1 Plant aquatic, the leaves finely divided into segment < 0.5 mm wide; pappus awn 13-25 (-40) mm long |
1 Plant terrestrial or wetland, but not aquatic, the leaf segment > 0.5 mm wide; pappus awn lacking or present, if present < 10 mm long. |
2 Inner cypsela more-or-less equally 4-angled, thickest near the middle and equally tapered to both ends; ray floret white, pink, or pale yellowish (or absent). |
3 Leaves 2-3× dissected, primary lobe > 20, the ultimate segment rounded to acute, 2-10 mm wide; ray floret pale yellowish |
3 Leaves mostly once- pinnate, primary lobe 3-7, the ultimate segment serrate and acute, 8-50 mm wide; ray floret white or absent. |
4 Ray floret 5-8, the ligule 5-16 mm long; cypsela 2-awned, the awn 1-2 mm long; outer phyllaries (8-) 12 (-16) |
4 Ray floret 0 (or if a few present, the ligule < 3 mm long); cypsela 3 (-5)-awned, the awn 1-3 mm long; outer phyllaries 7-10 |
2 Inner cypsela flattened (if 4-angled, the alternating angles acute and obtuse), thickest toward the tip; ray floret yellow or orange (or absent). |
5 Most leaves simple, the margin dentate to serrate or incised (with 3-7 lobe). |
6 Leaves (except sometimes the lower) sessile; heads usually nodding, at least in age. |
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7 Ray present, (10-) 15-25 (-30) mm long; pales (receptacular bract) with orange or red tips; outer cypsela 6-8 mm, inner cypsela 8-10 mm ( margin not notably thickened or winged); pappus of 2-4 awn 3-5 mm long |
6 Leaves with a distinct petiole 1-4 cm long (this sometimes winged); heads erect. |
8 Ray 12-25+ mm long; cypsela 2.5-4.5 mm long, the margin not barbed or ciliate |
8 Ray absent or 2-5 (-12) mm long; cypsela (3-) 6-13 mm long, the margin sometimes barbed or ciliate. |
9 Involucre usually campanulate to cylindric, sometimes ± hemispheric; disc floret (6-) 10-25 (-60); cypsela faces usually ± striate, sometimes tuberculate; [MD northward, estuarine]. |
10 Cypsela usually antrorsely strigillose throughout; cypsela angles weak or absent |
10 Cypsela glabrous or sparsely setulose; cypsela angles strong to weak or rarely absent Bidens eatonii |
9 Involucre campanulate to hemispheric or broader; disc floret (5-) 20-60 (-150+); cypsela faces usually smooth or tuberculate (not notably striate); [collectively widely distributed, in a diversity of wetland types]. |
11 Cypsela ± flattened, sometimes weakly 3 (-4)-angled and 3 (-4)-awned, the faces usually smooth, seldom notably tuberculate; disc corolla 4- lobed, light yellow; anther usually pale |
11 Cypsela (at least inner) usually ± 4-angled and 4-awned, the faces usually strigose or tuberculate; disc corolla 5- lobed, orange-yellow; anther usually blackish |
5 Most leaves either 1- pinnately compound, the 3-5 (-7) leaflet petiolulate, or -1-2× pinnately lobed. |
12 Ray floret 0, or ray 1-3, the laminae 2-3.5 mm long. |
13 Calyculus bractlet (2-) 4 (-5), seldom ciliate; disc floret usually 10-20 |
13 Calyculus bractlet (5-) 8-16 (-21), usually ciliate; disc floret 20-150. |
14 Calyculus bractlet (5-) 8 (-10); leaves usually 3 (-5)-foliolate |
14 Calyculus bractlet 10-16 (-21); leaves usually laciniate or pinnatisect |
12 Ray floret (5-) 8-13, the laminae 10-30 mm long. |
15 Cypsela 2.5-4× as long as wide |
15 Cypsela 1.5-2 (-2.5)× as long as wide. |
16 Cypsela 2.5-5 mm long, the margin not winged, barbed, or ciliate |
16 Cypsela (4-) 5-8 mm long, the margin usually barbed or ciliate, and often also corky- winged. |
17 Calyculus bractlet 8-12 (-16), these (4-) 5-7 (-12) mm long; calyculus bractlet glabrous or fine- pubescent on the lower surface; achene 2.5-5 mm long |
17 Calyculus bractlet 12-21, these (6-) 8-12 (20) mm long; calyculus bractlet usually coarsely short- pubescent on the lower surface; achene 5-7 mm long |