Baccharis thesioides
Baccharis pilularis
Arizona baccharis, Mogollon baccharis
chaparral broom, coyote brush, dwarf chaparral false willow
erect to ascending, slender, striate-angled, glabrous, scarcely resinous.
spreading to ascending, dark brown, shiny, striate-angular, glabrous, often ± scurfy, usually resinous and sticky.
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).
present at flowering;
sessile or short-petiolate;
blades (1- or 3-nerved) oblanceolate to obovate, the smaller 5–40 × 2–15 mm (thick), bases cuneate, margins entire or coarsely dentate (teeth 3–9 distal to middles), faces glabrous, gland-dotted, resinous.
campanulate; staminate 3–6 mm, pistillate 3–6 mm.
hemispheric to campanulate; staminate 3.2–5 mm, pistillate 3–6 mm.
30;
corollas 2.2–3 mm.
19–43;
corollas 2.5–3.5 mm.
20–30;
corollas 3 mm.
20–34, 3–4 mm.
lanceolate, 1–5 mm, margins scarious, erose-ciliate, medians green, apices acute or obtuse (erose, abaxial faces glabrous).
ovate to lanceolate, 1–3 mm, margins yellowish, scarious, medians yellow proximally, green distally, apices obtuse to acute or acuminate (erose, abaxial faces papillose-scurfy).
(10–50+) in terminal, compact, rounded paniculiform arrays.
(100–200+) in (leafy) paniculiform arrays.
1.5–2.2 mm, 5-nerved, glabrous;
pappi 4–6 mm.
1–2 mm, 8–10-nerved, glabrous;
pappi 6–9 mm.
Baccharis thesioides
Baccharis pilularis
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies 2 (2 in the flora).
Baccharis pilularis can be distinguished by its dark brown stems, and serrate, obovate to oblanceolate leaves. In addition, plants from some dunes of the California coast are prostrate, a growth form unique to this genus in our region.
The common, weedy, widespread form is subsp. consanguinea, which is typically erect, with its larger leaves 15–40 mm. Subspecies pilularis is known only from exposed sandy dunes and bluffs along the central coast of California. Its growth habit is matlike, and its larger leaves are 5–15 mm. The prostrate habit of subsp. pilularis is strikingly different from the upright habit of subsp. consanguinea.
C. B. Wolf (1935) demonstrated that in at least some populations, the distinction between prostrate and erect forms has a genetic basis. Transplants from the wild of the prostrate and erect forms retained their respective growth habits when grown together in a sheltered location and the morphology of seedlings reflected the habit of the parents. Wolf’s arguments for recognizing the forms as subspecies are further supported by the existence of prostrate cultivars in the horticultural trade. On the other hand, both erect and prostrate forms grow in proximity throughout the range of subsp. pilularis. In many areas the forms intergrade completely; in others they can be easily distinguished. Two subspecies are recognized here, notwithstanding difficulties in identifying habit from pressed specimens, or by observations of populations where both growth forms coexist. Further study is needed, perhaps utilizing molecular characters and detailed observations of native populations.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Stems erect, rarely prostrate, brittle, forming erect or rounded shrubs; leaves mostly 15–40 mm; noncoastal and coastal California, Oregon | subsp. consanguinea |
1. Stems prostrate, flexible, forming mats; leaves mostly 5–15 mm; sandy, exposed habitats of coastal California | subsp. pilularis |
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