Tall flat-topped white aster, parasol whitetop, aster à ombelle

Aster umbellatus Miller, Gard. Dict. ed. 8, Aster no. 22. 1768; Diplopappus umbellatus (Miller) Hooker; Diplostephium umbellatum (Miller) Cassini

Plants 50–200 cm (short to long-rhizomatous, sometime colonial). Stems 1–10(–20), ascending to erect, striate, glabrous or sparsely hairy. Cauline leaves: mid and distal crowded, blades broadly to narrowly elliptic, (35–)60–110(–150) × (5–) 13–25(–35) mm, ± reduced distally, not stiff, bases attenuate, margins entire, involute, finely ciliate, apices acuminate, faces glabrous or sparsely hairy, especially along veins abaxially, or densely hairy. Heads (3–)20–100(–300+). Peduncles 1–10 mm, moderately to densely canescent; bracts linear-lanceolate to elliptic. Involucres 3–5 mm. Phyllaries in 3–4 series, triangular-lanceolate, midveins not swollen, apices finely subulate, strigose. Rays (2–)5–10(–16); laminae (4–)7–10(–12.3) × (0.8–) 1.2–1.8(–2.7) mm. Disc florets (5–)11–26(–50); corollas 3.5–6 mm, lobes 2–3.2 mm, 60–75% of limb. Cypselae 1.4–3.2 mm, 4–6-ribbed, sparsely to densely strigose; pappi: outer 0.2–0.8 mm, inner 3.5–6.2 mm. 2n = 18.

Varieties 2 (2 in the flora): e North America.