Photo © Val Goodnow CLICK PHOTO FOR A LARGER IMAGE

Asplenium trichomanes L.

Maidenhair Spleenwort

Aspleniaceae (Spleenwort family)

Taxonomy: Two subspecies are recognized in Flora of North America - ssp. trichomanes and ssp. quadrivalens. The disposition of Idaho material needs to be determined.

General Description: A small fern with glabrous, evergreen fronds clustered from the base of the plant. The spreading fronds are 7-35 cm long, and pinnately divided into numerous pairs of oblong to oval pinnae that are reduced in size toward the tip. The pinnae are about 5 mm wide and entire-margined below, but shallowly lobed toward the tip. The rachis is shiny, reddish-brown and tends to persist after the pinnae have fallen. Spores are borne in 1-4 clusters arranged along the veins on the underside of the pinnae, and are partially covered by the flap-like indusium.

Illustration.

Field Identification Tips: The glossy, reddish-brown stems tend to persist for several years after the pinnae have been shed, and in aggregate may even be more numerous than the living fronds.

Phenology: Fronds mature in June-July.

Similar species: A. trichomanes-ramosum (A. viride) can be differentiated by its weakly evergreen green color, a dark brown rachis, and naked sori in radial rows near the pinnae margins.

Photo © Charmaine Refsdal-Delmatier CLICK PHOTO FOR A LARGER IMAGE

Habitat: Moist cliff crevices and talus slopes in the montane zone.

Global Distribution: Interruptedly circumboreal, extending southward in North America to the Southeastern states, and to Oregon, Washington, northwestern Montana, and Idaho.

Idaho Distribution: Known from the lower Boundary Creek area less than one mile south of the Canadian border. There is also a collection from a small tributary of the North Fork Clearwater River that has never been relocated.

References:

Flora North America Editorial Committee. 1993. Flora of North America, Vol. 2. Pteridophytes and Gymnosperms. Oxford University Press, Inc., New York. 475 pp.

Lellinger, D. B. 1985. A field manual of the ferns and fern allies of the United States and Canada. Smithsonian Institution Press, Washington D.C., 389 pp.

Lorain, C. C. 1989. Field investigations of three Region 1 sensitive species on the Clearwater National Forest: Asplenium trichomanes Maidenhair spleenwort), Thelypteris nevadensis (Sierra woodfern), and Dodecatheon hendersonii (Henderson's shooting star); plus new locations for additional sensitive species. Report prepared for the Clearwater National Forest by the Idaho Department of Fish and Game, Conservation Data Center, Boise. 19 pp. plus appendices.

Montana Natural Heritage Program. Montana rare plant field guide. Available at: http://nhp.nris.state.mt.us.

Moran, R. C. 1982. The Asplenium trichomanes complex in the United States and adjacent Canada. American Fern Journal 72(1): 5-11.