3. Heterotheca subaxillaris (Lam.) Britton & Rusby (camphorweed, telegraph plant)

H. latifolia Buckley

H. subaxillaris ssp. latifolia (Buckley) Semple

H. latifolia var. arkansana B. Wagenkn.

Pl. 236 f–h; Map 988

Plants annual or biennial, with taproots. Stems 15–150(–200) cm long, usually relatively stout, sparsely to more commonly moderately to densely pubescent with relatively long, spreading hairs mostly with expanded, bulbous, pustular bases, also with moderate to dense, minute, sessile or slightly stalked glands. Stem leaves 1–9 cm long, lanceolate to elliptic or ovate, some of the lower leaves sometimes narrowed somewhat above the base and expanded again below the midpoint, mostly shallowly cordate at the clasping base (the lowermost leaves occasionally tapered to a short petiole and with a separate pair of auricles clasping the stem), angled or short-tapered to a bluntly or more commonly sharply pointed tip, the margins mostly sharply toothed, those of the upper leaves sometimes only irregularly wavy or entire, also hairy, the surfaces appearing green or slightly grayish-tinged, moderately roughened with loosely appressed to somewhat curved hairs, these all or mostly with an expanded, bulbous base, also with sparse to dense, minute, sessile to slightly stalked glands. Involucre 5–10 mm long, the bracts in 4–6 unequal, overlapping series, narrowly lanceolate to nearly linear, the green central stripe usually easily observed, not hidden by the sparse to moderate, short, curved hairs, these mostly along the midvein, moderately glandular. Ray florets 15–40, the corollas 5–10 mm long. Disc florets 25–60, the corollas 3–9 mm long, glabrous. Pappus of the ray florets absent, that of the disc florets consisting of an outer series of several bristlelike scales 0.2–0.6 mm long and an inner series of 25–45 bristles 4–9 mm long. Fruits 2–4 mm long, obscurely 3- or 4-nerved, those of the ray florets 3- or 4-angled, glabrous, those of the disc florets somewhat flattened, the surface moderately hairy. 2n=18. July–November.

Scattered, mostly in the Mississippi Lowlands Division and in counties bordering the Missouri and Mississippi Rivers (nearly throughout the U.S. except some northwestern states; Mexico). Sand prairies and loess hill prairies; also fallow fields, margins of crop fields, banks of ditches, railroads, roadsides, and open, disturbed areas, especially in sandy soil.

Some botanists have accepted three species in this complex: true H. subaxillaris of the southeastern Coastal Plain, the widespread H. latifolia, and the southwestern H. psammophila B. Wagenkn. (Wagenknecht, 1960; Steyermark, 1963; Semple, 1996). Other studies have tended to emphasize the overall similarities and innate variability of these plants in various habitats and soil types (Burk, 1961; Harms, 1965b; Nesom, 1990e; Semple, 2004), and a single-species classification without any additional varieties or subspecies is accepted here.