1. Soliva sessilis Ruiz & Pavón, Syst. Veg. Fl. Peruv. Chil. 113, plate 24. 1798.
Field burrweed, lawn burweed
Soliva daucifolia Nuttall; S. pterosperma (Jussieu) Lessing
Plants (1–)2–5(–25+) cm (high or across), ± villous, glabrescent (not stoloniferous, stems purplish, prostrate to ascending, often rooting at nodes). Leaves basal and cauline; blades ± oblanceolate, 1–2(–3)+ cm, 2(–3)-pinnati-palmately lobed. Heads mostly scattered along stems. Involucres 2–4(–5) mm diam. Pistillate florets 5–8(–17+) in 1–2+ series. Disc florets 4–8+; corollas 1.5–2.5 mm. Cypselae: bodies ± obovate to lanceolate, (1.5–)2.5–3+ mm, usually winged (wings entire or ± sinuate to incised, each shoulder usually distally projecting as spinelike tooth), faces glabrous or ± scabrellous to hirtellous; pappi 0 (persistent stylar sheaths indurate, spinelike, 1–2+ mm, erect or slightly inflexed). 2n = ca. 92 (as S. pterosperma), 110+ (from Portugal), 118–120.
Flowering Mar–Jun(–Dec). Disturbed sites, lawns, roadsides; 0–600 m; introduced; B.C.; Ala., Ark., Calif., Fla., Ga., La., Miss., N.C., Okla., Oreg., S.C., Tex., Va., Wash.; South America; introduced also in Europe.