Western Silver Aster

Symphyotrichum sericeum is known in the Bahamas as S. lucayanum (Britton) G. L. Nesom [syn. Aster lucayanus Britton, Virgulus lucayanus (Britton) Reveal & Keener]. It is of conservation concern in Indiana, Michigan, and Canada. Symphyotrichum sericeum is distinct and unlikely to be confused with other species due to its silvery-silky leaves and phyllaries, open arrays, and cormoid rootstocks. Aster sericeus forma albiligulatus Fassett is a white form of the species, in contrast to the typically purple forma sericeus; these do not deserve formal recognition.

Perennials, (20–)30–70 cm, cespitose, eglandular; with short, woody, cormoid caudices, or short rhizomes. Stems 1–5+, ascending to erect (thin, grayish brown to dark brown), glabrous proximally, densely canescent distally. Leaves (silvery) firm, soft; basal withering by flowering, sessile, blades (1–3 nerved) elliptic-lanceolate, 10–40 × 5–15 mm, bases cuneate, weakly sheathing, margins usually entire, rarely remotely serrate, piloso-ciliate, apices acute, faces less copiously hairy than cauline; proximal cauline withering by flowering, sessile, blades oblanceolate or oblong to linear-lanceolate, 15–30(–50) × 4–10 mm, slightly and progressively reduced distally, bases rounded, sub­clasping, margins entire, silky-pilose, apices obtuse to acute, mucronulate, faces sparsely to densely silky-pilose; distal sessile, blades lanceolate, 10–30 × 5–8 mm, little reduced distally, bases cuneate, margins entire, apices acute, mucronate, faces ± densely silky. Heads in open, paniculiform arrays, branches sparse, fastigiate, often arching (1–5+ per branch). Peduncles subsessile or 0.5–3(–5) cm, densely sericeo-strigose, bracts crowded, 4–8(–10) mm, grading into phyllaries. Involucres campanulate to cylindric, (5–)7.5–10 mm. Phyllaries in 3–5(–6) series, outer ovate with expanded distal portion [(4–)5–6 mm], mid ovate-lanceolate [6–8(–10) mm] with expanded green portions, inner linear, unequal or sometimes subequal, outer often foliaceous, bases (mid) scarious, margins silky, green zones restricted to expanded distal ¹ / 2 – ² / 3 (obscured by hairs), apices (outer) spreading or squarrose to reflexed, acute, mucronulate, faces densely long-silky. Ray florets (10–)15–30; corollas usually rose-purple to deep purple, rarely white, laminae 8.5–11 × 1–1.5 mm. Disc florets (15–)25–35; corollas pink turning purple, (5–)5.5–7 mm, tubes shorter than narrowly funnelform throats (both thinly puberulent), lobes deltate, 0.7–0.9 mm. Cypselae purple or brown, obovoid, not compressed, 2–3 mm, 7–10-nerved (prominent), faces glabrous; pappi whitish or tawny, 6–7 mm. 2n = 10, 20.

Aster sericeus Ventenat, Descr. Pl. Nouv., plate 33. 1800; Lasallea sericea (Ventenat) Greene; Virgulus sericeus (Ventenat) Reveal & Keener

When biologist Diana Bizecki Robson sits in the middle of the tallgrass prairie in a park near Winnipeg, she sees stars—the tiny, bright flowers of the western silvery aster. The prairie may seem a world away from our modern lives, but Robson shows how this endangered ecosystem’s flora and fauna are intimately connected with our own well-being.

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The Western Silver Aster, Symphyotrichum sericeum, is one of many organisms found in the endangered tallgrass prairies of Winnipeg, Canada.The aster is a food source for insects in the prairie and the insects provide cross-pollination for the flowers.Both are critical for the survival of this ecosystem.

Host Ari Daniel Shapiro speaks with Diana Bizecki Robson of the Manitoba Museum about how this endangered ecosystem’s flora and fauna are intimately connected with our own well-being.

Symphyotrichum sericeum (formerly Aster sericeus) is a species of flowering plant in the family Asteraceae native to central North America. Commonly known as western silver aster, western silvery aster, and silky aster, it is a perennial, herbaceous plant that may reach 70 centimeters (2+1⁄4 feet) tall. Its flowers have purple ray florets and pink then purple disk florets, and its leaves are firm and silvery-green.