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common groundsel, old-man-in-the-spring

stinking willie, tansy ragwort

Habit Herbs annual, (1)2–5(6+) dm; caudices taprooted. Herbs perennial, 2–8(10) dm; caudices ± woody, branching, rhizomatous.
Stems

usually 1, rarely 2–3, glabrous or sparsely and unevenly tomentose.

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

Leaves

evenly distributed along stems, oblanceolate to narrowly obovate or ovate, bases tapering;

margins lobulate to dentate, ultimate margins secondarily denticulate;

proximal petiolate;

distal sessile.

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

loose corymb-like arrays;

bracts few, inconspicuous.

compound corymb-like arrays;

bracts conspicuous but small.

Involucres

urceolate.

widely cylindric or urn-shaped.

Ray florets

0.

~13;

rays 8–12 mm.

Disc florets

(30)55–65.

60–70+.

Phyllaries

21, 4–6 mm;

tips usually black.

13, 3–4(5);

tips black or dark green.

Calyculi

2–4(6+) bractlets, 2–3 mm.

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

Fruits

2–2.5 mm, sparsely to densely pubescent, rarely glabrous.

0.75–1.3 mm, sparsely hairy or glabrous.

Heads

8–20.

(10)20–60+.

2n

=40.

=40.

Senecio vulgaris

Senecio jacobaea

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

Disturbed areas. Flowering Feb–Oct. 0–1000 m. CR, ECas, Est, Lava, Sisk, WV. CA, ID, NV, WA; throughout North America; Asia, Europe. Exotic.

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 342
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. integerrimus, S. jacobaea, S. serra, S. sphaerocephalus, S. sylvaticus, S. triangularis, S. viscosus
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
Synonyms Jacobaea vulgaris
Web links