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 235B3C43-C452-4F5E-ACD2-6D11321580F7) with original publication details: 387 1879.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:180723-1.
This name was in version 1 of The Plant List, record gcc-80184.