This has been considered a hybrid of laxiculmis and digitalis (F), but such origin is not supported by recent evidence (A. Reznicek et al. in FNA 23). Ranges and habitats of copulata do not appear to differ much from typical laxiculmus, but it is concentrated in the mid-west and may be typical of damper richer soils. It has been generally treated as a variety of laxiculmis, but evidence for species status is persuasive (W; R. Naczi, pers. comm.). Leaves of copulata are usually bright green (versus glaucous) and narrower (the widest 5.3-8.3 mm versus 6.4-11.8 mm). Its staminate spikes tend to be shorter: the longest per plant usually 6-20 mm versus 12-25 mm.