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Key to SenecioView taxon page for Senecio
(For a list of species in Senecio, use the above link.) Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots. 1. Heads discoid, disciform, or minutely radiate, rays (if present) generally <= 2 mm, scarcely, if at all exceeding involucre  Group of bracts more or less held together as a unit, subtending a flower, fruit (acorn cup), or inflorescence. 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  Having margins with sharp, relatively coarse teeth pointing outward, not tipward. or 1-pinnately lobed; disk flowers 8–30 5. Cauline leaves generally narrowed at base, sometimes weakly clasping; involucre narrowly urn-shaped  Widening more or less abruptly at the base and then gradually or abruptly narrowed toward the tip. , finely hairy; CW, SCo, ChI ..... S. aphanactis 5' Mid and distal cauline leaves widest at base, truncate  Abruptly (not gradually) narrower or smaller at base or tip, as if cut straight across or nearly so. to cordate-clasping – 1–2+ cm wide – at base, often ± purple tinged; involucre cylindric  Elongate, with parallel sides and, at any point, round in transverse section. or urn-shaped, glabrous; D ..... S. mohavensis (2) 3' Pistillate flowers more numerous than disk flowers 6' Leaves dentate or minutely dentate 7. Cauline leaves ± narrowly lanceolate  Narrowly elongate, widest in the basal half, often tapered to an acute tip. , ± clasping, sharply and evenly fine-dentate, flat ..... S. minimus 7' Cauline leaves linear  Elongate, with nearly parallel sides; narrower than elliptic or oblong. or lance-linear, tapered  Gradually (not abruptly) narrower or smaller at base or tip. to base, remotely minutely dentate or appearing entire  Having margins that are continuous and smooth (i.e., without teeth, lobes, etc.). , margins ± rolled under ..... S. quadridentatus 2' Heads discoid, pistillate flowers 0 8' Biennial or perennial  Completing life cycle (germination through death) in more than two years or growing seasons, generally non-woody (at least above ground) to woody; includes perennial herbs as well as subshrubs to trees; the abbreviation 'per' only refers to perennial herb, not to the word 'perennial' alone. herb 10. Plant glabrous or minutely hairy among heads 11. Caudex erect  Upright; vertically oriented. ; herbage ± red-tinged, not glaucous; petioles  Leaf stalk, connecting leaf blade to stem; sometimes more or less indistinct. 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. Flowers 6–40 per head  1. A dense, often spheric inflorescence of sessile or subsessile flowers. 2. In Asteraceae and some other groups, a head-like inflorescence is one in which sessile or subsessile inflorescence units (e.g., heads in Asteraceae, umbels enclosed by involucres in Eriogonum), instead of individual flowers, are attached in a short dense cluster without an evident axis or branches. 12' Flowers 40–90+ per head 1' Heads radiate, rays 3–20 mm, generally well exceeding involucre 15. Shrub or subshrub with shrub-like branching; leaves or leaf  Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets). segments narrowly linear to thread-like 16' Outer phyllaries inconspicuous or 0 18. Leaves 1–2-pinnately divided into linear, entire lobes  1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth. ..... S. lyonii 18' Leaves generally entire or toothed (occasionally lobed in Senecio spartioides) 20. Leaf 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' 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 ..... S. spartioides 15' Annual or biennial to perennial herb; leaves or leaf segments of various shapes but generally wider than linear 21' Biennial or perennial herb 23. Leaves deeply lobed or divided 24' Leaves 1–3-pinnately lobed, lobes obovate to spoon-shaped, ultimate margin dentate; phyllary tips generally black ..... S. jacobaea 23' Leaves entire or toothed 25. Rosette of basal  At or near the base of a plant or plant part. Especially said of leaves clustered near the ground or of a placenta confined to the base of an ovary. leaves 0, leaves well distributed along stem 26. Plant generally 40–200 cm 27. Leaves ± linear to lanceolate, dentate to ± entire, tapered to ± sessile  Without a petiole, peduncle, pedicel, or other kind of stalk. at base ..... S. serra var. serra 27' Leaves narrowly to widely triangular, dentate (rarely ± entire), at least proximal truncate to cordate  Heart-shaped; often pertaining to a leaf in which the blade base on both sides of the petiole is rounded and convex. at base ..... S. triangularis 28' Plants 10–30 cm from ± rhizomatous spreading  Oriented more or less perpendicularly to the axis of attachment; often, more or less horizontal. bases; stems 2–several; leaf toothed to ± entire; ray 8–12 mm ..... S. fremontii 25' Rosette of basal leaves present, leaves generally reduced distally on stem 30. Plant with stout rhizome  1. In seed plants, stem that is often elongate, more or less horizontal, usually underground; distinguished from roots by bearing of leaves, leaf scars, axillary buds, etc. 2. In ferns, stem that is located underground, embedded in leaf litter, on rocks or in rock crevices, or on trees or tree branches, often scaly or hairy; distinguished from roots by bearing of fronds (roots rarely bear fronds), and their greater diameter. ..... S. scorzonella (2) 30' Plant with short, erect, ± button-like caudex  Generally short, sometimes woody, more or less vertical stem of a perennial, at or beneath ground level. 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. Leaf sharply toothed, minutely dentate, or ± entire; phyllaries 8 (rarely 13); ray flowers 0 or 1–2 ..... S. aronicoides (2) 34. Ray flowers white; basal leaves distinctly petioled, blades ovate  Egg-shaped (i.e., widest below the middle) in two dimensions (i.e., in one plane), as a leaf. to rounded-deltate, or rarely obovate to oblanceolate ..... var. ochroleucus 34' Ray flowers yellow; basal leaves distinctly petioled or not, blades elliptic  In the shape of a flattened circle or ellipse; wider than linear to lanceolate or oblanceolate, occasionally rounded-deltate to ± round 35' Plant distinctly and densely hairy; phyllaries linear to awl-like, tips generally green, rarely minutely black-tipped ..... var. major
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