This name is a synonym of Rumex longifolius DC..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50079670) with original publication details: Novit. Fl. Suec. Alt. 106 1828.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:697189-1.
This name was in version 1 of The Plant List, record tro-50079670, and has not been changed.