1	"Heads discoid, disciform, or minutely radiate, rays (if present) generally <= 2 mm, scarcely, if at all exceeding involucre"	2
1	"Heads radiate, rays 3--20 mm, generally well exceeding involucre"	15
2	"Heads disciform or minutely radiate, pistillate flowers present"	3
2	"Heads discoid, pistillate flowers 0"	8
3	"Pistillate flowers fewer than disk flowers"	4
3	"Pistillate flowers more numerous than disk flowers"	6
4	"Herbage densely curly-hairy; leaves 1--2-pinnately lobed or divided; disk flowers 40--50"	"Senecio sylvaticus"
4	"Herbage glabrous or sparsely hairy; leaves generally dentate or 1-pinnately lobed; disk flowers 8--30"	5
5	"Cauline leaves generally narrowed at base, sometimes weakly clasping; involucre narrowly urn-shaped, finely hairy; CW, SCo, ChI"	"Senecio aphanactis"
5	"Mid and distal cauline leaves widest at base, truncate to cordate-clasping --- 1--2+ cm wide --- at base, often +- purple tinged; involucre cylindric or urn-shaped, glabrous; D"	"Senecio mohavensis"
6	"Leaves pinnately lobed"	"Senecio glomeratus"
6	"Leaves dentate or minutely dentate"	7
7	"Cauline leaves +- narrowly lanceolate, +- clasping, sharply and evenly fine-dentate, flat"	"Senecio minimus"
7	"Cauline leaves linear or lance-linear, tapered to base, remotely minutely dentate or appearing entire, margins +- rolled under"	"Senecio quadridentatus"
8	Annual	9
8	"Biennial or per"	10
9	"Herbage glabrous, glaucous"	"Senecio mohavensis"
9	"Herbage glabrous or sparsely hairy when young, not glaucous"	"Senecio vulgaris"
10	"Plant glabrous or minutely hairy among heads"	11
10	"Plant +- hairy, occasionally becoming +- glabrous in age"	12
11	"Caudex erect; herbage +- red-tinged, not glaucous; petioles winged, leaves firm, not fleshy, dentate or minutely dentate; wet hillsides and meadows"	"Senecio hydrophiloides"
11	"Caudex short, button-like; herbage blue-green, glaucous; petioles unwinged, leaves +- fleshy, entire to dentate; swamps and alkaline soils"	"Senecio hydrophilus"
12	"Flowers 6--40 per head"	13
12	"Flowers 40--90+ per head"	14
13	"Phyllaries (4)5--12 mm; disk flowers 35--45"	"Senecio integerrimus var. exaltatus"
13	"Phyllaries 3--5 mm; disk flowers 10--20"	"Senecio scorzonella"
14	"Phyllaries 8(13), 4--8 mm"	"Senecio aronicoides"
14	"Phyllaries +- 21, 7--10 mm"	"Senecio astephanus"
15	"Shrub or subshrub with shrub-like branching; leaves or leaf segments narrowly linear to thread-like"	16
15	"Annual or biennial to perennial herb; leaves or leaf segments of various shapes but generally wider than linear"	21
16	"Outer phyllaries prominent, often some > 1/2 inner"	17
16	"Outer phyllaries inconspicuous or 0"	18
17	"Herbage generally +- gray-tomentose"	"Senecio flaccidus var. douglasii"
17	"Herbage generally +- glabrous"	"Senecio flaccidus var. monoensis"
18	"Leaves 1--2-pinnately divided into linear, entire lobes"	"Senecio lyonii"
18	"Leaves generally entire or toothed (occasionally lobed in <i>Senecio spartioides</i>)"	19
19	"Phyllaries 3--5 mm"	"Senecio linearifolius var. linearifolius"
19	"Phyllaries 6--10 mm"	20
20	"Leaf 0.5--3 mm wide; phyllaries generally 13; involucre generally 7--9 mm wide when pressed; fruit 3--5 mm; s CCo"	"Senecio blochmaniae"
20	"Leaf 1--6 mm wide; phyllaries 8(13); involucre generally 3--6 mm wide when pressed; fruit 2--3.5 mm; SNH, SnBr, SNE, DMtns"	"Senecio spartioides"
21	Annual	22
21	"Biennial or per"	23
22	"Rays yellow"	"Senecio californicus"
22	"Rays red- or pink-purple"	"Senecio elegans"
23	"Leaves deeply lobed or divided"	24
23	"Leaves entire or toothed"	25
24	"Leaves sharply cut to pinnately lobed, lobes entire; phyllary tips green"	"Senecio clarkianus"
24	"Leaves 1--3-pinnately lobed, lobes obovate to spoon-shaped, ultimate margin dentate; phyllary tips generally black"	"Senecio jacobaea"
25	"Rosette of basal leaves 0, leaves well distributed along stem"	26
25	"Rosette of basal leaves present, leaves generally reduced distally on stem"	30
26	"Plant generally 40--200 cm"	27
26	"Plant 2--30 cm"	28
27	"Leaves +- linear to lanceolate, dentate to +- entire, tapered to +- sessile at base"	"Senecio serra var. serra"
27	"Leaves narrowly to widely triangular, dentate (rarely +- entire), at least proximal truncate to cordate at base"	"Senecio triangularis"
28	"Plants <= 10 cm from branching rhizomes; stems 1--3; leaf entire, wavy or curled under; ray 5--10 mm"	"Senecio pattersonensis"
28	"Plants 10--30 cm from +- rhizomatous spreading bases; stems 2--several; leaf toothed to +- entire; ray 8--12 mm"	29
29	"Distal leaves well developed; phyllaries 7--10 mm"	"Senecio fremontii var. fremontii"
29	"Distal leaves smaller, fewer; phyllaries 5--7 mm"	"Senecio fremontii var. occidentalis"
30	"Plant with stout rhizome"	"Senecio scorzonella"
30	"Plant with short, erect, +- button-like caudex bearing many fleshy-fibrous roots"	31
31	"Plant generally glabrous or nearly so"	32
31	"Plant hairy when young, often +- glabrous in age"	33
32	"Caudex erect; herbage +- red-tinged, not glaucous; petioles winged, leaves firm, not fleshy, dentate or minutely dentate; wet hillsides and meadows"	"Senecio hydrophiloides"
32	"Caudex short, button-like; herbage blue-green, glaucous; petioles unwinged, leaves +- fleshy, entire to dentate; swamps, alkaline soils"	"Senecio hydrophilus"
33	"Leaf sharply toothed, minutely dentate, or +- entire; phyllaries 8 (rarely 13); ray flowers 0 or 1--2"	"Senecio aronicoides"
33	"Leaf entire to +- dentate; phyllaries 13 or 21; ray flowers 5, 8 or 13"	34
34	"Ray flowers white; basal leaves distinctly petioled, blades ovate to rounded-deltate, or rarely obovate to oblanceolate"	"Senecio integerrimus var. ochroleucus"
34	"Ray flowers yellow; basal leaves distinctly petioled or not, blades elliptic to lanceolate or oblanceolate, occasionally rounded-deltate to +- round"	35
35	"Plant densely or sparsely hairy; phyllaries lanceolate, tips black"	"Senecio integerrimus var. exaltatus"
35	"Plant distinctly and densely hairy; phyllaries linear to awl-like, tips generally green, rarely minutely black-tipped"	"Senecio integerrimus var. major"