21. Symphyotrichum sericeum (Vent.) G.L. Nesom (silky aster)

Aster sericeus Vent.

Pl. 249 a–c; Map 1033

Plants perennial herbs, usually with a short, stout, cormlike rootstock, this somewhat woody, sometimes more elongate and rhizomatous. Stems 1 to several, 30–70 cm long, with few to several ascending to loosely ascending branches above the midpoint, ranging from glabrous or nearly so toward the base to densely pubescent with appressed, silky hairs toward the tip. Basal as well as lower to median stem leaves absent at flowering, sessile, the blade 1.5–5.0 cm long, 0.4–1.0 cm wide, mostly oblanceolate to oblong-elliptic, short-tapered to rounded at the base, mostly angled and with a minute, sharp point at the tip, the margins entire, the margins and surfaces moderately to densely pubescent with appressed, silky hairs (the leaves appearing gray or silvery), the secondary veins on the leaf undersurface not visible or faint and few. Median and upper stem leaves relatively uniform, sessile, not clasping or sheathing the stem, the blades 0.7–3.0 cm long, lanceolate or elliptic, angled or rounded at the base, otherwise similar to the lower stem leaves. Inflorescences sometimes appearing as open panicles but more often appearing as solitary heads or small clusters at the branch tips, the heads appearing short- or less commonly long-stalked, the bracts similar to the adjacent foliage leaves. Heads mostly 2–3 cm in diameter (including the extended ray corollas) at flowering. Involucre 6–10 mm long, the bracts in 3–6 unequal, overlapping series. Involucral bracts lanceolate to ovate, angled or short-tapered at the sharply pointed tip, the tip erect or ascending, the green, leaflike portion in the apical 1/2–2/3 abruptly contracted (sometimes only slightly narrower) to the pale, thickened, yellowish basal portion, the outer surface and margins densely appressed-hairy. Ray florets 10–25 in usually 1 series, the corollas well developed, 9–15 mm long, dark purple or nearly blue. Disc florets 15–35, the corollas 5–7 mm long, minutely hairy, the slender portion of the tube much shorter than the slightly expanded apical portion, the lobes 0.7–0.9 mm long, 18–22 percent of the total length of the expanded portion. Pappus bristles 5.5–7.0 mm long, often slightly longer than the disc corollas, off-white to cream-colored or tan. Fruits 2–3 mm long, with 7–10 longitudinal ribs, purplish brown to brown, glabrous. 2n=10. August–October.

Scattered in the Ozark, Ozark Border, and Unglaciated Plains Divisions, north locally to Lincoln County and along the Missouri River to Atchison County (North Dakota to Texas east to Michigan, Indiana, and Arkansas; disjunct in Georgia). Glades, upland prairies, and loess hill prairies.

This beautiful wildflower is available for sale at some wildflower nurseries and should be used more widely in gardens. The white-rayed Aster sericeus f. albiligulatus Fassett has not yet been found to grow in Missouri.