Flora of North America species comparison

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Senecio jacobaea

Senecio sylvaticus

stinking willie, tansy ragwort

heath groundsel, wood groundsel, woodland groundsel, woodland ragwort
Habit Perennials, 20–80(–100) cm (taprooted or branched caudices surmounting taproots). Annuals, (15–)30–80+ cm (taproots fibrous-rooted).
Herbage

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

puberulent (hairs abundant, curly).
Stems

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

single.
Leaves

± 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).

evenly distributed; petiolate;

blades obovate to oblong, 3–7(–12) × 1–3(–4) cm, usually 1–2-pinnate, bases tapered, ultimate margins dentate (distal leaves similar, clasping, bractlike).
Ray florets

± 13;

corolla laminae 8–12 mm.

0 or 1–8+;

corolla laminae usually 1–2+ mm (barely surpassing phyllaries).
Phyllaries

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

± 13 (± 21), 4–7+ mm, tips greenish or minutely black.
Calyculi

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

0 or of 1–5+ linear to filiform bractlets.
Heads

(10–)20–60+ in corymbiform arrays.

12–24 in corymbiform arrays.
Cypselae

all sparsely hairy or ray cypselae glabrous.

hairy (especially on angles).
2n

= 40.

= 40.

Senecio jacobaea

Senecio sylvaticus
Phenology Flowering spring–early summer(–fall). Flowering late spring–summer (northern areas of cool, climate); winter (southern areas).
Habitat Disturbed sites, pastures, roadsides, and waste grounds Mildly disturbed woodlands, open, sandy sites
Elevation 0–1500 m (0–4900 ft) 100–300 m (300–1000 ft)
Distribution
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]
from FNA
CA; LA; MA; MI; NJ; OH; OR; PA; WA; WI; BC; NB; NF; NS; PE; QC; Eurasia [Introduced in North America]
[WildflowerSearch map]
[BONAP county 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.)

Senecio sylvaticus is a Eurasian weed that favors cool, wet climates. It is well established in coastal areas of the Pacific Coast and in parts of Newfoundland and Quebec; elsewhere in the flora, it appears to be sporadic.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 20, p. 568. FNA vol. 20, p. 563.
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. 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
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. 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. taraxacoides, S. triangularis, S. viscosus, S. vulgaris, S. warnockii, S. wootonii
Synonyms Jacobaea vulgaris
Name authority Linnaeus: Sp. Pl. 2: 870. (1753) Linnaeus: Sp. Pl. 2: 868. (1753)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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