This name is a synonym of Rumex lacustris Greene.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 26001671) with original publication details: Madroño 31(4): 252 1984.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:923806-1.
This name was in version 1 of The Plant List, record tro-26001671, and has not been changed.