This name is a synonym of Apocynum androsaemifolium subsp. pumilum (A.Gray) B.Boivin.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 12821) with original publication details: Bull. Torrey Bot. Club 37: 261 1910.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:77122-1.
This name was in version 1 of The Plant List, record kew-12821, and has not been changed.