Baccharis salicifolia |
Baccharis |
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mule's fat, mule-fat, seepwillow, water wally |
baccharis, false willow, groundsel-tree |
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Habit | Shrubs, 30–400 cm (stems clustered). | Perennials, subshrubs, shrubs, or trees, 10–600 cm (dioecious [rarely monoecious], usually glabrous, often resinous; bases woody, rarely rhizomatous). | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Stems | spreading to ascending, green to tan, simple proximally, sparingly branched distally, striate-angled, glabrous or minutely hairy, resinous and ± resin-varnished. |
(1–20+) usually erect or ascending, rarely prostrate (usually striate-angled, rarely terete and smooth; usually green), glabrous, glabrate, hispidulous, or villous, often resinous. |
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Leaves | present at flowering (abundant, well developed); sessile or petiolate; blades lanceolate-elliptic, slightly falcate (willowlike), 30–150 × 3–20 mm, bases attenuate, margins usually finely serrate from bases to apices, sometimes entire, apices acute to acuminate, faces glabrous, gland-dotted, ± resinous. |
cauline (sometimes withering and sparse or absent at flowering); alternate; sessile or petiolate; blades 1- or 3-nerved, linear, lanceolate, ovate, oblong, obovate, or rhombic (usually reduced distally), margins entire or coarsely serrate, faces usually glabrous, rarely hispidulous or villous, often gland-dotted and resinous. |
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Involucres | hemispheric; staminate 3–6 mm, pistillate involucres 3–6 mm. |
cylindric to campanulate or hemispheric, 3–9 mm diam. |
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Receptacles | flat, tholiform, or conic, pitted or smooth (glabrous, tomentose, or glandular), usually epaleate. |
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Pistillate florets | 50–150; corollas 2–3.5 mm. |
20–150; corollas whitish, filiform-tubular, lobes 5, spreading-reflexed, ± deltate to lance-ovate; style branches (glabrate, flattened), appendages lacking. |
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Staminate florets | (10–)17–48; corollas 4–6 mm. |
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Phyllaries | ovate to lanceolate, 2–4 mm, margins scarious, erose or irregularly dentate, midribs distinct, medians green or reddish, apices (greenish or brownish purple) obtuse to acuminate (pale and dry, glabrous). |
20–40 in 2–5 series (mid usually green, sometimes red or purple), 1-nerved, ovate to lanceolate, unequal, margins usually scarious, often erose or ciliate, sometimes keeled (midribs evident or not, apices obtuse to acute or acuminate, sometimes keeled), usually glabrous, rarely hispid. |
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Heads | in terminal, compound corymbiform arrays (often involving distal branches). |
(sessile or pedicellate, unisexual) discoid, usually in paniculiform or corymbiform, sometimes racemiform arrays or borne singly. |
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Cypselae | 0.8–1.5 mm, 5-nerved, glabrous; pappi 3–6 mm. |
light brown, obovoid to cylindric, ± compressed, 5–10-nerved, glabrous or hispid; pappi persistent or falling, of 25–50 whitish to tawny, rarely brownish (elongating and usually surpassing phyllaries in fruit), minutely barbellate, apically attenuate bristles in 1–3 series. |
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Functionally | staminate florets 10–50; corollas white to pale yellow, tubes about equal to narrowly funnelform throats, lobes 5, spreading-reflexed, deltate to lance-ovate (pappi of 20–40 equal, often crisped and minutely barbellate or distally plumose bristles). |
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x | = 9. |
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2n | = 18, 36. |
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Baccharis salicifolia |
Baccharis |
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Phenology | Flowering (Jan–)Mar–Oct. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Stream banks, dry washes, sandy flood plains, riparian woodlands, disturbed sites, ditches | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Elevation | 30–2400 m (100–7900 ft) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Distribution |
AZ; CA; CO; NM; NV; TX; UT; Mexico; South America
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Mostly New World tropics and warm-temperate regions; especially diverse in South America |
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Discussion | Baccharis salicifolia is part of a complex that extends through the southwestern United States, Mexico, Central America, and South America to Argentina and Chile (J. Cuatrecasas 1968). It is recognized by the narrowly lanceolate, willowlike, finely serrate leaves with acute or acuminate apices, smallish heads in dense clusters, reddish phyllaries, and 5-nerved cypselae. By tagging and measuring individual plants throughout the year, D. H. Wilken (1972) demonstrated that B. salicifolia has distinct seasonal forms. The North American plants were once known as B. glutinosa or B. viminea, which were differentiated from each other by differences in woodiness, leaf size and serration, and flowering time. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Species 350–450 (21 in the flora). Baccharis comprises mostly dioecious shrubs with gland-dotted leaves and is sister to the polygamo-dioecious genera Archibaccharis and Heterothalamus. Sections have been delimited within Baccharis (e.g., D. A. Giuliano 2001; Giuliano and G. L. Nesom 2003; Nesom 1990h, 1998). Species of Baccharis often occur in wet sites such as stream banks, washes, ditches, and marshes. Useful taxonomic characters include habit, branching structure, leaf shape, size, margins, and vestiture, arrangement of heads, and number of nerves on cypselae. Collectors should try to collect both staminate and pistillate individuals to facilitate identification. Hybridization and introgression have been found between Baccharis halimifolia and B. neglecta, and between B. halimifolia and B. angustifolia. Intermediates between B. thesioides and B. bigelovii have been collected in southern Arizona. Baccharis is of little economic importance, except for species that are invasive or toxic to livestock (P. E. Boldt 1989). Baccharis is not generally palatable to cattle; it could become the only forage available as a result of overgrazing. In the southwestern United States, B. pteronioides is a hazard to cattle; B. halimifolia, B. angustifolia, and B. glomeruliflora cause similar problems in the eastern United States (G. E. Burrows and R. J. Tyrl 2001). Baccharis pilularis invades overgrazed or eroded rangelands in California and Oregon. Baccharis halimifolia has been introduced in Australia, infesting large areas along the eastern coast, prompting the search for biological control agents (Boldt). Neomolina F. H. Hellwig is an illegitimate, later homonym that has been applied to species included here in Baccharis. In key leads, references to pappi are to pappi on cypselae (i.e., in pistillate heads). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 20, p. 31. | FNA vol. 20, p. 23. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Astereae > Baccharis | Asteraceae > tribe Astereae | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | Molina salicifolia, B. viminea, B. viminea var. atwoodii | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | (Ruiz & Pavón) Persoon: Syn. Pl. 2: 425. (1807) | Linnaeus: Sp. Pl. 2: 860. (1753): Gen. Pl. ed. 5, 370. (1754) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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