Rheum undulatum var. longifolium Metzg. Dataset GBIF Backbone Taxonomy Rank VARIETY Classification kingdom Plantae phylum Tracheophyta class Magnoliopsida order Caryophyllales family Polygonaceae genus Rheum species Rheum rhabarbarum Name Homonyms Rheum undulatum var. longifolium C.Y.Cheng & T.C.Kao Rheum undulatum var. longifolium Metzg. ex Alef. Rheum undulatum var. longifolium Metzg.