This name is a synonym of Penstemon cyananthus var. subglaber (A. Gray) N.H. Holmgren.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 29204326) with original publication details: Syn. Fl. N. Amer. 2(1): 262 1878.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:290697-2.
This name was in version 1 of The Plant List, record tro-29204326.