The many environmental forms and juvenile stages of Botrychium simplex have resulted in the naming of numerous, mostly taxonomically worthless, infraspecific taxa. The western montane populations in the flora from Colorado to north Saskatchewan and westard are evidently distinctive, however, and may warrant subspecies or species status.

Mature, full-sized plants of these can be distinguished as follows:

Eastern Botrychium simplex : Sporophore 1--4 times length of trophophores, arising from well-developed common stalk from below middle to near top, well above leaf sheath; trophophore nonternate or if subternate, lateral pinnae smaller than central pinnae and simple to merely lobed (rarely pinnate); pinnae usually adnate to rachis, rounded and ovate to spatulate, segment sides at angles mostly less than 90°; trophophore tip undivided; texture papery to herbaceous; common in upland fields.

Western Botrychium simplex : Sporophore 3--8 times length of trophophore, mostly arising directly from top of leaf sheath, common stalk much reduced to absent; trophophore ternate with 3 equal segments (rarely nonternate, then resembling single segment of ternate blade); pinnae usually strongly contracted at base to stalked, angular to fan-shaped, segment sides at angles mostly more than 90°, like those of B . lunaria ; trophophore tip divided, usually in 3 parts including narrow central lobe; texture thin, herbaceous; habitats mainly along marshy margins and in meadows.

The eastern, typical Botrychium simplex has a common woodland and swamp shade form ( B . tenebrosum A.A. Eaton) that appears to be a persistent juvenile. It is small and extremely slender, the trophophore simple, rudimentary, and attached near the top of an exaggerated common stalk. Many intermediates between this and more typical forms exist, however, and the variation appears to be the result of different growing conditions. The persistent western juvenile counterpart differs in the generally lower attachment of the trophophore (not necessarily on the top of the sheath), greater length of the trophophore, and more herbaceous texture.