⚠ Version 1 of The Plant List has been superseded.
This name record (from Tropicos) is not included in version 1.1 of The Plant List. It is possible the same name is included from a different data source, to check this you can search for Sium longifolium in version 1.1 of The Plant List.
This name is a synonym of Oxypolis rigidior var. longifolia .
The record derives from Tropicos which reports it as a synonym (record 50086057
) with original publication details: Fl. Amer. Sept. 1: 194 194 1814.
Full publication details for this name can be found in IPNI: urn:lsid:ipni.org:names:849018-1
.