Sp. Pl. 2: 630. 1753.
Biennials; blackening upon drying. Stems simple or branched distally, 3–9 dm, spreading-hirsute proximally, appressed-hirsute or glabrous distally. Leaves much smaller distally; larger blade: major veins 3, minor veins (0–)2, narrowly ovate to lanceolate, 25–65 x 5–18 mm, margins irregularly dentate, teeth 2–3 mm, apex acute, surfaces short-hispid. Spikes: bracts ovate-lanceolate, 4–6 mm. Pedicels 1–1.5 mm; bracteoles 2–3 mm. Flowers: calyx 6–8 mm, tube obscurely 10-nerved, ascending- to appressed-hispid, hairs often pustular-based; corolla 15–21 mm, glabrate externally, lobes 5–8 mm; style included, 1–2 mm. Capsules blackish, ovoid, 6–8 mm, glabrate. Seeds 0.6–0.8 mm. 2n = 40.
Phenology: Flowering May–Oct.
Habitat: Moist to dry prairies, prairie openings, barrens, glades, pine savannas, interdune pannes.
Elevation: 20–400 m.
Ont., Ala., Ark., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va.
Buchnera americana has declined significantly in the past century and now is of conservation concern in most states east of the Mississippi River and in Ontario; its current stronghold is in Kansas, Missouri, and Oklahoma. In greenhouse studies, B. americana and B. floridana parasitized a variety of grass and tree species (Celtis, Fraxinus, Liquidambar, Liriodendron, Nyssa, Paspalum, Pinus, Quercus); natural hosts remain largely undocumented (L. J. Musselman and W. F. Mann 1977, 1978). It is nearly restricted to older geological regions away from the coastal plain, primarily in circumneutral to high pH soils; there are records from eastern Texas-central Louisiana, southeastern Louisiana-southern Mississippi, and a few records from northwestern Florida, all apparently in acidic soils. There appears to be no morphological intergradation with B. floridana in those areas, and the occurrence of B. americana there is puzzling.