Senecio triangularis
Senecio hydrophiloides
arrow-leaf groundsel, arrow-leaf ragwort, arrowleaf butterweed, groundsel
stout meadow groundsel, sweet marsh ragwort, sweet-marsh butterweed, tall groundsel
glabrous or sparsely floccose-tomentose when young.
usually glabrous or glabrescent (young plants sparsely tomentose).
single or loosely clustered.
usually single, sometimes 2–4 clustered (sometimes reddish-tinged).
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).
progressively reduced distally; usually petiolate (petioles often winged);
blades elliptic to broadly lanceolate, 5–15(–20) × 2–7 cm, bases broadly to narrowly tapered, margins dentate to denticulate (distal leaves sessile, bractlike).
± 8;
corolla laminae 9–15 mm.
0 or (± 3 or 5) ± 8;
corolla laminae 5–10 mm.
(± 8) ± 13 (± 21), 6–10 mm, tips usually green, rarely black.
(± 8) ± 13 (± 21), 4–9 mm, tips (minutely to prominently) black.
of 2–6 bractlets (rarely more than 2 mm).
of 2–5 bractlets (less than 2 mm).
10–30(–60) in corymbiform to subracemiform arrays.
(6–)15–30+ in congested or loose, corymbiform arrays.
glabrous.
glabrous.
= 40, 80.
= 40.
Senecio triangularis
Senecio hydrophiloides
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.)
Plants of Senecio hydrophiloides from toward the western end of the range tend to have the heads more or less congested and eradiate and stems loosely clustered; plants from toward the eastern edge tend to have heads loosely arrayed and radiate and stems single. The two forms have been recognized as weakly defined species (or varieties), the former as Senecio foetidus and the latter as S. hydrophiloides. They intergrade so completely that they are best treated as a single, variable taxon. The use of the epithet foetidus for the broadly conceived single species was based on a bibliographic misunderstanding; the correct epithet is hydrophiloides (T. M. Barkley 1978; A. Cronquist 1994).
In 1900, Thomas Howell gave the name Senecio oreganus to a collection from Lake Labish, near Salem, Oregon. The area has seen much disturbance and development since Howell’s time, and the plant appears to be extinct in the region. The collection is difficult to exclude from S. hydrophiloides, and the collection is here regarded as an odd outlier of S. hydrophiloides, which is known chiefly from east of the Cascade uplift. Howell’s collection and therefore the name S. oreganus also have been treated within S. sphaerocephalus (T. M. Barkley 1978; A. Cronquist 1955); that attribution appears to be in error. The “type” materials are now in the herbarium of Oregon State University in Corvallis.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
SW CO Wildflowers- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
PNW Herbaria, Turner Photog. 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
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