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 329914) with original publication details: Ann. Missouri Bot. Gard. 17: 112 1930.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:16613-2.
This name was in version 1 of The Plant List, record kew-329914.