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stinking willie, tansy ragwort

stout meadow groundsel, sweet marsh butterweed

Habit Herbs perennial, 2–8(10) dm; caudices ± woody, branching, rhizomatous. Herbs perennial or biennial, 3–10(14) dm; caudices erect, button-like, with fleshy, fibrous, unbranched roots.
Stems

1, or rarely 2–4 and loosely clustered, often purple-tinged, sparsely and unevenly tomentose.

1, sometimes 2–4 and clustered, sometimes reddish tinged, glabrous or glabrate; young plants sometimes sparsely hairy.

Leaves

basal usually withering before flowering;

cauline ± evenly distributed along stems;

distal slightly smaller; ovate to broadly ovate, bases tapered, usually 1–3-pinnate, ultimate margins dentate;

lobes obovate to spatulate, petiolate.

mostly basal;

cauline reduced distally, elliptic to broad lanceolate; firm, bases tapering;

margins dentate to denticulate;

surfaces glabrous;

petioles often distinctly winged;

distal sessile and bract-like.

Inflorescences

compound corymb-like arrays;

bracts conspicuous but small.

loose or congested corymb-like arrays;

bracts 0 or inconspicuous.

Involucres

widely cylindric or urn-shaped.

widely cylindric to campanulate.

Ray florets

~13;

rays 8–12 mm.

0 or 3–8;

rays 5–10 mm.

Disc florets

60–70+.

30–45.

Phyllaries

13, 3–4(5);

tips black or dark green.

8, 13 or 21, 4–9 mm;

tips black.

Calyculi

2–6 bractlets, inconspicuous, usually < 2 mm.

2–5 bractlets, inconspicuous; < 2 mm.

Fruits

0.75–1.3 mm, sparsely hairy or glabrous.

2–3 mm, glabrous.

Heads

(10)20–60+.

(6)15–30+.

2n

=40.

=40.

Senecio jacobaea

Senecio hydrophiloides

Distribution
[WildflowerSearch map]
[WildflowerSearch map]
[BONAP county map]
Discussion

Disturbed areas, pastures, roadsides. Flowering May–Sep. 0–1600 m. Casc, CR, Est, Sisk, WV. CA, ID, WA; north to British Columbia, northeast to MT, northeastern North America; Europe. Exotic.

Senecio jacobea is an introduced weed, originally from Europe. It establishes in places with cool, wet summers and is particularly toxic to livestock. In most states where it occurs, this species has been declared a noxious weed.

Damp hillsides, meadows, seeps. Flowering Jun–Jul. 1000–1900 m. BR, BW, ECas, Lava, Sisk, WV. CA, ID, NV, WA; north to British Columbia, northeast to Alberta, east to WY, southeast to UT. Native.

Plants in the western part of this species’ range tend to have single stems, more congested inflorescences, and more ray florets and have been treated by some authors as a distinct species (S. foetidus). Those further east have more stems, a looser inflorescence, and fewer ray florets. T.M. Barkley (1978) noted that these two forms intergrade so completely that they should be treated as a single species.

Source Flora of Oregon, volume 2, page 340
Debra Trock
Flora of Oregon, volume 2, page 339
Debra Trock
Sibling taxa
S. aronicoides, S. crassulus, S. ertterae, S. fremontii, S. hydrophiloides, S. hydrophilus, S. integerrimus, S. serra, S. sphaerocephalus, S. sylvaticus, S. triangularis, S. viscosus, S. vulgaris
S. aronicoides, S. crassulus, S. ertterae, S. fremontii, S. hydrophilus, S. integerrimus, S. jacobaea, S. serra, S. sphaerocephalus, S. sylvaticus, S. triangularis, S. viscosus, S. vulgaris
Synonyms Jacobaea vulgaris Senecio foetidus, Senecio foetidus var. foetidus, Senecio foetidus var. hydrophiloides, Senecio oreganus
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