3. Symphyotrichum cordifolium (L.) G.L. Nesom (blue wood aster)

Aster cordifolius L.

A. sagittifolius Wedem. ex Willd.

A. cordifolius ssp. sagittifolius (Wedem. ex Willd.) A.G. Jones

A. cordifolius var. polycephalus Porter

S. cordifolium var. polycephalum (Porter) G.L. Nesom

Pl. 244 c, d; Map 1015

Plants perennial herbs, usually from a short, stout, somewhat branched rootstock, this sometimes somewhat woody, often also producing elongate rhizomes. Stems 1 to several, 25–120 cm long, unbranched or with few to several ascending branches above the midpoint, glabrous or sparsely to moderately pubescent toward the tip with short, curled hairs in longitudinal lines or bands. Basal and/or lower stem leaves usually present at flowering, long-petiolate, the petiole unwinged or less commonly very narrowly winged, the blade 4–13 cm long, 1–6 cm wide, narrowly to broadly heart-shaped, deeply cordate at the base, tapered to a sharply pointed tip, the margins sharply and often relatively coarsely toothed, glabrous or sparsely roughened with minute, stiff hairs on the upper surface, sparsely to moderately pubescent with slightly longer hairs mostly along the veins on the undersurface, the secondary veins on the leaf undersurface usually easily observed, often irregularly fused toward their tips, the faint veinlets forming a dense, irregular network of relatively short areoles. Median and upper stem leaves relatively abruptly smaller toward the stem tip, with mostly long (the uppermost ones often short), unwinged to narrowly winged, nonclasping but somewhat sheathing petioles, the blades 1–7 cm long, mostly ovate (the uppermost narrowly ovate to narrowly lanceolate), cordate to short-tapered at the base, otherwise similar to the lower stem leaves. Inflorescences usually panicles with relatively long, loosely ascending, few- to many-headed, racemose branches, rarely reduced to a solitary terminal raceme or cluster, the heads appearing short- or long-stalked, the bracts along the ultimate branches 0.3–1.2 cm long, leaflike, linear or less commonly narrowly oblong-lanceolate, noticeably to only somewhat shorter and narrower than the adjacent foliage leaves. Heads mostly 1–2 cm in diameter (including the extended ray corollas) at flowering. Involucre 3.5–5.5 mm long, the bracts in 4–6 unequal, overlapping series. Involucral bracts linear to narrowly lanceolate or narrowly oblanceolate, angled to short-tapered at the bluntly to sharply pointed tip or with an abrupt, short, sharp point at the tip, the tip erect or ascending (the lowermost bracts occasionally slightly spreading), the slender midvein broadened in the apical 1/4–1/2 into a well-defined, diamond-shaped or elliptic (mostly 3–5 times as long as wide), green area (often also purplish-tinged along the margins), the outer surface glabrous or less commonly sparsely short-hairy, the margins irregularly hairy, especially toward the tip. Ray florets 8–15, usually in 1 series, the corollas well developed, 6–12 mm long, purplish blue to lavender. Disc florets 12–20, the corollas 3.5–5.0 mm long, the slender portion of the tube shorter than the slightly expanded apical portion, the lobes 0.6–0.9 mm long, 20–25 percent of the total length of the expanded portion. Pappus bristles 3–5 mm long, off-white to pale cream-colored or light tan, occasionally pale purplish-tinged. Fruits 1.5–2.5 mm long, mostly with 4 longitudinal ribs, purplish brown to brown, often with lighter ribs, glabrous or sparsely hairy. 2n=16, 32. August–November.

Scattered nearly throughout the state (eastern U.S. west to North Dakota and Oklahoma; Canada). Bottomland forests, mesic upland forests, banks of streams and rivers, and bases and ledges of bluffs; also railroads and roadsides.

A number of infraspecific taxa have been accepted within this species at various times. As noted in the treatment of S. urophyllum, Steyermark (1963) and many other botanists once considered that species as part of the variation within Aster sagittifolius until Almut G. Jones (1980) and Jones and Hiepko (1981) established that the type specimen of A. sagittifolius instead belongs to A. cordifolius. However, the attempts by Jones (1980, 1989) to recognize plants with less rhizome production and somewhat more truncate bases on the upper leaf blades seem ill-advised, given the variability of plants growing in different soils and with different light levels. Similarly, Steyermark (1963) and a few other authors segregated A. cordifolius var. polycephalus for this same morphological variant. On the other hand, Steyermark (1963) noted that some earlier authors had suggested that var. moratum (Shinners) G.L. Nesom (as A. cordifolius var. moratus (Shinners) Shinners) possibly represented hybrids between S. cordifolium and S. urophyllum (as A. sagittifolius), which seems reasonable. Steyermark (1963) also noted unpublished studies by Edgar Anderson suggesting that apparent widespread hybridization between S. cordifolium and S. drummondii (as Aster) was mostly the result of relatively recent, human-mediated habitat disturbances creating opportunities for them to grow in close proximity more frequently.