Phylum Magnoliophyta Cronquist, Takht. & Zimmerm. ex Reveal (1996) see Infraphylum Angiospermae auct.
   Class Magnoliopsida Brongn. (1843)
     Subclass Caryophyllidae Takht. (1967) see Order Caryophyllales Juss. ex Bercht. & J.Presl (1820)
       Superorder Polygonanae Takht. ex Reveal (1992) see Order Caryophyllales Juss. ex Bercht. & J.Presl (1820)
         Order Polygonales Dumort. (1829) see Order Caryophyllales Juss. ex Bercht. & J.Presl (1820)
           Family Polygonaceae Juss. (1789), nom. cons. - buckwheat family
             Subfamily Eriogonoideae Arn.
               Tribe Pterostegieae
                 1 Genus Pterostegia F.E.L. Fisch. & C.A.Mey. (1835)
                 2 Genus Harfordia E.L. Greene & C.C. Parry (1886)