Aquatic and Wetland Vascular Plants of the Northern Great Plains
49. Asteraceae, the Aster Family
3. Bidens L. -- Beggarticks1. Bidens bipinnata L. -- Spanish needles
Erect, branching annual 3-12(17) dm tall, glabrous or seldom hispidulous. Leaves pinnate-pinnatifid to bipinnate, 4-20 cm long including the petiole which is 2-5 cm long, the leaflets ovate to oblong and deeply lobed, lobes acute to nearly rounded. Heads inconspicuously radiate, appearing discoid, 4-6 mm across; outer involucral bracts 7-10, linear, acute, shorter than the inner ones; rays yellowish-white and dark striate, less than 5 mm long, not exceeding the disk florets. Achenes with (2)3-4 retrorsely barbed, yellowish awns, the body brown to blackish, linear, mostly 10-18 mm long and much surpassing the involucre or the outermost achenes shorter. Aug--Oct. Moist to wet disturbed areas and shores; uncommon in e NE, probably as a sporadic introduction from farther s; (MA to NE s to FL, TX, AZ and into Mex.; also S.Amer. and intro. in the Old World).
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