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FNA | Family List | FNA Vol. 20 | Asteraceae | Baccharis

15. Baccharis salicina Torrey & A. Gray, Fl. N. Amer. 2: 258. 1842.

Willow-baccharis, Great Plains false willow

Baccharis salicifolia Nuttall, Trans. Amer. Philos. Soc., n. s. 7: 337. 1840, not (Ruiz & Pavón) Persoon 1807; B. emoryi A. Gray

Shrubs, 100–300 cm (much branched). Stems ascending, striate-angled, glabrous, smooth or minutely roughened, resinous. Leaves present at flowering (numerous and well developed); short-petiolate; blades (at least broader distinctly 3-nerved) oblong to oblanceolate, 25–70 × 5–10(–20) mm, bases tapering attenuate, margins usually serrate distally (teeth 1–3, coarse irregular, ca. 5 mm apart), sometimes entire, apices acute or obtuse, faces finely gland-dotted. Heads (100–200+, short-pedunculate or sessile) in (large, crowded, leafy) paniculiform arrays. Involucres narrowly obconic to campanulate; staminate 4–7 mm, pistillate 5–9 mm. Phyllaries lanceolate , 2–6 mm, margins scarious, medians green or reddish, apices greenish or purplish, often erose-ciliate, faces glabrous, gland-dotted, resinous . Staminate florets 20–25; corollas 3–5 mm. Pistillate florets 25–30; corollas 3–4 mm. Cypselae 1.2–2 mm, irregularly 8–10-nerved, glabrous; pappi 8–12 mm (elongating in fruit).

Flowering May–Nov. Stream banks, alkaline meadows, roadsides; 300–1600 m; Ariz., Calif., Colo., Kans., Nev., N.Mex., Okla., Tex., Utah; Mexico (Baja California, Chihuahua, Coahuila, Durango, Sonora).

Baccharis salicina is recognized by its narrow, gland-dotted leaves with 1–3 irregular teeth on the distal half, heads in loose leafy arrays, campanulate involucres, and cypselae with 8–10 ribs.

The recognition of Baccharis emoryi as a separate species in other floras has been based on its wider, glabrous, eglandular leaves, more cylindric pistillate involucres, and dense whitish pappi. It was said to occur both west of the Rocky Mountains and in western Texas. In our study, expressions of the characters used to distinguish B. emoryi from other species were found to be inconsistent and inadequate to warrant recognition as a distinct species. There appears to be a complex of up to four species—emoryi, salicina, neglecta and angustifolia—that intergrade from west to east. Characteristics progress from broader leaves and larger heads (emoryi form of salicina) to narrow leaves with small heads (neglecta, angustifolia). The delimitation of taxa within this complex merits further investigation.


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