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lambstongue ragwort, western groundsel

stinking willie, tansy ragwort

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

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

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

Leaves

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.

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.

Inflorescences

corymb-like arrays;

bracts 0 or inconspicuous.

compound corymb-like arrays;

bracts conspicuous but small.

Involucres

urn-shaped.

widely cylindric or urn-shaped.

Ray florets

5, rarely 0;

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

~13;

rays 8–12 mm.

Disc florets

35–45.

60–70+.

Phyllaries

(8)13 or 21;

tips usually black, sometimes green.

13, 3–4(5);

tips black or dark green.

Calyculi

1–5+, inconspicuous, usually < 2 mm.

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

Fruits

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

0.75–1.3 mm, sparsely hairy or glabrous.

Heads

6–15(30+).

(10)20–60+.

2n

=40, 80.

=40.

Senecio integerrimus

Senecio jacobaea

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

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

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.

Source Flora of Oregon, volume 2, page 339
Debra Trock
Flora of Oregon, volume 2, page 340
Debra Trock
Sibling taxa
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
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
Subordinate taxa
S. integerrimus var. exaltatus, S. integerrimus var. major, S. integerrimus var. ochroleucus
Synonyms Jacobaea vulgaris
Web links