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stinking willie, tansy ragwort

arrowleaf groundsel

Habit Herbs perennial, 2–8(10) dm; caudices ± woody, branching, rhizomatous. Herbs perennial, (2)5–12(20) dm; caudices branching, woody, rhizomatous.
Stems

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

1 or 2–4 and loosely clustered, glabrous or sparsely pubescent.

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.

basal present at flowering;

cauline ± evenly distributed along stems, gradually reduced distally, narrowly to widely triangular, bases tapered to truncate or cordate;

margins dentate, rarely subentire;

surfaces sparsely tomentose to nearly glabrous;

proximal petiolate;

distal sessile.

Inflorescences

compound corymb-like arrays;

bracts conspicuous but small.

corymb- or ± raceme-like arrays;

bracts conspicuous.

Involucres

widely cylindric or urn-shaped.

cylindric to narrowly campanulate.

Ray florets

~13;

rays 8–12 mm.

~8;

rays 9–15 mm.

Disc florets

60–70+.

35–45.

Phyllaries

13, 3–4(5);

tips black or dark green.

(8)13(21), 6–10 mm;

tips green, rarely black.

Calyculi

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

2–6 bractlets, inconspicuous, rarely > 2 mm.

Fruits

0.75–1.3 mm, sparsely hairy or glabrous.

2.5–3.5 mm, glabrous.

Heads

(10)20–60+.

10–30(60).

2n

=40.

=40, 80.

Senecio jacobaea

Senecio triangularis

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.

Open areas, rocky streambanks, wet meadows, bogs, damp places in coniferous forests. Flowering May–Sep. 0–2800 m. BR, BW, Casc, CR, ECas, Est, Lava, Sisk, WV. CA, ID, NV, WA; north to AK, northeast to MT, east to WY, southeast to NM. Native.

Some plants with narrow, subentire leaves that taper to the petioles have been found in acidic bogs in Washington and Oregon. A few authors recognize these as variety angustifolia. However, this author has observed several specimens (specifically indicated as being collected in bogs) that had both narrower leaves and the wider leaves more typical of variety triangularis on the same plant.

Source Flora of Oregon, volume 2, page 340
Debra Trock
Flora of Oregon, volume 2, page 341
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. integerrimus, S. jacobaea, S. serra, S. sphaerocephalus, S. sylvaticus, S. viscosus, S. vulgaris
Synonyms Jacobaea vulgaris Senecio gibbonsii, Senecio triangularis var. angustifolius, Senecio triangularis var. triangularis
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