This name is a synonym of Symphyotrichum × salignum (Willd.) G.L.Nesom.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 002A8E56-714D-4CF7-8218-D83D47FBCB47) with original publication details: 56 1857.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:181598-1.
This name was in version 1 of The Plant List, record gcc-127680.