12. Symphyotrichum oblongifolium (Nutt.) G.L. Nesom (aromatic aster, oblong-leaved aster)

Aster oblongifolius Nutt.

A. oblongifolius var. angustatus Shinners

Pl. 249 f, g; Map 1024

Plants perennial herbs, with a somewhat woody, horizontal rootstock, often also with 1 or more slender and longer-creeping, rhizomatous branches. Stems 1 several, 15–80 cm long, with few to more commonly several ascending to spreading branches above the midpoint, sparsely to moderately and usually evenly pubescent with short, spreading hairs, progressively more glandular toward the tip, the branches and apical portion of the main stem usually with dense, stalked glands. Basal and lower stem leaves absent at flowering, sessile or nearly so, the blade 2–6 cm long, 0.5–1.5 cm wide, oblanceolate, tapered at the base, rounded or angled to a usually bluntly pointed tip (sometimes abruptly tapered to a minute, sharp point), the margins entire and hairy, the surfaces usually sparsely pubescent with short, loosely ascending to spreading hairs and also usually sparsely glandular, appearing more or less 3-veined, the secondary veins on the leaf undersurface often relatively faint, strongly ascending parallel to the midvein, often fused irregularly toward the tip, the veinlets forming a dense, irregular network of relatively short to somewhat elongate areoles. Median and upper stem leaves often relatively numerous, more or less progressively smaller toward the stem tip, sessile, not clasping the stem (a few of the larger leaves sometimes slightly clasping, the blades 1–10 cm long, narrowly oblong-lanceolate to narrowly lanceolate, rarely broader, narrowed or rounded at the sometimes slightly expanded base, occasionally appearing truncate, angled or tapered to a bluntly or sharply pointed tip, the margins entire, hairy, the surfaces moderately to densely hairy, those of the upper leaves also with moderate to dense, stalked glands, the venation often faint, sometimes more or less with 3 main veins. Inflorescences usually appearing as open panicles, sometimes with solitary heads or small clusters at the tips of short to long branches, the heads appearing mostly long-stalked, the bracts few to several, 0.3–0.8 cm long, linear to narrowly oblong. Heads 2–3 cm (broader in some cultivars) in diameter (including the extended ray corollas) at flowering. Involucre 5–8 mm long, the bracts in 4–6 subequal to somewhat unequal, overlapping series. Involucral bracts mostly narrowly oblong to narrowly oblong-oblanceolate, all but the inner series angled or short-tapered to the sharply pointed tip, the tip spreading or reflexed, those of the outer series often more or less leaflike, the green portion extending more than 2/3 of the way to the base, those of the other series with a somewhat thickened and keeled base having a slender, green midvein that is expanded abruptly in the apical 1/3–1/2 into an oblong to elliptic, green apical area, sometimes purplish-tinged, the surfaces and margins with relatively dense, stalked glands. Ray florets 15–35 in usually 1 or 2 series, the corollas well developed, 9–15 mm long, reddish purple to bluish purple, rarely pink. Disc florets 30–50, the corollas 4.5–6.0 mm long, the slender portion of the tube usually slightly shorter than the slightly expanded apical portion, the lobes 0.4–0.7 mm long, 18–25 percent of the total length of the expanded portion. Pappus bristles 4–6 mm long, mostly pale orangish brown to light tan, occasionally purplish-tinged. Fruits 2.0–2.5 mm long, with 7–10 longitudinal ribs, purplish brown to brown, sparsely hairy. 2n=10, 20. July–November.

Scattered, mostly south of the Missouri River, but extending northward locally mostly in counties adjacent to the Mississippi and Missouri Rivers and apparently absent from the Mississippi Lowlands Division (eastern U.S. [except a few southeastern states] west to Montana and New Mexico). Glades, ledges and tops of bluffs, upland prairies, and openings of dry upland forests; also railroads.

Rare plants with pink ray corollas have been called Aster oblongifolius f. roseoligulatus (Benke) Shinners. Semple and Ford (1981) studied variation in leaf morphology in this species and S. novae-angliae (both as species of the segregate genus Lasallea Greene) and concluded that there was no statistical basis for the taxonomic recognition of varieties described from leaf size and shape extremes in either species.

A putative hybrid between this species and S. ericoides has been called S. Hbatesii (Rydb.) G.L. Nesom (Nesom, 1994) and was originally described from Nebraska. It may be found eventually in Missouri, possibly in the northwestern portion of the state where these two species occur in proximity.