Herbage usually glabrous or sparsely hispidulous, sometimes densely hirtellous, leaves sometimes stipitate-glandular, never resinous. Leaf blades oblanceolate to narrowly oblong-oblanceolate or nearly linear, mostly 10-40(-50) mm, margins usually entire (hispidulous-cilate, sometimes also on faces), sometimes shallowly toothed distally (especially along western margin of range; teeth in 1(-3) pairs). Involucres 3.2-5.5 × 2.5-4 mm. Phyllary apices yellowish, or if green, then margins scarious, not aristate, gland-dotted, without resin pockets. Florets (8-)11-17(-21); corollas 5-6 mm. Cypsela ribs not forming hornlike extensions. 2n = 12, 24.
Flowering (Apr-)Jul-Oct. Igneous or calcareous substrates, sometimes over gypsum, sandy or clay loam, commonly with Larrea-Prosopis; 400-1400(-1600) m; Ariz., N.Mex., Tex.; Mexico (Chihuahua, Coahuila).
Like other species of Isocoma, I. pluriflora usually is gland-dotted, but scattered plants are stipitate-glandular.
Common Name: southern goldenbush
Duration: Perennial
Nativity: Native
Lifeform: Subshrub
General: Weak shrub or large perennial herb, usually woody at least toward the base, 30-70 cm tall; stems erect to ascending, with hirtellous to subglabrous branchlets.
Leaves: Alternate along stems; blades linear to linear-oblanceolate, 1.5-5 mm wide and 2-4 cm long, the margins entire to sparsely short-dentate and hispidulous, surfaces densely punctate-resinous.
Flowers: Flower heads dicoid, yellow, numerous in dense terminal cymes; involucres cylindrical to turbinate, 4-5 mm high and 3-5 mm in diameter, the phyllaries overlapping in several graduated series, lanceolate to oblong, straw colored with yellowish or greenish tips; all florets discs, 7-15 per flower head, yellow.
Fruits: Achenes about 2 mm long, silky-strigose; topped with a pappus of straw-colored bristles about 4 mm long.
Ecology: Found in floodplains, flats, bajadas, seepy ground, ditches, and drainages, in sandy, gypseous or clay soils, from 3,000-6,500 ft (914-1981 m); flowers June-September.
Distribution: w TX to AZ; south to MEX
Notes: Here is another yellow-flowered Asteraceae shrub. It is quite common and widespread throughout New Mexico, especially the central, southern and eastern parts of the state, and found at the middle elevations in Arizona as well. It could be easily confused with its congener, Isocoma rusbyi. I rusbyi has larger flower heads, with involucres 6-10 mm high and 5-8 mm wide, and more florets, 19-25 per flower head (I. pluriflora's involucres are 4-5 mm high and 3-5 mm wide and there are 7-15 florets per head). I rusbyi is also less resinous than this species. I. pluriflora could also be mistaken for the common, widespread, and incredibly variable Ericameria nauseosa. The keys to that species are its densely tomentose stems and longer, narrower flower heads (involucres 6-16 mm long and only 2-4 mm wide). I. pluriflora is an invader of depleted rangeland and old fields.
Ethnobotany: Used as a lotion to heal infant's navel; a poultice was applied for muscular pain; leaves were chewed for coughs.
Etymology: Isocoma is from Greek iso- for equal and coma, hair of the head, referring to the flat-topped inflorences; pluriflora means many-flowered.
Synonyms: Haplopappus heterophyllus, H. pluriflorus, Isocoma wrightii, I. halophytica, Linosyris pluriflora
Editor: SBuckley 2010, AHazelton 2017
