Herbs, annual; taprooted. Stems erect or ascending, glabrous or puberulent. Leaves deciduous, cauline, alternate, petiolate (proximal leaves) or sessile (distal leaves); ocrea persistent or deciduous, chartaceous; petiole base articulated; blade cordate, triangular, hastate, or sagittate, margins entire to sinuate. Pedicels present. Inflorescences axillary, or terminal and axillary, racemelike or paniclelike, pedunculate. Flowers bisexual or, rarely, bisexual and staminate on same plant, 2–6 per ocreate fascicle, heterostylous or homostylous, base stipelike; perianth nonaccrescent, white, pale pink, or green, broadly campanulate, glabrous; tepals 5, distinct, petaloid, dimorphic, outer smaller than inner; stamens 8; filaments distinct, free, glabrous; anthers white, pink, or red, oval to elliptic; styles 3, reflexed, distinct; stigmas capitate. Achenes strongly exserted, brown to dark brown or gray, sometimes mottled black, unwinged or essentially so, bluntly to sharply 3-gonous, glabrous. Seeds: embryo folded. x = 8.

Distribution

Eurasia, e Africa, introduced elsewhere, cultivated in temperate regions worldwide.

Discussion

Species 16 (2 in the flora).

Fagopyrum esculentum and F. tataricum are cultivated widely. In North America, they often escape, but populations generally are ephemeral.

Archaeological evidence for the cultivation of buckwheat dates to 4600 bp in China and 3500 bp in Japan (O. Ohnishi 1998). Molecular studies indicate that Fagopyrum comprises two major clades, with F. esculentum and F. tataricum in the large-fruited “cymosum” group (O. Ohnishi and Y. Matsuoka 1996; Y. Yasui and O. Ohnishi 1998, 1998b; O. Ohsako and O. Ohnishi 2000).

Selected References

Ohnishi, O. and Y. Matsuoka. 1996. Search for the wild ancestor of buckwheat II. Taxonomy of Fagopyrum (Polygonaceae) species based on morphology, isozymes and cpDNA variability. Genes Genet. Systems 71: 383–390.

Ohnishi, O. 1998. Search for the wild ancestor of buckwheat III. The wild ancestor of cultivated common buckwheat, and of Tartary buckwheat. Econ. Bot. 52: 123–133.

Ohsako, T. and O. Ohnishi. 2000. Intra- and interspecific phylogeny of wild Fagopyrum (Polygonaceae) species based on nucleotide sequences of noncoding regions of chloroplast DNA. Amer. J. Bot. 87: 573–582.

Yasui, Y. and O. Ohnishi. 1998. Phylogenetic relationships among Fagopyrum species revealed by the nucleotide sequences of the ITS region of the nuclear rRNA gene. Genes Genet. Systems 73: 201–210.

Yasui, Y. and O. Ohnishi. 1998b. Interspecific relationships in Fagopyrum (Polygonaceae) revealed by the nucleotide sequences of the rbcL and accD genes and their intergenic region. Amer. J. Bot. 85: 1134–1142.

Lower Taxa

Fagopyrum esculentum, Fagopyrum tataricum

Key

1	Achene faces smooth, angles smooth; tepals (2.5-)3-5 mm; perianths, creamy white topale pink; inflorescences paniclelike, 1-4 cm, terminal and axillary	Fagopyrum esculentum
1	Achene faces irregularly rugose, angles often sinuate-dentate; tepals 1.5-3 mm; perianths,green with whitish margins; inflorescences racemelike, 2-10 cm, axillary	Fagopyrum tataricum