This name is a synonym of Symphyotrichum laeve var. purpuratum (Nees) G.L.Nesom.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 98EFF2EA-EEBA-4CFC-9EB1-F4006D9A031A) with original publication details: 308 1783.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:181765-1.
This name was in version 1 of The Plant List, record gcc-140012, and has not been changed.