Senecio jacobaea |
Senecio triangularis |
|
---|---|---|
stinking willie, tansy ragwort |
arrow-leaf groundsel, arrow-leaf ragwort, arrowleaf butterweed, groundsel |
|
Habit | Perennials, 20–80(–100) cm (taprooted or branched caudices surmounting taproots). | Perennials, (20–)50–120(–200) cm (caudices branched, ± woody). |
Herbage | sparsely and unevenly tomentose, glabrescent except in leaf axils and among heads. |
glabrous or sparsely floccose-tomentose when young. |
Stems | (often purplish-tinged) usually single, sometimes loosely clustered. |
single or loosely clustered. |
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 narrowly triangular, (3–)4–10+ × 2–6 cm, bases usually ± truncate, sometimes tapered, margins usually dentate, rarely subentire (distal leaves subsessile, smaller). |
Ray florets | ± 13; corolla laminae 8–12 mm. |
± 8; corolla laminae 9–15 mm. |
Phyllaries | ± 13, 3–4(–5) mm, tips black or greenish. |
(± 8) ± 13 (± 21), 6–10 mm, tips usually green, rarely black. |
Calyculi | of 2–6 (inconspicuous) bractlets (less than 2 mm). |
of 2–6 bractlets (rarely more than 2 mm). |
Heads | (10–)20–60+ in corymbiform arrays. |
10–30(–60) in corymbiform to subracemiform arrays. |
Cypselae | all sparsely hairy or ray cypselae glabrous. |
glabrous. |
2n | = 40. |
= 40, 80. |
Senecio jacobaea |
Senecio triangularis |
|
Phenology | Flowering spring–early summer(–fall). | Flowering summer. |
Habitat | Disturbed sites, pastures, roadsides, and waste grounds | Damp places, open woodlands, especially rocky stream banks in coniferous forests |
Elevation | 0–1500 m (0–4900 ft) | 100–3300 m (300–10800 ft) |
Distribution |
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]
|
AK; AZ; CA; CO; ID; MT; NM; NV; OR; WA; WY; AB; BC; NT; YT; PH
|
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.) |
Plants of Senecio triangularis with narrow, subentire leaves that taper to the petioles are occasionally encountered in acid bogs in Oregon and Washington and less frequently elsewhere. They are regarded as edaphic variants; they have been recognized as var. angustifolius. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 20, p. 568. | FNA vol. 20, p. 566. |
Parent taxa | Asteraceae > tribe Senecioneae > Senecio | Asteraceae > tribe Senecioneae > Senecio |
Sibling taxa | ||
Synonyms | Jacobaea vulgaris | S. gibbonsii, S. saliens, S. triangularis var. angustifolius |
Name authority | Linnaeus: Sp. Pl. 2: 870. (1753) | Hooker: Fl. Bor.-Amer. 1: 332, plate 115. (1834) |
Web links |
|