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stinking willie, tansy ragwort

lambstongue ragwort, western groundsel

Habit Herbs perennial, 2–8(10) dm; caudices ± woody, branching, rhizomatous. Herbs perennial or biennial, (1)2–7 dm; caudices button-like, with fleshy, fibrous, unbranched roots.
Stems

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

1, loosely arachnoid-tomentose, or villous, glabrate with age.

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 progressively reduced distally; ± petiolate;

basal and lower cauline elliptic, lanceolate, linear, oblanceolate, rounded-deltate, rarely suborbiculate, bases tapered or truncate to cordate;

margins entire or dentate;

distal becoming sessile and bract-like.

Inflorescences

compound corymb-like arrays;

bracts conspicuous but small.

corymb-like arrays;

bracts 0 or inconspicuous.

Involucres

widely cylindric or urn-shaped.

urn-shaped.

Ray florets

~13;

rays 8–12 mm.

5, rarely 0;

rays 6–15(20) mm, yellow or white to pale yellow.

Disc florets

60–70+.

35–45.

Phyllaries

13, 3–4(5);

tips black or dark green.

(8)13 or 21;

tips usually black, sometimes green.

Calyculi

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

1–5+, inconspicuous, usually < 2 mm.

Fruits

0.75–1.3 mm, sparsely hairy or glabrous.

2.5–3 mm, usually glabrous, sometimes hairy along ribs.

Heads

(10)20–60+.

6–15(30+).

2n

=40.

=40, 80.

Senecio jacobaea

Senecio integerrimus

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.

Western North America. 5 varieties; 3 varieties treated in Flora.

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. hydrophiloides, S. hydrophilus, S. jacobaea, S. serra, S. sphaerocephalus, S. sylvaticus, S. triangularis, S. viscosus, S. vulgaris
Subordinate taxa
S. integerrimus var. exaltatus, S. integerrimus var. major, S. integerrimus var. ochroleucus
Synonyms Jacobaea vulgaris
Web links