Trophophore stalk 2--15 cm, 1.5--2.5 times length of blade rachis; blade dull bluish green, ± plane, 2--3-pinnate, to 15 × 20 cm, ± leathery. Pinnae to 5 pairs, usually remote, horizontal to ascending, distance between 1st and 2d pinnae not or slightly more than between 2d and 3d pairs, undivided except in proximal 2/3--3/4. Pinnules obliquely ovate, margins finely crenulate to denticulate, apex rounded to acute, venation pinnate. Sporophores 2--3-pinnate, 1.5--2.5 times length of trophophore. 2 n =90. Leaves green over winter, sporophores seasonal, new leaves appearing in spring. In moist, shady, acidic woods and swamps; 0--1200 m; N.B., Ont., Que.; Conn., Del., D.C., Ind., Ky., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., Vt., Va., W.Va., Wis. Botrychium oneidense commonly occurs with B . dissectum and B . multifidum . Young individuals of both may resemble B . oneidense (W.H. Wagner Jr. 1961b).
Much like the less-dissected phase of no. 8 [Botrychium dissectum Spreng.], but the persistently green, 2-3 times pinnate blade with mostly obtuse or rounded ultimate segments, the major segments tending to be ovate; 2n=90. Rich, moist woods and swamps; N.B. to Ont. and Minn., s. to N.C. and Ind. Aug.-Nov.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.