This name is a synonym of Apocynum × floribundum Greene.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 12902) with original publication details: Man. Fl. N. States 739 1901.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:77202-1.
This name was in version 1 of The Plant List, record kew-12902.