7. Bidens frondosa L. (beggar-ticks, sticktight)
Pl. 274 a, b;
Map 1155
Plants annual,
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. August–October.
Scattered nearly
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.
This variable
species can be difficult to distinguish from B. vulgata.