walking fern

not listed

N5 - Secure

SNR - Unranked

not listed

Walking fern is a small, attractive, easily identified fern. It occurs in North America from Quebec to Florida west to Manitoba and Arkansas. It reaches the western extent of its range in Minnesota, where it occurs in the Driftless Area in the southeast, north to the Metro Area, with scattered occurrences in Todd, Morrison, Nicollet, and Blue Earth Counties. It is also cultivated. Its unique appearance makes it one of the most easily recognized ferns in Minnesota. It is found on moss-covered cliff faces and crevices of rock outcroppings where it is protected from the wind. It grows in moist, humid conditions on thin, rocky, limey (calcareous) soil under dense or partial shade. It sometimes grows on fallen logs or on soil. It rarely grows on sandstone.

Walking fern is low growing, 1″ to 6″ in height, perennial fern that rises on a tuft of leaves from the crown of a short, slender, erect, underground stem (rhizome) and slender, fibrous roots.

The leaf stalk, variously called the stipe or the petiole, is slender, flattened, and grooved above. It is reddish-brown and sometimes shiny at the base, becoming dull and green near the top. It can vary greatly in length, from 3⁄16″ (0.5 cm) long and 0.1 times as long as the blade, to 4¾″ (12 cm) long and 1.5 times longer than the blade. There are dark brown, narrowly triangular scales at the base and minute, club-shaped hairs near the top.

The blade varies greatly in size and shape, even on the same plant. It is leathery, undivided, narrowly triangular to linear lance-shaped, ⅜″ to 11¾″ (1 to 30 cm) long, and 3⁄16″ to 2″ (0.5 to 5.0 cm) wide. The base of the blade may be heart-shaped (cordate), arrowhead-shaped with the lobes turned outward (hastate), or have ear-like lobes (auriculate). The tip may be rounded or very long and thin. When long and thin the leaf will root at the tip when it touches the ground, giving rise to a new plant. This is the feature that gives the fern its common name. The upper surface is dark green and hairless. The lower surface is pale green and hairless or sparsely hairy. The margins may be flat or slightly wavy. The lateral veins branch and rejoin before reaching the margin, forming an intertwining network with well-defined open areas near the midrib. Sterile leaves are similar in shape but smaller in size than fertile leaves.

The reproductive structures are born on the underside of the blade. There are numerous elongated clusters (sora) of spore-bearing cases (sporangia) scattered irregularly along the lateral veins on each side of the midrib. The flap of tissue covering each sorus (indusium) is inconspicuous and is attached to one side. There are 64 spores in each sporangium.

1″ to 6″

Moist. Moss covered cliff faces and rock outcroppings. Full shade. Thin, rocky, calcareous soil.

May to October

Sources

2, 3, 4, 5, 7, 24, 28, 29, 30.

Native

Somewhat rare and local

Until recently, walking fern was classified as Camptosorus rhizophyllus. It was originally described by Carl Linnaeus in 1753 as Asplenium rhizophyllum. In 1833 it was placed in a segregated genus Camptosorus due to the irregular arrangement ofr its sori. DNA studies published in 1999 and 2004 showed that the genus Camptosorus is nested within Asplenium, and the species’ original classification was restored.

Walking fern Asplenium rhizophyllum

Walking fern Asplenium rhizophyllum

looking down the hill to the frozen Mississippi River visible through the trees

taken 8 December 2015

Location: Bald Eagle Bluff SNA

Walking fern Asplenium rhizophyllum