Equisetum hyemale var. robustum (A. Braun) A.A. Eaton
Equisetum hyemale var. robustum (A. Braun) A.A. Eaton is a synonym sensu Christenhusz et al., 2019 of:
Equisetum hyemale subsp. affine (Engelmann) Calder & Roy L. Taylor, an accepted subspecies name sensu FNA Ed. Comm., 1993.