American jointweed, southern jointweed

Gonopyrum americanum Fischer & C. A. Meyer, Mém. Acad. Imp. Sci. Saint-Pétersbourg, Sér. 6, Sci. Math., Seconde Pt. Sci. Nat. 4: 144. 1840

Subshrubs, perennial, synoecious, 5.5-9 dm. Stems erect, branched proximally and basally, glabrous. Leaves persistent; ocrea margins not ciliate; blade linear to spatulate, (4-)5-12(-19) × 0.5-0.9(-1.2) mm, base barely tapered, margins not hyaline, apex obtuse to acute, often erose, glabrous. Inflorescences (7-)18-30(-60) mm; ocreola encircling rachis, only the base adnate to rachis, apex acuminate. Pedicels spreading in anthesis and fruit, 0.4-2.3 mm, usually much longer than subtending ocreola. Flowers bisexual; outer tepals sharply reflexed early in anthesis and in fruit, white to pink, elliptic to ovate, 1.2-2.2 mm in anthesis, margins erose; inner tepals loosely appressed in anthesis and fruit, white to pink, ovate to subor-biculate, 1.7-2.9 mm in anthesis, margins erose; filaments dimorphic; anthers yellow or pink; styles and stigmas 0.5-1 mm in anthesis. Achenes included, reddish brown, 3(-4)-gonous, 2.5-4 × 1.3-2.3 mm, shiny, smooth. 2n = 36.

Flowering Jun-Oct. Sandy roadsides, fields, riverbanks, scrub forests, waste places; 10-200 m; Ala., Ark., Ga., La., Mo., N.Mex., Okla., S.C., Tex.