1. Thymelaea passerina (Linnaeus) Cosson & Germain, Syn. Anal. Fl. Paris ed. 2. 360. 1859.
Passarine annuelle, spurge flax Passarine annuelle, spurge flax
Stellera passerina Linnaeus, Sp. Pl. 1: 559. 1753
Stems green or yellow-green, turning red in fall. Leaves upright; petiole to 1 mm; blade 0.6–1.5 × 0.1–0.2 cm, stiff, herbaceous to coriaceous, apex acute. Inflorescences cymose, 1–7-flowered; bracts 1.5 cm, with tuft of white trichomes at base. Flowers: hypanthium green to yellow, tubular, becoming urceolate, 2–3 mm, appressed-hairy; calyx lobes minute; stamens: distal whorl inserted at throat; distal anthers subexserted; ovary 0.75 mm, apex hairy; style 0.7–0.8 mm, glabrous, becoming ± eccentric in fruit; stigma exserted. Capsules pyriform. 2n = 18.
Flowering summer (late Jun–Aug); fruiting summer–fall (Jul–early Sep). Dry, disturbed ground, including prairies and old fields; 10–300 m; Ont., Que.; Ala., Ill., Iowa, Kans., Mich., Miss., Nebr., Ohio, Tex., Wash., Wis.; s Europe; Mediterranean regions.
Thymelaea passerina is sometimes accidentally introduced in fodder and spreads quickly. It is sometimes mistaken for one of the delicate species of Polygala.