This name is a synonym of Penstemon alpinus f. riparius (A. Nelson) Pennell.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50079832) with original publication details: Bull. Torrey Bot. Club 25(7): 379–380 1898.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:187737-2.
This name was in version 1 of The Plant List, record tro-50079832.