This name is a synonym of Penstemon rattanii subsp. kleei (Greene) D.D. Keck.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50119033) with original publication details: Bull. Torrey Bot. Club 10(12): 127 1883.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:808154-1.
This name was in version 1 of The Plant List, record tro-50119033.