Shrubs, 100-200 cm (openly branched from bases). Stems erect to ascending, slender, striate-angled, glabrous, scarcely resinous. Leaves usually present at flowering; sessile; blades (1-nerved) linear-oblanceolate to narrowly oblong, 20-40(-80) × 4-8 mm, bases cuneate, margins evenly serrate (teeth spinulose, apices acute, faces finely gland-dotted, not resinous). Heads (10-50+ ) in terminal, compact, rounded paniculiform arrays. Involucres campanulate; staminate 3-6 mm, pistillate 3-6 mm. Phyllaries lanceolate, 1-5 mm, margins scarious, erose-ciliate, medians green, apices acute or obtuse (erose, abaxial faces glabrous). Staminate florets 20-30; corollas 3 mm. Pistillate florets 30; corollas 2.2-3 mm. Cypselae 1.5-2.2 mm, 5-nerved, glabrous; pappi 4-6 mm.

Flowering Aug-Nov. Mountains and canyons, oak-pine forests; 2200-2500 m; Ariz., N.Mex.; Mexico.

Baccharis thesioides is recognized by its erect stems, narrow, oblong, evenly serrate leaves with finely spinulose teeth, heads in relatively small rounded arrays, and 5-ribbed cypselae with short pappi. It is sometimes confused with B. bigelovii, which has broader and irregularly serrate leaves. The two taxa may belong to the same species complex centered in Mexico.

Common Name: Arizona baccharis

Duration: Perennial

Nativity: Native

Lifeform: Subshrub

General: Openly branched, slightly resinous shrub, 1-2 m tall; stems erect to ascending, slender, striate-angled.

Leaves: Alternate, sessile, and usually present while the plant is flowering; blades linear-lanceolate to narrowly oblong with a cuneate base, 2-4 cm long, 4-8 mm wide at the broadest point, which is usually above middle, the margins evenly serrate with fine spinulose teeth, and the surfaces finely gland-dotted but not resinous.

Flowers: Flower heads unisexual, discoid, arranged in terminal, compact, rounded panicles of 10-50 heads; involucre (the ring of bracts surrounding the flower head) campanulate, 3-6 mm, the bracts (phyllaries) lanceolate, 1-5 mm, graduated and imbricate in 4-6 series, green in the center with scarious margins; florets 2-3 mm, the corollas whitish (pistillate) to yellowish (staminate).

Fruits: Achenes 2 mm long, 5-nerved, glabrous, with a pappus of bristles, 4-6 mm.

Ecology: Found on rocky slopes, often in canyons, in the oak-pine belt from 4,000-8,000 ft (1219-2438 m); flowers August-November.

Distribution: AZ, NM; south to c MEX

Notes: Baccharis is a genus of shrubs with gland-dotted leaves; unisexual, discoid flower heads, with male and female flower heads on separate plants; and tufts of bristles (pappus) attached to the tops of the seed. B. thesioides is distinguished by its erect stems; narrow, oblong and evenly serrate leaves with finely spinulose teeth; flower heads in small rounded arrays; and 5-ribbed achenes. Can be confused with B. bigelovii but that species has broader and irregularly serrate leaves. B. thesioides has been described as a scaled-down version of B. salicifolia, at only about 1 m tall, with the flowers in smaller denser clusters, and narrower leaves with shaper, more distinct teeth on the margins.

Ethnobotany: Unknown, but other species in the genus have uses.

Etymology: Baccharis is named for Bacchus, the god of wine, while thesioides means like the genus Thesium.

Synonyms: None

Editor: SBuckley 2010, AHazelton 2015