Trophophores converted entirely to second fertile segment, stalk 1/2 length of fertile segment. Sporophores double, 2 per leaf, 1-pinnate, 0.5–4 cm. 2n =180.
Habitat: Sporophores in June to August. Difficult to detect, plants usually hidden under other vegetation, in snowfields, secondary growth pastures
Elevation: 1500–3000 m
Alta., B.C., Sask., Mont., Utah.
The leaf structure of Botrychium paradoxum is uniform and unique. Very rare teratological individuals of other moonwort species may have trophophores partially or wholly transformed into sporophores.
Botrychium × watertonense W.H. Wagner, known only from one locality in western Alberta, is the sterile hybrid of B. hesperium and B. paradoxum. It can be identified by its trophophore pinnae; all are bordered with sporangia. It may reproduce by some unknown mechanism, such as unreduced spores (W.H. Wagner Jr., F. S. Wagner, et al. 1984).
Of conservation concern.