5. Erigeron tenuis Torr. & A. Gray
Pl. 233 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, 36. April–June.
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
areas.
Most frequently,
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.