Baccharis sarothroides |
Baccharis pilularis |
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broom baccharis, desert broom, greasewood, groundsel, rosin-brush |
chaparral broom, coyote brush, dwarf chaparral false willow |
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Habit | Shrubs, 100–400 cm (much branched, broomlike). | Shrubs, 15–450 cm (prostrate and mat-forming to erect and rounded, much branched). | ||||
Stems | erect, striate, sharply angled, green distally, glabrous, resinous. |
spreading to ascending, dark brown, shiny, striate-angular, glabrous, often ± scurfy, usually resinous and sticky. |
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Leaves | cauline (proximal withered and/or sparse at flowering); sessile; blades (1-nerved) linear-lanceolate, 5–15 × 1–2 mm, reduced to scales distally, thick, bases narrowed, margins entire (often revolute), apices acute, faces glabrous, minutely gland-dotted, 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. |
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Involucres | cylindric to hemispheric; staminate 4–5.2 mm, pistillate 3–8 mm. |
hemispheric to campanulate; staminate 3.2–5 mm, pistillate 3–6 mm. |
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Pistillate florets | 19–31; corollas 2.5–3.5 mm. |
19–43; corollas 2.5–3.5 mm. |
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Staminate florets | 18–35; corollas 4.2–5 mm. |
20–34, 3–4 mm. |
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Phyllaries | ovate to lanceolate, 1–5 mm, margins yellowish, slightly scarious, medians green to yellow, apices rounded to acute (greenish, abaxial faces glabrous, resinous). |
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). |
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Heads | borne singly (on nearly leafless branches) or (laterally on branchlets) in dense paniculiform arrays. |
(100–200+) in (leafy) paniculiform arrays. |
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Cypselae | 2–2.6 mm, finely 8–10-nerved, glabrous; pappi 7–12 mm. |
1–2 mm, 8–10-nerved, glabrous; pappi 6–9 mm. |
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2n | = 18. |
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Baccharis sarothroides |
Baccharis pilularis |
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Phenology | Flowering Aug–Nov. | |||||
Habitat | Gravelly and sandy washes, roadsides, railroads, mesquite flats, chaparral | |||||
Elevation | 50–1500 m (200–4900 ft) | |||||
Distribution |
AZ; CA; NM; TX; Mexico (Baja California, Baja California Sur, Sinaloa, Sonora)
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CA; NM; OR; nw Mexico
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Discussion | Baccharis sarothroides is recognized by its broomlike habit, narrow, sharply angular, nearly leafless, green stems, soon-withering proximal leaves, scalelike distal leaves, and heads often terminal on long branches. Specimens from California have smaller heads that sometimes are arranged laterally along the stems. (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.) |
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Key |
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Source | FNA vol. 20, p. 33. | FNA vol. 20, p. 29. | ||||
Parent taxa | ||||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | A. Gray: Proc. Amer. Acad. Arts 17: 211. (1882) | de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 407. (1836) | ||||
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