It has been recommended that Polygonella be included within Polygonum, as they share dimorphic tepals with a single main vein, sinuate-margined epidermal tepal cells, irregularly ridged cuticle, and filaments with a dilated base and the outer shorter than the inner ones (Ronse De Craene et al. 2004; Schuster et al. 2011, 2015). Plastid sequences have provided support for uniting Polygonella with Polygonum, although nuclear data (ITS) have so far not resolved the relationships.