OregonFlora: Senecio triangularis vs. Senecio hydrophiloides

	Senecio triangularis	Senecio hydrophiloides
	arrowleaf groundsel	stout meadow groundsel, sweet marsh butterweed
Habit	Herbs perennial, (2)5–12(20) dm; caudices branching, woody, rhizomatous.	Herbs perennial or biennial, 3–10(14) dm; caudices erect, button-like, with fleshy, fibrous, unbranched roots.
Stems	1 or 2–4 and loosely clustered, glabrous or sparsely pubescent.	1, sometimes 2–4 and clustered, sometimes reddish tinged, glabrous or glabrate; young plants sometimes sparsely hairy.
Leaves	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.	mostly basal; cauline reduced distally, elliptic to broad lanceolate; firm, bases tapering; margins dentate to denticulate; surfaces glabrous; petioles often distinctly winged; distal sessile and bract-like.
Inflorescences	corymb- or ± raceme-like arrays; bracts conspicuous.	loose or congested corymb-like arrays; bracts 0 or inconspicuous.
Involucres	cylindric to narrowly campanulate.	widely cylindric to campanulate.
Ray florets	~8; rays 9–15 mm.	0 or 3–8; rays 5–10 mm.
Disc florets	35–45.	30–45.
Phyllaries	(8)13(21), 6–10 mm; tips green, rarely black.	8, 13 or 21, 4–9 mm; tips black.
Calyculi	2–6 bractlets, inconspicuous, rarely > 2 mm.	2–5 bractlets, inconspicuous; < 2 mm.
Fruits	2.5–3.5 mm, glabrous.	2–3 mm, glabrous.
Heads	10–30(60).	(6)15–30+.
2n	=40, 80.	=40.

	Senecio triangularis	Senecio hydrophiloides
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion	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.	Damp hillsides, meadows, seeps. Flowering Jun–Jul. 1000–1900 m. BR, BW, ECas, Lava, Sisk, WV. CA, ID, NV, WA; north to British Columbia, northeast to Alberta, east to WY, southeast to UT. Native. Plants in the western part of this species’ range tend to have single stems, more congested inflorescences, and more ray florets and have been treated by some authors as a distinct species (S. foetidus). Those further east have more stems, a looser inflorescence, and fewer ray florets. T.M. Barkley (1978) noted that these two forms intergrade so completely that they should be treated as a single species.
Source	Flora of Oregon, volume 2, page 341 Debra Trock	Flora of Oregon, volume 2, page 339 Debra Trock
Sibling taxa	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	S. aronicoides, S. crassulus, S. ertterae, S. fremontii, S. hydrophilus, S. integerrimus, S. jacobaea, S. serra, S. sphaerocephalus, S. sylvaticus, S. triangularis, S. viscosus, S. vulgaris
Synonyms	Senecio gibbonsii, Senecio triangularis var. angustifolius, Senecio triangularis var. triangularis	Senecio foetidus, Senecio foetidus var. foetidus, Senecio foetidus var. hydrophiloides, Senecio oreganus
Web links	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 SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	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 SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Senecio hydrophiloides

arrowleaf groundsel

stout meadow groundsel, sweet marsh butterweed

Habit

Herbs perennial, (2)5–12(20) dm; caudices branching, woody, rhizomatous.

Herbs perennial or biennial, 3–10(14) dm; caudices erect, button-like, with fleshy, fibrous, unbranched roots.

Stems

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

1, sometimes 2–4 and clustered, sometimes reddish tinged, glabrous or glabrate; young plants sometimes sparsely hairy.

Leaves

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.

mostly basal;

cauline reduced distally, elliptic to broad lanceolate; firm, bases tapering;

margins dentate to denticulate;

surfaces glabrous;

petioles often distinctly winged;

distal sessile and bract-like.

Inflorescences

corymb- or ± raceme-like arrays;

bracts conspicuous.

loose or congested corymb-like arrays;

bracts 0 or inconspicuous.

Involucres

cylindric to narrowly campanulate.

widely cylindric to campanulate.

Ray florets

~8;

rays 9–15 mm.

0 or 3–8;

rays 5–10 mm.

Disc florets

35–45.

30–45.

Phyllaries

(8)13(21), 6–10 mm;

tips green, rarely black.

8, 13 or 21, 4–9 mm;

tips black.

Calyculi

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

2–5 bractlets, inconspicuous; < 2 mm.

Fruits

2.5–3.5 mm, glabrous.

2–3 mm, glabrous.

Heads

10–30(60).

(6)15–30+.

=40, 80.

=40.

Senecio hydrophiloides

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

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.

Damp hillsides, meadows, seeps. Flowering Jun–Jul. 1000–1900 m. BR, BW, ECas, Lava, Sisk, WV. CA, ID, NV, WA; north to British Columbia, northeast to Alberta, east to WY, southeast to UT. Native.

Plants in the western part of this species’ range tend to have single stems, more congested inflorescences, and more ray florets and have been treated by some authors as a distinct species (S. foetidus). Those further east have more stems, a looser inflorescence, and fewer ray florets. T.M. Barkley (1978) noted that these two forms intergrade so completely that they should be treated as a single species.

Source

Flora of Oregon, volume 2, page 341
Debra Trock

Flora of Oregon, volume 2, page 339
Debra Trock

Sibling taxa