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Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

Key to Symphyotrichum, Key C: annual salt-marsh asters
[of subgenus Astropolium]

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1 Heads usually dense in an elongate, pyramidal-paniculate arrangement; inner phyllaries 6-7 mm long, phyllary apices linear-acuminate, distal margins often inrolled/involute, green zone of phyllaries narrowly lanceolate, usually extending the entire length of the phyllary, chartaceous bases short or absent; pappus accrescent, 4-5.5 mm long at maturity and usually longer than coiled ray corollas; [habitats wet, saline]
1 Heads corymbiform to thyrsiform, diffusely paniculate, or secund to subsecund and paniculiform arrangements or at the tips of long, bracteate branches; inner phyllaries 4-6.5 mm long, phyllary apices acute to acuminate, distal margins inrolled/involute or not, green zone of phyllaries lanceolate to elliptic, chartaceous bases usually conspicuous; pappus not accrescent, 3.5-4 (-5) mm long at maturity, longer or shorter than ray corollas; [habitats moist to wet, rarely saline].
..2 Phyllary tips appressed, acute, flat, inner phyllaries with broadly lanceolate, distinctly demarcated, apical green zone, proximal ½ -1/3 white-chartaceous; ray flower blades erect, often involute along the edges (curling inward lengthwise), rarely coiling back distally (if so, then only ca. 1/2 coil), usually shorter than mature pappus; disc flowers (3-) 7-14
..2 Phyllary tips loose, linear-acuminate, distal margins often inrolled/involute, inner phyllaries with narrowly lanceolate, often weakly demarcated apical green zone, white-chartaceous bases short, ca. 1/3-1/2 the length of the phyllaries; ray flower blades not involute along edges, usually coiling back distally in 1-4 or more coils, usually as long or longer than mature pappus; disc flowers either (6-) 8-15 or 11-23 or (20-) 33-45 (-50).
....3 Heads usually corymbiform to thyrsiform in arrangement (borne primarily on distal branches, distally clustered); inner phyllaries 4-5.5 (-6) mm long; phyllary apices acute to abruptly short-acuminate or long-acuminate, the distal margins inrolled/involute or not; ray flowers in 1 (-2) series, corollas 2-3 mm long, the blades 0.1-0.3 mm wide (dried), white to light pinkish or slightly blue, coiling back in 1-2 coils or less commonly remaining straight; disc flowers (6-) 8-15; [peninsular FL to s. AL]
....3 Heads diffusely paniculiform to pyramidal-paniculiform to corymbiform or second to subsecund and paniculiform; inner phyllaries 5-6.5 mm long; phyllary apices long-acuminate, the distal margins usually inrolled/involute; ray flowers in 1-3 series, corollas 2-7 mm long, the blades 0.2-0.8 mm wide (dried), white to blue or purple, coiling back in 2-5 coils; disc flowers either 11-23 or (20-) 33-45 (-50).
......4 Heads at first at ends of long, bracteate branches, then produced and maturing as axillary and nearly sessile or on very short lateral branches, commonly on one side of the main stem and appearing secund to subsecund, in paniculiform arrangements; ray flowers in 2-3 series, corollas mostly 2-3.5 (-4) mm long, the blades 0.2-0.4 mm wide (dry), blue to purple, coiling back in 2-3 (-4) coils; disc flowers 11-23; [e. GA s. to s. FL, w. to LA]
......4 Heads often at ends of long, bracteate branches, axillary heads usually maturing on elongate lateral branches, the whole arrangement often diffusely paniculiform to pyramidal-paniculiform, or heads more distally disposed and the arrangement corymbiform to thyrsiform; ray flowers in 1 series, corollas mostly 4-7 mm long, the blades 0.4-0.8 mm wide (dry), blue to white, coiling back in 3-5 coils; disc flowers (20-) 33-45 (-50); [sc. U.S. east to AL and scattered eastward as an introduction]
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