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Plants of pond and stream shores, edges of marshes, wet meadows, sometimes spreading to adjacent drier sites.  Flowers late August to late September.  Native..

Annual.  Stems are often branching from near plant base.  Typical height is 2 to 3 feet.

Inflorescences consist of a few flower heads located at the summits of stems or at ends of branches in flat- or round-topped clusters.

Flower heads are typically discoid, or less often radiate with a few small, yellow rays (4+ mm long); erect (not nodding)Ray florets, when present, are neuterDisc florets are bisexual and fertile, the corollas yellow-orange, abruptly widened toward the summit; weakly attached to the cypselae and falling.   Involucral bracts are in two series: an inner series of short, yellowish, petal-like bracts, and an outer series of longer, narrower, green, leaf-like bracts.

Basal leaves are usually absent at flowering.    Stem leaves are opposite, lanceolate or oblanceolate, lacking petioles or gradually tapered to winged petioles; not divided into leaflets, coarsely toothed and/or irregularly lobed.

Cypselae are dark brown to black, compressed, weakly 4-angled,  flat or concave at the summit, narrowed toward the base, the faces often with minute tubercules.  The pappus is of 2-4 minutely barbed awns (1-4 mm long).

Similar species:  Bidens tripartita, B. frondosa, B. cernua.

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Note:  Some researchers consider B. connata and B. tripartita to be the same species.  Haines (2011) makes a convincing argument that both taxa should be recognized as different species, based on subtle differences in floral and fruit morphology; such as whether the disc corollas become abruptly widened or gradually widened apically; whether disc corollas are pale yellow or yellow-orange; whether faces of the cypselae are tuberculate or not; whether the disc corollas are persistent in fruit or not.  (As noted above.)  Also, B. tripartita tends to have larger heads with more disc florets per head (20-60 on avg.) compared with 20-40 on avg. for B. connata.

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