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.

Santa Catalina Mountains
Oracle Ridge Trail
7/30/15

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