This name is a synonym of Penstemon speciosus subsp. kennedyi (A. Nelson) D.D. Keck.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50110669) with original publication details: Proc. Biol. Soc. Wash. 17(11): 97 1904.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:187569-2.
This name was in version 1 of The Plant List, record tro-50110669.