Southwestern annual saltmarsh aster

Tripolium subulatum (Michaux) de Candolle var. parviflorum Nees, Gen. Sp. Aster., 157, 286. 1833; Aster subulatus Michaux var. cubensis (de Candolle) Shinners; Erigeron expansus Poeppig ex Sprengel; Symphyotrichum expansum (Poeppig ex Sprengel) G. L. Nesom

Plants (10–)70–150 cm. Stems usually simple, often with short, leafy branches proximally. Heads 20–100, in open, diffuse arrays, primary branches longer than peduncles. Involucres 5–6.2 mm. Phyllaries 30–42, sub-ulate to lanceolate, narrow, green zones narrowly lanceolate. Ray florets (23–)27–37(–42) in (1–)2 series; laminae usually white, sometimes pink, 1.9–3 × 0.2–0.5 mm, longer than pappi, drying in 1–2 coils (apices shallowly to deeply lobed). Disc florets (6–)8–15; corollas 3.4–4.4(–4.7) mm. Cypselae 1.5–2.7 mm; pappi 3.5–3.8(–4.2) mm. 2n = 10.

Flowering Jul–Nov(–Jan). Roadsides, marshy habitats, often weedy; 0–1100(–4000) m; Ala., Ariz., Calif., Fla., Nev., N.Mex., Okla., Tex., Utah; Mexico; West Indies; Central America; n South America; introduced in Asia (Japan), Pacific Islands (Hawaii).