Burke: Senecio integerrimus vs. Senecio jacobaea

	Senecio integerrimus	Senecio jacobaea
	one-stemmed butterweed, western groundsel
Habit	Stout, fibrous-rooted perennial from a very short crown; stems solitary, 2-7 dm. tall; plants covered with white, loose hairs when young, but these missing in older plants except in the leaf axils.	Biennial or short-lived perennial from a taproot; stems solitary or several, erect, simple up to the inflorescence, 2-10 dm. tall.
Leaves	Usually entire, elliptic to broadly lanceolate, the basal ones petiolate, the blade and petiole 6-25 cm. long and 1-6 cm wide; cauline leaves progressively reduced upward, becoming sessile toward the top of the stem.	Evenly distributed along the stem, only slightly reduced upward, mostly 2-3 times pinnatifid, 4-20 cm. long and 2-6 cm. wide, the lower petiolate and often deciduous, the upper becoming sessile toward to top of the stem.
Flowers	Heads several to numerous in a rather congested inflorescence; involucre 5-10 mm. long; rays 6-15 mm. long, usually yellow, occasionally cream.	Heads rather numerous in a short, broad inflorescence, the disk usually 7-10 mm. wide; involucre about 4 mm. high, its bracts about 13, over 1 mm. wide, dark-tipped; rays about 13, 4-10 mm. long.

	Senecio integerrimus	Senecio jacobaea
Identification notes	A Senecio growing on dry ground, with a fairly tall, single, upright stem and large, entire leaves is probably this species, especially if the leaves are lightly covered with white, tangled hairs.	The upright stem covered with large, twice-divided leaves will usually identify this species; the 13 involucre bracts and 13 ray flowers can be helpful.
Flowering time	May-August	June-September
Habitat	Meadows and seasonally moist open areas from low elevations to the subalpine.	Roadsides, fields, pastures, forest edges, wastelots, and other disturbed areas.
Distribution	Occurring chiefly east of the Cascades crest in Washington, where widely distributed; British Columbia to California, east to the Great Plains and Great Lakes region. [WildflowerSearch map] [BONAP county map]	Occurring chiefly west of the Cascades crest in Washington; British Columbia to California, east to Idaho and Montana; also in northeastern North America. [WildflowerSearch map]
Origin	Native	Introduced from Eurasia
Conservation status	Not of concern	Not of concern
Sibling taxa	S. elmeri, S. fremontii, S. hydrophiloides, S. hydrophilus, S. lugens, S. neowebsteri, S. serra, S. sylvaticus, S. triangularis, S. viscosus, S. vulgaris	S. elmeri, S. fremontii, S. hydrophiloides, S. hydrophilus, S. integerrimus, S. lugens, S. neowebsteri, S. serra, S. sylvaticus, S. triangularis, S. viscosus, S. vulgaris
Subordinate taxa	S. integerrimus var. exaltatus, S. integerrimus var. ochroleucus
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 jacobaea

one-stemmed butterweed, western groundsel

Habit

Stout, fibrous-rooted perennial from a very short crown; stems solitary, 2-7 dm. tall; plants covered with white, loose hairs when young, but these missing in older plants except in the leaf axils.

Biennial or short-lived perennial from a taproot; stems solitary or several, erect, simple up to the inflorescence, 2-10 dm. tall.

Leaves

Usually entire, elliptic to broadly lanceolate, the basal ones petiolate, the blade and petiole 6-25 cm. long and 1-6 cm wide;

cauline leaves progressively reduced upward, becoming sessile toward the top of the stem.

Evenly distributed along the stem, only slightly reduced upward, mostly 2-3 times pinnatifid, 4-20 cm. long and 2-6 cm. wide, the lower petiolate and often deciduous, the upper becoming sessile toward to top of the stem.

Flowers

Heads several to numerous in a rather congested inflorescence;

involucre 5-10 mm. long;

rays 6-15 mm. long, usually yellow, occasionally cream.

Heads rather numerous in a short, broad inflorescence, the disk usually 7-10 mm. wide;

involucre about 4 mm. high, its bracts about 13, over 1 mm. wide, dark-tipped;

rays about 13, 4-10 mm. long.

Senecio integerrimus

Senecio jacobaea

Identification notes

A Senecio growing on dry ground, with a fairly tall, single, upright stem and large, entire leaves is probably this species, especially if the leaves are lightly covered with white, tangled hairs.

The upright stem covered with large, twice-divided leaves will usually identify this species; the 13 involucre bracts and 13 ray flowers can be helpful.

Flowering time

May-August

June-September

Habitat

Meadows and seasonally moist open areas from low elevations to the subalpine.

Roadsides, fields, pastures, forest edges, wastelots, and other disturbed areas.

Distribution

Occurring chiefly east of the Cascades crest in Washington, where widely distributed; British Columbia to California, east to the Great Plains and Great Lakes region.

[WildflowerSearch map]

[BONAP county map]

Occurring chiefly west of the Cascades crest in Washington; British Columbia to California, east to Idaho and Montana; also in northeastern North America.

[WildflowerSearch map]

Origin

Native

Introduced from Eurasia

Conservation status

Not of concern

Sibling taxa