7. Bidens frondosa L. (beggar-ticks, sticktight)
Pl. 274 a, b;
terrestrial, usually with taproots. Stems 15–80(–120) cm, erect
or ascending, glabrous or inconspicuously pubescent with sparse, cobwebby
hairs, mostly at the nodes. Leaves all more or less similar, short- to more
commonly long-petiolate, opposite, the blade 3–12 cm long, broadly
ovate-triangular in outline, all except rarely those of the uppermost leaves 1
time ternately or pinnately divided or compound with 3–5 segments or
discrete leaflets, these lanceolate to narrowly ovate, angled or tapered at the
base, each with a well-developed stalk (this sometimes narrowly winged),
tapered to a sharply pointed tip, the margins usually sharply and finely to
coarsely toothed, sometimes minutely hairy, the surfaces glabrous or the
undersurface sparsely to moderately pubescent with minute, fine hairs.
Inflorescences of solitary terminal heads or appearing in loose, open clusters
or small panicles, the heads discoid or apparently discoid, rarely nodding at
fruiting. Involucre with the outer series of 5–8 bracts
5–25(–50) mm long, ascending to spreading, leaflike, linear to
narrowly oblong-oblanceolate or narrowly oblanceolate, the margins entire but
with short, spreading hairs, at least toward the base, the outer surface
glabrous or sparsely and minutely hairy, especially toward the base; the inner
series of 6–12 bracts 5–9 mm long, oblong to narrowly ovate or
ovate, glabrous. Chaffy bracts narrowly oblong to oblong-lanceolate, with
narrow to broad, yellowish margins but sometimes purplish-tinged at the tip.
Ray florets absent or 1–5, the corolla inconspicuous, 2–4 mm
long, yellow. Disc florets 20–100(–150), the corollas
2.5–4.0 mm long, yellow. Pappus of 2 awns 2–7 mm long, these
with downward-pointed barbs (upward-pointed elsewhere), erect to somewhat
spreading at fruiting. Fruits 5–12 mm long, wedge-shaped to
oblong-obovate, often slightly 3- or 4-angled (1 or both faces sometimes with a
broad, low longitudinal angle or ridge), the angles with minute, stiff, usually
ascending hairs, the faces dark brown to black, moderately to densely pubescent
with fine, more or less appressed hairs. 2n=24, 48, 72.
throughout the state (U.S. [including Alaska], Canada; introduced in Europe). Banks of streams and rivers, bottomland forests, margins of ponds, lakes, and
sinkhole ponds, swamps, sloughs, marshes, and fens; also ditches, fallow
fields, railroads, roadsides, and moist, open, disturbed areas.
species can be difficult to distinguish from B. vulgata.