Purple Cliff Brake

Pellaea atropurpurea

Purple_Cliff_Brake_Clifty_Creek_10-23-14.jpg

Photo of purple cliff brake growing from a rock crevice, with a hand propping up one of the fronds
Purple cliff brake grows from crevices in limestone and dolomite rocks, or in rocky soils near them. Its leathery, blue-gray, narrowly oval or triangular leaves are not very fernlike.
Other Common Name
Purple-Stem Cliffbrake
Family

Pteridaceae (maidenhair ferns)

Description

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.

Size

Leaf length: 2 to 20 inches; leaflet length: ¼ to 1½ inches.

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Photo of purple cliff break leaflets and leaf stem
Purple Cliff Brake Leaflets
The stiff, wiry stems of purple cliff break are dark reddish brown to black, with dense, short, curly hairs on the upper surface.

Purple_Cliff_Brake_Painted_Rock_CA_12-20-18.jpg

Photo of purple cliff brake growing on the top of a bluff
Purple Cliff Brake at Painted Rock CA
Purple cliff brake has two different kinds of leaves. Sterile leaves (at left) have rounded, wider leaflets. Spore-bearing leaves (at right) have leaflets that are longer and thinner than the sterile ones.

Purple_Cliff_Brake_fertile_leaflets_Clifty_Creek_10-23-14.jpg

Photo of purple cliff brake fertile leaflets, underside showing false indusia
Purple Cliff Brake Fertile Leaflets
The spore-bearing leaflets of purple cliff brake are longer and thinner than the sterile ones. The spores are borne in a continuous band along the outer margin, protected by the recurved edge of the leaflet.

Purple_Cliff_Brake_habitat_Clifty_Creek_10-23-14.jpg

Photo of purple cliff brake growing from crevice between rocks on a wooded slope
Purple Cliff Brake
Purple cliff brake may be found growing among rocks in soil, as well as in crevices and on ledges of limestone and dolomite bluffs and boulders.

Purple_Cliff_Brake_sterile_leaves_Clifty_Creek_10-23-14.jpg

Photo of purple cliff brake, showing 3 sterile leaves
Purple Cliff Brake Sterile Leaves
The sterile leaves (fronds) of purple cliff brake are shorter, with more rounded leaflets, than the fertile leaves.

Purple_Cliff_Brake_rock_face_Clifty_Creek_10-23-14.jpg

Photo of a purple cliff brake growing from a rock face
Purple Cliff Brake Growing From Rock Face
Key identification features for purple cliff brake include the dense, curved hairs on the upper side of the wiry, purplish, shining leaf stems, and the leathery, untoothed leaflets.
Habitat and conservation

Occurs on crevices and ledges of limestone and dolomite bluffs, boulders, rock outcrops, and sinkholes, sometimes in soil of dry, rocky forests adjacent to dolomite glades. Compared to the similar smooth cliff brake, which is pretty limited to exposed cliff faces and similar habitats, purple cliff brake is more likely to be found in soils and has a wider statewide distribution.

Distribution in Missouri

Scattered nearly statewide, but most common in the Ozarks.

Life cycle

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.

Human connections

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.

Ecosystem connections

Little information is available about the connections between purple cliff brake and insects and other animals. As enduring plants of cliff, bluff, and other dry, rocky habitats, cliff brake surely provides cover for insects and spiders that live in those natural communities. And small birds can perch on these ferns to forage for the insects and spiders! Also, like other vegetation that grows in rock crevices, these ferns contribute to the weathering of rock faces.