The Jepson Herbarium
		University of California, Berkeley

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Annual to shrub, from taproot, rhizome, or button-like caudex.
Stem: 1–many, simple or branched.
Leaf: alternate; mostly basal to evenly distributed; proximal generally ± petioled; middle generally reduced, sessile, often clasping.
Inflorescence: heads radiate, disciform, or discoid, generally in cyme-like clusters; involucre cylindric to urn- or bell-shaped, main phyllaries generally 8, 13, or 21 in 1 series, subtended by few to many, generally much- reduced outer phyllaries, reflexed in fruit, green, often black-tipped, linear to narrowly lanceolate, glabrous or hairy; receptacle epaleate.
Ray flower: 0–21; ray generally yellow (white, pink-purple), occasionally much- reduced and scarcely exceeding phyllaries.
Disk flower: 3–100+; corolla tubular to bell-shaped, lobes erect to recurved, pale to deep yellow; anther tip ± triangular- ovate; style branch tips obtuse or truncate.
Fruit: cylindric, generally shallow-ribbed or -angled, glabrous or stiff-hairy; pappus of minutely barbed bristles, white to tan.
1000+ species: worldwide, especially abundant in warm temperate, subtrop and tropical areas at mid to upper elevations. (Latin: old man, from white pappus) [Barkley 2006 FNANM 20:544–570] Many North America species formerly treated as Senecio now in Packera. The common names groundsel, ragwort, and butterweed apply to species of both genera. Neither Pericallis hybrida B. Nord. [Senecio hybridus Regel, illeg.] nor Senecio squalidus L. <WEEDINESS SYMBOL 1> naturalized in CA; Senecio hieraciifolius L. var. hieraciifolius [Erechtites hieraciifolia (L.) DC. var. hieraciifolia (orth. var.)] not documented in CA.

Key to Senecio

1. Heads discoid, disciform, or minutely radiate, rays (if present) generally <= 2 mm, scarcely, if at all exceeding involucre

2. Heads disciform or minutely radiate, pistillate flowers present

3. Pistillate flowers fewer than disk flowers

4. Herbage densely curly-hairy; leaves 1–2-pinnately lobed or divided; disk flowers 40–50 ..... S. sylvaticus

4' Herbage glabrous or sparsely hairy; leaves generally dentate or 1-pinnately lobed; disk flowers 8–30

5. Cauline leaves generally narrowed at base, sometimes weakly clasping; involucre narrowly urn-shaped, finely hairy; CW, SCo, ChI ..... S. 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 ..... S. mohavensis (2)

3' Pistillate flowers more numerous than disk flowers

6. Lvs pinnately lobed ..... S. glomeratus

6' Lvs dentate or minutely dentate

7. Cauline leaves ± narrowly lanceolate, ± clasping, sharply and evenly fine-dentate, flat ..... S. minimus

7' Cauline leaves linear or lance-linear, tapered to base, remotely minutely dentate or appearing entire, margins ± rolled under ..... S. quadridentatus

2' Heads discoid, pistillate flowers 0

8. Annual

9. Herbage glabrous, glaucous ..... S. mohavensis (2)

9' Herbage glabrous or sparsely hairy when young, not glaucous ..... S. vulgaris

8' Biennial or perennial herb

10. Plant glabrous or minutely hairy among heads

11. Caudex erect; herbage ± red-tinged, not glaucous; petioles winged, leaves firm, not fleshy, dentate or minutely dentate; wet hillsides and meadows ..... S. hydrophiloides (2)

11' Caudex short, button-like; herbage blue-green, glaucous; petioles unwinged, leaves ± fleshy, entire to dentate; swamps and alkaline soils ..... S. hydrophilus (2)

10' Plant ± hairy, occasionally becoming ± glabrous in age

12. Fls 6–40 per head

13. Phyllaries (4)5–12 mm; disk flowers 35–45 ..... S. integerrimus var. exaltatus (2)

13' Phyllaries 3–5 mm; disk flowers 10–20 ..... S. scorzonella (2)

12' Fls 40–90+ per head

14. Phyllaries 8(13), 4–8 mm ..... S. aronicoides (2)

14' Phyllaries ± 21, 7–10 mm ..... S. astephanus

1' Heads radiate, rays 3–20 mm, generally well exceeding involucre

15. Shrub or subshrub with shrub-like branching; leaves or leaf segments narrowly linear to thread-like

16. Outer phyllaries prominent, often some > 1/2 inner ..... S. flaccidus

17. Herbage generally ± gray-tomentose ..... var. douglasii

17' Herbage generally ± glabrous ..... var. monoensis

16' Outer phyllaries inconspicuous or 0

18. Lvs 1–2-pinnately divided into linear, entire lobes ..... S. lyonii

18' Lvs generally entire or toothed (occasionally lobed in Senecio spartioides)

19. Phyllaries 3–5 mm ..... S. linearifolius var. linearifolius

19' Phyllaries 6–10 mm

20. Lf 0.5–3 mm wide; phyllaries generally 13; involucre generally 7–9 mm wide when pressed; fruit 3–5 mm; s CCo ..... S. blochmaniae

20' Lf 1–6 mm wide; phyllaries 8(13); involucre generally 3–6 mm wide when pressed; fruit 2–3.5 mm; SNH, SnBr, SNE, DMtns ..... S. spartioides

15' Annual or biennial to perennial herb; leaves or leaf segments of various shapes but generally wider than linear

21. Annual

22. Rays yellow ..... S. californicus

22' Rays red- or pink-purple ..... S. elegans

21' Biennial or per

23. Lvs deeply lobed or divided

24. Lvs sharply cut to pinnately lobed, lobes entire; phyllary tips green ..... S. clarkianus

24' Lvs 1–3-pinnately lobed, lobes obovate to spoon-shaped, ultimate margin dentate; phyllary tips generally black ..... S. jacobaea

23' Lvs entire or toothed

25. Rosette of basal leaves 0, leaves well distributed along stem

26. Plant generally 40–200 cm

27. Lvs ± linear to lanceolate, dentate to ± entire, tapered to ± sessile at base ..... S. serra var. serra

27' Lvs narrowly to widely triangular, dentate (rarely ± entire), at least proximal truncate to cordate at base ..... S. triangularis

26' Plant 2–30 cm

28. Plants <= 10 cm from branching rhizomes; stems 1–3; leaf entire, wavy or curled under; ray 5–10 mm ..... S. pattersonensis

28' Plants 10–30 cm from ± rhizomatous spreading bases; stems 2–several; leaf toothed to ± entire; ray 8–12 mm ..... S. fremontii

29. Distal leaves well developed; phyllaries 7–10 mm ..... var. fremontii

29' Distal leaves smaller, fewer; phyllaries 5–7 mm ..... var. occidentalis

25' Rosette of basal leaves present, leaves generally reduced distally on stem

30. Plant with stout rhizome ..... S. scorzonella (2)

30' Plant with short, erect, ± button-like caudex bearing many fleshy-fibrous roots

31. Plant generally glabrous or nearly so

32. Caudex erect; herbage ± red-tinged, not glaucous; petioles winged, leaves firm, not fleshy, dentate or minutely dentate; wet hillsides and meadows ..... S. hydrophiloides (2)

32' Caudex short, button-like; herbage blue-green, glaucous; petioles unwinged, leaves ± fleshy, entire to dentate; swamps, alkaline soils ..... S. hydrophilus (2)

31' Plant hairy when young, often ± glabrous in age

33. Lf sharply toothed, minutely dentate, or ± entire; phyllaries 8 (rarely 13); ray flowers 0 or 1–2 ..... S. aronicoides (2)

33' Lf entire to ± dentate; phyllaries 13 or 21; ray flowers 5, 8 or 13 ..... S. integerrimus

34. Ray flowers white; basal leaves distinctly petioled, blades ovate to rounded-deltate, or rarely obovate to oblanceolate ..... var. ochroleucus

34' Ray flowers yellow; basal leaves distinctly petioled or not, blades elliptic to lanceolate or oblanceolate, occasionally rounded-deltate to ± round

35. Plant densely or sparsely hairy; phyllaries lanceolate, tips black ..... var. exaltatus (2)

35' Plant distinctly and densely hairy; phyllaries linear to awl-like, tips generally green, rarely minutely black-tipped ..... var. major

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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