14. Symphyotrichum oolentangiense (Riddell) G.L. Nesom (azure aster, blue devil)

Aster oolentangiensis Riddell

A. azureus Lindl. ex Hook.

Pl. 244 g, h; Map 1026

Plants perennial herbs, usually from a short, stout, somewhat branched rootstock, this sometimes somewhat woody, occasionally also producing short rhizomes. Stems 1 to few, 30–120 cm long, unbranched or with few to several ascending branches above the midpoint, glabrous or sparsely to moderately roughened with short, spreading hairs in longitudinal lines or bands, mostly toward the stem tip. Basal and/or lower stem leaves present at flowering, long-petiolate, the petiole sometimes narrowly winged (often only toward the tip), the blade 4–18 cm long, 1–5 cm wide, heart-shaped or occasionally ovate, deeply cordate to less commonly truncate or abruptly rounded at the base, angled or tapered to a sharply pointed tip, the margins entire or with a few minute, widely spaced teeth, moderately to densely roughened with minute, stiff hairs on the upper surface, densely pubescent with slightly longer (still somewhat sandpapery) hairs on the undersurface, the secondary veins on the leaf undersurface faint or sometimes easily observed, often irregularly fused toward their tips, the veinlets often indistinct, forming a dense, irregular network of relatively short areoles. Median and upper stem leaves progressively smaller, with long to short, often winged but not clasping or sheathing petioles or the uppermost leaves sessile, the blades 1–6 cm long, narrowly ovate to narrowly lanceolate, rounded to tapered at the base, otherwise similar to the lower stem leaves. Inflorescences usually panicles with relatively long, loosely ascending, few-headed, racemose branches, sometimes with denser heads along the branches or reduced to a solitary raceme, the heads appearing short- or long-stalked, the bracts along the ultimate branches 0.3–0.8(–1.2) cm long, leaflike, mostly linear, noticeably shorter and narrower than the adjacent foliage leaves. Heads mostly 1.5–2.5 cm in diameter (including the extended ray corollas) at flowering. Involucre 4.5–8.0 mm long, the bracts in 4–6 unequal, overlapping series. Involucral bracts linear to narrowly lanceolate or narrowly oblong, angled or short-tapered at the mostly sharply pointed tip, the tip erect or ascending (the lowermost bracts occasionally slightly spreading), the slender midvein broadened relatively abruptly in the apical 1/5–1/3 (rarely more) into an elliptic or broadly diamond-shaped (up to 2.5 times as long as wide) green tip, the outer surface glabrous or sparsely short-hairy, the margins moderately hairy, especially toward the tip. Ray florets 10–25 in 1 or 2 series, the corollas well developed, 6–12 mm long, lavender to purple to blue, rarely pink or white. Disc florets 15–28, the corollas 4–5 mm long, the slender portion of the tube shorter than the slightly expanded apical portion, the lobes 0.4–0.7 mm long, 20–25 percent of the total length of the expanded portion. Pappus bristles 3.5–5.0 mm long, off-white to pale cream-colored, occasionally purplish-tinged. Fruits 1.5–2.0 mm long, mostly with 4 longitudinal ribs, purplish brown (rarely tan) often with lighter ribs, glabrous or sparsely hairy. 2n=32. August–November.

Scattered nearly throughout the state (South Dakota to Texas east to New York, Ohio, and Florida; Canada). Glades, upland prairies, sand prairies, savannas, mesic to dry upland forests on rocky slopes, and ledges and tops of bluffs; also roadsides.

This species was long known under the name Aster azureus until A. G. Jones (1983) resurrected the slightly older name A. oolentangiensis. This epithet represents a noncorrectable misspelling of the place where the species was first discovered, the Olentangy River in Ohio. Several authors have noted that it is closely related to Symphyotrichum laeve (Semple et al., 2002), and apparent rare hybrids between the two have been reported (Steyermark, 1963).

Variation within S. oolentangiensis is complex and some botanists prefer not to recognize infraspecific taxa within the species (Gleason and Cronquist, 1991). Plants with glabrous stems have sometimes been segregated as A. oolentangiensis var. laevicaulis (a name that has not been transferred to Symphyotrichum), but this feature occurs in both of the varieties accepted below. When plants have hairy stems, the density of pubescence in Missouri populations varies from nearly glabrous to fairly densely hairy. It thus seems best not to attempt formal taxonomic recognition of pubescence variants.