Botrychium pedunculosum

Stalked moonwort is a perennial with a single above ground frond up to 25 cm tall. It is divided into two segments that share a common stalk. The lower common stalk is usually reddish brown and the upper part of the plant is a dull green. The mostly sterile segment is conspicuously stalked and once to twice pinnatifid with up to five pairs of primary pinnae. The pinnae have irregular lobes and vary from pinnatifid to bifid to narrowly fan shaped and the lower ones often bear sporangia. The fertile segment is longer than the sterile segment and bears grape-like sporangia that contain thousands of spores; larger plants usually have two large ascending lateral branches.

B. pedunculosum is the only western twice-dissected moonwort in which the length of the trophophore stalk equals or exceeds the distance between the first two pinna pairs. It is also distinguished by its strongly glaucous, bluish-green color, its more or less triangular trophophore blade, and the frequent presence of two large lateral branches on the sporophore. In addition, the common stalk usually possesses a distinctive reddish- to pinkish-brown stripe leading down from the trophophore base; however, this character is also sometimes present in B. hesperium, B. michiganense, and B. matricariifolium, somewhat limiting its diagnostic value. Finally, it may be possible to distinguish B. pedunculosum by the frequent presence of sporangia on the margins of its lower pinnae. However, Farrar (2005) cautions that this attribute should be used at the population level (i.e. most of the plants in the population possess the character) rather than in identifying single individuals, as all moonwort species may exhibit this attribute occasionally, and it is really the regularity and pervasiveness of the character in B. pedunculosum (and B. ascendens) populations that is distinctive. Botrychium pedunculosum is most similar to B. pinnatum and B. hesperium, which may also have reddish common stalks and pinnatifid pinnae. It can be distinguished from both of these species by its long-stalked trophophore. It further differs from B. pinnatum in its dull gray-green (vs. bright green) color and its leathery (vs. papery) texture. It further differs from B. hesperium in its lowest pinnae pair about the same size as the the adjacent pair (vs. conspicuously larger than the adjacent pair). It may soon be necessary to distinguish this species from B. matricariifolium as well, as these species may be found to overlap in Quebec as inventory efforts proceed. B. pedunculosum can be distinguished from B. matricariifolium by the more triangular outline of its trophophore blade and pinnae that are more rhomboidal in outline (a rectangle attached at one corner) (Flora of North America 1993, Kershaw et al. 2001, Farrar 2005, Idaho Conservation Data Center 2005).

Habitats in the main part of the range include (1) mountain meadows (often moist, occasionally wet or dry) and willow thickets; (2) streamside areas, including brushy secondary-growth habitats, riparian draws with western hemlock or western redcedar, swales, and old stream channel bottoms; (3) open- to closed-canopy forests and woodlands, including western redcedar forests, coniferous forests, and brushy secondary woodlands; and (4) roadsides or other similarly open or disturbed habitats. In Alaska, the species occurs in a moist meadow under tall forbs, and in Quebec, plants are found at the base of a mountain scree slope. Common moonwort associates (at least in Montana and Washington) include B. minganense, B. lanceolatum, B. montanum, B. lunaria, and B. pinnatum. Other moonworts reported include B. paradoxum, B. ascendens, B. pallidum, B. hesperium, B. simplex, B. crenulatum and B. michiganense. 300-2000 m.