5. Erigeron tenuis Torr. & A. Gray
d–f; Map 975
Plants annual or
less commonly biennial, with shallow, fibrous roots. Stems 1 to few,
10–45 cm long, unbranched or sparsely 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, 2–5 cm long, mostly
long-petiolate, the blade oblanceolate to obovate or broadly obovate, 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, occasionally
3-lobed at the tip, the surfaces and margins sparsely to moderately (rarely
densely) pubescent with short, relatively stiff hairs (these often curved or
bent toward the base), occasionally the hairs longer and somewhat spreading
toward the stem base. Stem leaves few to occasionally relatively numerous,
1–5 cm long, the lower ones short-petiolate, the median and upper ones
sessile, the blade linear to oblanceolate or less commonly oblong-lanceolate,
angled or tapered to a bluntly or sharply pointed tip, short- to long-tapered,
angled, or narrowly rounded at the base, not or only slightly clasping the
stem, the margins entire or with few to several irregular teeth, often only
above the midpoint, the surfaces and margins sparsely to moderately hairy.
Inflorescences rounded to more or less flat-topped panicles, usually open and
with few to numerous heads. Involucre 2.5–4.0 mm long, the receptacle
4–10 mm in diameter at flowering, the bracts glabrous or more commonly
sparsely to moderately pubescent with short, appressed or curved hairs,
sometimes also minutely glandular. Ray florets 60–120, the corolla
3–5 mm long. Disc florets with the corolla 1.5–2.5 mm long.
Pappus of the ray and disc florets similar, both with an inner series of
10–15 threadlike bristles 1.2–2.2 mm long and an outer series
of few to several shorter bristles or slender scales 0.1–0.4 mm long.
Fruits 0.9–1.2 mm long, sparsely and inconspicuously hairy. 2n=18,
Scattered in the
southern half of the state (Kansas to Missouri south to Texas and Florida, possibly also North Carolina). Upland prairies, glades, tops of bluffs, and
margins of mesic upland forests; also pastures, roadsides, and open, disturbed
E. tenuis has the aspect of a small variant of E. strigosus.
However, a series of historical collections from Jasper County resemble E.
annuus more closely. These are more foliose plants, with relatively
well-developed leaves toward the stem tip, and with lower and median leaves
that have more teeth along the margins than is typical for the species in Missouri. Indeed, the inner bristles of the ray pappus constitute the only consistent
morphological distinction between E. tenuis and dwarf examples of the
other two species. Steyermark (1963) noted that the ray corollas of E.
tenuis are more often pinkish-tinged or bluish purple when fresh rather
than white. Erigeron tenuis has a much shorter overall flowering period
than do E. strigosus and E. annuus, and in any given year it
usually begins to flower a couple of weeks earlier than the other two species.