Trophophore stalk 0--1 mm; blade dark green, oblong, 1-pinnate, to 10 × 4 cm, thick, fleshy. Pinnae to 9 pairs, spreading, mostly overlapping except in shaded forest forms, distance between 1st and 2d pinnae not or slightly more than between 2d and 3d pairs, basal pinna pair approximately equal in size and cutting to adjacent pair, broadly fan-shaped, undivided to tip, margins mainly entire or undulate, rarely dentate, apical lobe usually cuneate to spatulate, notched, approximate to adjacent lobes, apex rounded, venation like ribs of fan, midribs absent. Sporophores 1--2-pinnate, 0.8--2 times length of trophophore. 2 n =90. Leaves appearing in spring, dying in latter half of summer. Open fields, occasionally forests in southern occurrences; 0--3700 m; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Maine, Mass., Mich., Minn., Mont., Nev., N.H., N.Mex., N.Y., Oreg., Pa., S.Dak., Utah, Vt., Wash., Wis., Wyo.; s South America; Eurasia; Pacific Islands in New Zealand; Australia. Botrychium lunaria grows with many other species of Botrychium , occasionally hybridizing with them. This species, geographically the most widespread of the moonworts, has notably uniform morphology.
Plants 3-18+ cm, wholly glabrous; blade and sporophore ±erect in bud; blade bright green in life, sessile or on a short stalk to 5 mm, borne near the middle of the apparent stem and seldom surpassed by it, 1.5-7 נ0.7-3(-3.5) cm, distinctly pinnate, with (1)3-6(7) pairs of similar pinnae, these sessile, crowded and often overlapping, dichotomously veined, without a midrib, flat, broadly flabellate, broader than long, the proximal margin forming an obviously retrorse angle with the rachis, the lowest pair of pinnae not evidently different from the next pair; sporophore and its stalk each 0.5-7 cm, subequal or either one the longer. Open fields and meadows, or sandy or gravelly streambanks; circumboreal and also scattered in the S. Hemisphere, in our range s. to N.Y., Mich., and Minn. June-Aug.
The foregoing description applies to the widespread, nomenclaturally typical, diploid (2n=90) phase of the species. It passes freely into a diploid shade form, often called var. onondagense (Underw.) House, with the blade on an evident stalk generally over 5 mm, the pinnae more remote, often somewhat spoon-shaped rather than flat, and not notably wider than long, the proximal margin diverging widely from the axis. A distinctive dwarf diploid ally of var. onondagense, often with persistent gametophytes, occurs in mature deciduous forests in Mich., Wis., and Minn., and has been called B. mormo W. H. Wagner. A more yellow- green tetraploid (2n=180), morphologically scarcely separable from diploid var. onondagense, is also wide- spread in the N. Amer. portion of the range of B. lunaria, and has been distinguished as B. minganense Vict. A hexaploid much like the minganense phase has been described as B. campestre W. H. Wagner.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.