Aquatic and Wetland Vascular Plants of the Northern Great Plains
49. Asteraceae, the Aster Family
3. Bidens L. -- Beggarticks6. Bidens frondosa L.
Erect annual 1.5-8 dm tall, usually branched; stems rather slender, often purplish, glabrous except slightly villous at upper nodes. Leaves all or mostly ternate, some larger ones sometimes pinnately divided into 5 leaflets, the leaflets ovate to lanceolate, glabrous to puberulent above, sparingly pubescent beneath, acuminate, serrate, the terminal leaflet largest, 3-9 cm long, 1-3.5 cm wide; petioles 1-4 cm long. Heads discoid, campanulate to hemispheric, 1-2 cm across; outer involucral bracts 5-10, typically 8, often sparingly ciliate, usually surpassing the disk. Achenes with 2 retrorsely barbed awns, the body dark brown to blackish, 4-9 mm long, antrorsely appressed-hairy. Late Jul--Oct. Same habitats as B. cernua; common, often abundant; (Newf. and N.S. to WA, s to GA, LA and CA).
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