Bidens

Scientific name

Bidens L.

Common names

water-marigold, beggarticks, stickseeds, tickseeds, tickseed sunflowers, devil's sticktight, bur-marigolds

Family

Asteraceae

Native distribution

cosmopolitan; mainly subtropical, tropical, and warm-temperate New World

Species cultivated

Bidens beckii Torr. ex Spreng. [syn: Megalodonta beckii (Torr. ex Spreng.) Greene.] is rarely cultivated, but may be found in specialty stores or for trade with hobbyists

these amphibious to wetland species are offered as garden ornamentals

Bidens aristosa (Michx.) Britton

B. cernua L.

B. connata Muhl. ex Willd.

B. coronata (L.) Britton [synonym of Bidens trichosperma (Michx.) Britton]

B. frondosa L.

B. laevis (L.) "Britton, Sterns & Poggenb."

B. polylepis S.F.Blake

Adventive distribution

cosmopolitan

Weed status

can be weedy

Habit

amphibious to emergent, sometimes floating, helophytic herbs

Brief description

Annual or perennial. Stem ascending to erect, often striate. Leaves opposite decussate, sessile or petiolate; leaf blade simple, lobed, or compound; margins entire to serrate when emersed (submerged leaves appearing whorled and finely dissected in B. beckii). Inflorescence a terminal head, solitary or in cymes, pedunculate, heads usually radiate; involucre hemispheric; phyllaries biseriate. Ray florets absent or few, usually sterile, ligulate, yellow or white; disk florets bisexual, fertile, tube 5-lobed, yellow to orange.

Natural habitat

moist habitats, wetlands, still or slow-moving shallow water; lakes, ponds, rivers, and streams

Additional comments

Bidens contains approximately 250 species, most of which are in wetland habitats and tolerate periods of submersion. Bidens beckii (=Megalodonta beckii) is the only truly aquatic species.