth cliff brake (P. glabella) has leaflets that are all about the same shape, and the leaf stalks and midveins are hairless or have only a few scattered hairs. It is also a smaller plant, with leaves only reaching about 9 inches long, and leaflets only reaching about 1 inch in length.
Habitat and Conservation
Ferns have a two-part life cycle. The plants we usually see are called sporophytes, because they produce spores that germinate and become the other part of the life cycle, the gametophytes. Gametophytes in this family of ferns are small, green, flat, kidney- or heart-shaped plants that few people notice. The gametophytes produce eggs and sperm, which unite to become a new sporophyte plant.
Cliff brakes, however, are famous for hybridizing with each other, and for creating offspring that are polyploid (possess more than two copies of genetic information in each cell), and for reproducing via apogamy. Apogamy is when a new sporophyte plant forms without fertilization — so it has the same number of genetic copies as the gametophyte. Purple cliff brake is an apogamous species — that means it essentially bypasses the sexual reproduction part of the typical fern life cycle.
Why is it “brake” and not “break”? It is logical to think of these cliff-loving ferns as plants that ultimately help “break apart” the rock surfaces of bluffs, but the word brake, with Middle English and Scandinavian roots, actually means “fern.” This is why we don’t call these plants “cliff brake ferns.” For the same reason, there is a fern called “bracken” and not “bracken fern.”
Purple cliff brake and its relatives were used historically by Native Americans to treat a variety of ailments.