4. Erigeron strigosus Muhl. ex Willd. var. strigosus (daisy fleabane, whitetop fleabane)

E. annuus ssp. strigosus (Muhl. ex Willd.) Wagenitz

E. strigosus var. beyrichii (Fisch. & C.A. Mey.) Torr. & A. Gray

E. strigosus var. discoideus J.W. Robbins ex A. Gray

E. ramosus Britton, Sterns & Poggenb.

Pl. 233 i, j; Map 974

Plants annual or less commonly biennial, with shallow, fibrous roots. Stems 1 to several, 30–70(–90) cm long, often well branched above the lower 1/3, sparsely to moderately pubescent (occasionally roughened) with appressed to ascending hairs (some of the longer hairs sometimes spreading toward the tip). Basal leaves sometimes withered by flowering time, 3–15 cm long, mostly long-petiolate, the blade oblanceolate to elliptic-oblanceolate, mostly long-tapered at the base, mostly bluntly to sharply pointed at the tip, the margins entire or coarsely and sharply toothed usually above the midpoint, the surfaces and margins sparsely to moderately pubescent with short, relatively stiff hairs (these often curved or bent toward the base). Stem leaves usually appearing relatively few (this mostly because the leaves are sparser toward the stem tip), 1–10 cm long, the lower ones short-petiolate, the median and upper ones sessile, the blade linear to oblanceolate, angled or tapered to a mostly sharply pointed tip, short- to long-tapered at the base, not clasping the stem, the margins entire or with few irregular teeth toward the tip, the surfaces and margins sparsely to moderately hairy. Inflorescences rounded to more or less flat-topped panicles, usually open, often with numerous heads. Involucre 2–5 mm long, the receptacle 4–12 mm in diameter at flowering, the bracts glabrous or more commonly sparsely pubescent with short, appressed and/or longer, more or less spreading hairs, often also minutely glandular. Ray florets 50–100 or rarely absent, the corolla 4–7 mm long. Disc florets with the corolla 1.5–2.5 mm long. Pappus of the ray florets (when present) and disc florets of 2 types, an inner series of 8–15 threadlike bristles 1.2–2.2 mm long and an outer series of several shorter bristles or slender scales 0.1–0.4 mm long, the ray florets lacking the longer, inner series. Fruits 0.8–1.2 mm long, sparsely and inconspicuously hairy. 2n=18, 27, 36, 54. May–September.

Common throughout the state (U.S., Canada; introduced in Europe). Banks of streams and rivers, openings of mesic to dry upland forests, savannas, upland prairies, and glades; also pastures, old fields, railroads, roadsides, and open, disturbed areas.

This species exists throughout much of its range as an apomictic polyploid, with sexual diploids apparently uncommon in portions of the southeastern United States (Noyes, 2000b). Cronquist (1947c) treated E. strigosus as comprising four varieties. Of these, small-headed plants (var. beyrichii) and rayless plants (var. discoideus) are rare mutations that occur sporadically within populations (including in Missouri) and probably should be accorded no higher taxonomic rank than that of a form. At the other extreme, two perennial, rhizomatous varieties endemic to dolomite glades in central Alabama, var. calcicola J. Allison and var. dolomiticola J. Allison, were described relatively recently (Allison and Stevens, 2001) and are so distinctive that they perhaps should be considered varieties of a novel species. The var. septentrionalis (Fernald & Wiegand) Fernald refers to plants growing mostly to the north of Missouri that have relatively broad basal leaves and long hairs on the stem, with the pubescence of the involucre unusual in appearing flattened and narrowly ribbonlike when dried. It should be searched for in northern Missouri. As noted above, Frey et al. (2003) considered this variant to be more closely related to E. annuus than to E. strigosus.

Erigeron strigosus can be difficult to distinguish from the closely related E. annuus. Both species are widespread in Missouri, but E. strigosus tends to occupy somewhat drier sites and tends not to occur in cropped areas. The fewer narrower leaves give the plants a sparser, more open appearance. The largest leaves of plants of E. strigosus tend to be narrower and less toothed along the margins. Morphologically intermediate plants are encountered sporadically but fairly frequently.

Native Americans used this species medicinally for heart ailments and as an analgesic (Moerman, 1998).