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mountain meadow butterweed, thick-leaf groundsel, thick-leaf ragwort

stinking willie, tansy ragwort

Habit Perennials, (15–)20–50(–70) cm (rhizomes branched, ± woody). Perennials, 20–80(–100) cm (taprooted or branched caudices surmounting taproots).
Herbage

glabrous.

sparsely and unevenly tomentose, glabrescent except in leaf axils and among heads.

Stems

1–(2–4).

(often purplish-tinged) usually single, sometimes loosely clustered.

Leaves

(thickish-turgid) progressively reduced distally; petiolate;

blades broadly lanceolate to subelliptic, 2.5–15 × 1–5 cm, bases tapered, margins sharply dentate to subentire (some teeth callous; mid leaves sometimes larger than proximal; distal leaves sessile, smaller, often clasping).

± evenly distributed (basal often withering before flowering); petiolate (sometimes obscurely);

blades ovate to broadly ovate (usually 1–3-pinnate, lobes mostly obovate to spatulate), (4–)7–20(–30) × (1–)2–5(–12) cm, bases usually tapered, ultimate margins dentate (distal leaves similar, smaller).

Ray florets

± 8 or ± 13;

corolla laminae 5–12 mm.

± 13;

corolla laminae 8–12 mm.

Phyllaries

(± 8) ± 13 or ± 21, 5–9 mm, tips black (villous).

± 13, 3–4(–5) mm, tips black or greenish.

Calyculi

of (1–)3–6 linear to filiform bractlets (lengths to 1/3 phyllaries).

of 2–6 (inconspicuous) bractlets (less than 2 mm).

Heads

(1–)4–12 in corymbiform arrays.

(10–)20–60+ in corymbiform arrays.

Cypselae

glabrous.

all sparsely hairy or ray cypselae glabrous.

2n

= 40.

= 40.

Senecio crassulus

Senecio jacobaea

Phenology Flowering summer. Flowering spring–early summer(–fall).
Habitat Moist to drying hillsides, meadows, other open places in forest associations Disturbed sites, pastures, roadsides, and waste grounds
Elevation 2200–3700 m (7200–12100 ft) 0–1500 m (0–4900 ft)
Distribution
from FNA
CO; ID; MT; NM; NV; OR; SD; UT; WY
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; IL; MA; ME; MI; MT; NJ; NY; OR; PA; WA; BC; NB; NF; NS; ON; PE; QC; SPM; Europe [Introduced in North America]
[WildflowerSearch map]
Discussion

Senecio jacobaea is a weed introduced from Europe and now well established in places of cool, damp summers. It is toxic to livestock and legally noxious in most states and provinces where it occurs.

The Russian botanist E. Wiebe (2000) resuscitated Jacobaea for plants that are treated here as Senecio jacobaea, S. erucifolius, and S. cannabifolius. Phylogenetic studies may confirm the utility of recognizing Jacobaea as a distinct genus; to do so here would be premature.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 20, p. 551. FNA vol. 20, p. 568.
Parent taxa Asteraceae > tribe Senecioneae > Senecio Asteraceae > tribe Senecioneae > Senecio
Sibling taxa
S. actinella, S. amplectens, S. ampullaceus, S. aphanactis, S. arizonicus, S. aronicoides, S. astephanus, S. atratus, S. bigelovii, S. blochmaniae, S. californicus, S. cannabifolius, S. clarkianus, S. elegans, S. elmeri, S. eremophilus, S. ertterae, S. erucifolius, S. flaccidus, S. fremontii, S. hydrophiloides, S. hydrophilus, S. integerrimus, S. jacobaea, S. lemmonii, S. lugens, S. lyonii, S. megacephalus, S. mohavensis, S. multidentatus, S. neowebsteri, S. parryi, S. pattersonensis, S. pseudoarnica, S. pudicus, S. quaylei, S. rapifolius, S. riddellii, S. sacramentanus, S. scorzonella, S. serra, S. sheldonensis, S. soldanella, S. spartioides, S. sphaerocephalus, S. spribillei, S. squalidus, S. sylvaticus, S. taraxacoides, S. triangularis, S. viscosus, S. vulgaris, S. warnockii, S. wootonii
S. actinella, S. amplectens, S. ampullaceus, S. aphanactis, S. arizonicus, S. aronicoides, S. astephanus, S. atratus, S. bigelovii, S. blochmaniae, S. californicus, S. cannabifolius, S. clarkianus, S. crassulus, S. elegans, S. elmeri, S. eremophilus, S. ertterae, S. erucifolius, S. flaccidus, S. fremontii, S. hydrophiloides, S. hydrophilus, S. integerrimus, S. lemmonii, S. lugens, S. lyonii, S. megacephalus, S. mohavensis, S. multidentatus, S. neowebsteri, S. parryi, S. pattersonensis, S. pseudoarnica, S. pudicus, S. quaylei, S. rapifolius, S. riddellii, S. sacramentanus, S. scorzonella, S. serra, S. sheldonensis, S. soldanella, S. spartioides, S. sphaerocephalus, S. spribillei, S. squalidus, S. sylvaticus, S. taraxacoides, S. triangularis, S. viscosus, S. vulgaris, S. warnockii, S. wootonii
Synonyms S. lapathifolius, S. semiamplexicaulis Jacobaea vulgaris
Name authority A. Gray: Proc. Amer. Acad. Arts 19: 54. (1883) Linnaeus: Sp. Pl. 2: 870. (1753)
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