Methodus, 290. 1794.
Stems ascending or erect, green or striped with pink or red, branched, (7–)15–90 cm. Leaves: ocrea brownish hyaline, loose, funnelform, 2–8 mm, margins truncate, eciliate, glabrous or puberulent proximally; petiole 1.5–6(–9) cm, usually puberulent adaxially; blade palmately veined with 7–9 primary basal veins, hastate-triangular, sagittate-triangular, or cordate, 2.5–8 × 2–8 cm, base truncate or cordate to sagittate, margins ciliolate, apex acute to acuminate. Inflorescences terminal and axillary, paniclelike, 1–4 cm, usually crowded at stem apices; peduncle 0.5–4 cm, puberulent in lines. Pedicels ascending or recurved, 2.5–4 mm. Flowers chasmogamous, heterostylous [homostylous]; perianths creamy white to pale pink; tepals elliptic to obovate, (2.5–)3–5 mm, margins entire, apex obtuse to acute; stamens ca. 1/2 as long as or slightly longer than perianth; styles 1.5–2 mm or 0.5–1 mm; stigmas purplish. Achenes uniformly light brown or streaked with dark brown or black, sharply 3-gonous, 4–6 × 4–6 mm, faces smooth, angles prominent, unwinged or essentially so, smooth or occasionally with blunt tooth in proximal 1/3. 2n = 16 (China).
Phenology: Flowering Jun–Sep; fruiting Jun–Nov.
Habitat: Cultivated as crop plant, waif along railroads, roadsides, fields, waste places, occasionally weedy
Elevation: 0-2200 m
Introduced; Alta., Man., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Sask., Yukon, Ala., Alaska, Ariz., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., Wash., W.Va., Wis., Wyo., Asia (China), introduced in Central America, South America, Europe, Asia, Africa.
Fagopyrum esculentum is a heterostylous, obligate out-crosser. Morphological, allozyme, and molecular data suggest that the cultivated plants are most closely related to wild ones in northwestern Yunnan, China.
Common buckwheat is an important pseudocereal crop in China, the Russian Federation, Ukraine, Kazakhstan, and Poland; it is grown in many other countries. It is planted frequently in wildlife food plots, as a catch or cover crop, and as a honey plant in North America. Hulls from the achenes are used for pillow filling, which manufacturers claim has health benefits over traditional foam, polyester, or down fillings.