1. Ionactis linariifolius (L.) Greene (stiff aster, stiff-leaved aster, flax-leaved aster)

Aster linariifolius L.

Pl. 229 a, b; Map 989

Plants perennial herbs, with a short, thick, somewhat woody rootstock, rarely also with slender rhizomes. Stems 1 to several, 10–50(–70) cm long, erect or ascending from a sometimes somewhat spreading base, usually unbranched, nearly smooth or with fine, longitudinal lines, nearly glabrous or sparsely pubescent with minute, curled hairs toward the base, moderately to densely and minutely hairy toward the tip. Basal leaves absent at flowering. Stem leaves more or less uniform in size and spacing, 1–4 cm long, 0.5–4 mm wide, linear or very narrowly oblong-oblanceolate, stiff and somewhat leathery, narrowed or short-tapered to a sharply pointed tip, abruptly rounded to a sessile, nonclasping base, the margins entire, the surfaces glabrous (the upper surface often somewhat shiny), the margins strongly roughened with moderate to dense, minute, stiff, triangular hairs. Inflorescences of solitary heads or racemes with relatively few heads, but rarely somewhat branched and appearing as rounded to flat-topped panicles of up to 30 heads, the heads nearly sessile to long-stalked, the bracts relatively dense, 0.3–1.2(–2.5) cm long, herbaceous but noticeably shorter than the adjacent leaves, linear. Heads radiate, not sticky or resinous. Involucre 6–9 mm long, cup-shaped to somewhat obconical. Involucral bracts in 4–7 unequal, overlapping series, oblong-lanceolate to lanceolate-triangular, the tip ascending, with a thickened, slender, green central band that is broadened and narrowly elliptic toward the tip (the green color sometimes absent below the midpoint), the broad, lighter margins often with a purple border, especially toward the tip, the margins appearing finely hairy, especially toward the tip, the outer surface glabrous. Receptacle flat or shallowly convex, with minute, irregular ridges around the concave attachment points of the florets. Ray florets 6–20, pistillate, the corolla 5–12 mm long, lavender to purple (rarely white elsewhere). Disc florets 20–40, perfect, the corolla 4–7 mm long, relatively deeply lobed (0.3–0.7 mm), yellow, sometimes turning reddish purple after the pollen has been shed, not persistent at fruiting. Pappus of the ray and disc florets similar, of 2 types, an inner series of numerous finely barbed bristles 4–7 mm long, these not broadened toward the tip, and an outer series of fewer but still relatively numerous bristles 0.2–0.8 mm long, both series straw-colored to light orangish tan. Fruits 2.0–3.5 mm long, narrowly obconical, somewhat 4–6-angled, the angles with yellowish brown ribs, densely silky-hairy, dark brown to purplish brown. 2n=18. August–November.

Scattered in the Ozark and Ozark Border Divisions (eastern U.S. west to Wisconsin, Kansas, and Texas; Canada). Mesic to dry upland forests (usually on rocky slopes), savannas, ledges of bluffs, and margins of glades; also roadsides.

Steyermark (1963) noted that this attractive clump-forming species was a desirable addition to rock gardens but that it required acidic soils for best growth. In recent years, it has become available commercially through native plant nurseries. White-rayed plants that eventually may be found in Missouri have been called f. leucactis Benke.