Tradescant's American Aster

In Great Britain and/or Ireland:
Foodplant / parasite
Golovinomyces orontii parasitises live Aster tradescantii

Perennials, 5–70 cm, cespitose; short-rhizomatous. Stems 1–5+, ascending to erect (straight, slender, 1–2.5(–3) mm diam.), glabrous. Leaves thin, margins scab­rous to scabrellous or eciliate, apices mucronulate, faces gla­brous; basal persistent or withering by flowering, petiolate (petioles slightly winged, sheathing), blades spatulate to elliptic or oblanceolate, 10–40 × 5–11 mm, bases cuneate to attenuate, margins crenate-serrate, apices obtuse to acute; proximal cauline persistent or withering by flowering, ± broadly winged-petiolate or sessile, blades oblong, lanceolate or elliptic-lanceolate to oblanceolate, or linear-lanceolate, 20–100 × 3–9 mm, bases attenuate to cuneate, slightly clasping, margins serrulate or entire; distal sessile, blades oblanceolate to linear-lanceolate or linear, 10–60 × 1–7 mm, gradually reduced distally, bases cuneate to tapering, margins serrulate or entire, apices acute to acuminate. Heads {(10–)25–100} in paniculiform arrays, branches ascending (1–10 heads per branch). Peduncles ascending, 0.2–2.5+ cm, glabrous, bracts 1–4, subulate to linear. Involucres cylindro-campanulate, 3.3–4.5(–5) mm. Phyllaries in 4–5 series oblong-lancoelate (outer) to linear-lanceolate (inner) or linear (innermost), unequal, bases indurate ¹ / 2 +, margins scarious, erose, hyaline, ciliolate, green zones lanceolate, apices acute to acuminate or caudate, mucronulate or apiculate, sometimes purplish, faces glabous. Ray florets 14–27; corollas white, laminae 4.3–8.2 × 0.7–0.8 mm. Disc florets 20–30; corollas pale yellow becoming purplish, 3–4.1 mm, tubes shorter to nearly equaling funnelform throats, lobes lanceolate, 0.5–1 mm. Cypselae tan (nerves stramineous), obovoid, ± compressed, 3.5–4 mm, 4–5-nerved, faces strigillose; pappi white, 3–3.6 mm. 2n = 16, 32.

Aster tradescantii Linnaeus, Sp. Pl. 2: 876. 1753 (as tradescanti)

Symphyotrichum tradescantii (formerly Aster tradescantii) is a species of flowering plant in the family Asteraceae native to northeastern North America. Common names include Tradescant's aster and shore aster.