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ASTERACEAE

SUNFLOWER FAMILY

David J. Keil, Family Editor and author, except as specified

Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1–many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1–many per head
Flowers bisexual, unisexual, or sterile, ± small, of several types; calyx 0 or modified into pappus of bristles, scales, or awns, which is generally persistent in fruit; corolla radial or bilateral (rarely 0), lobes generally (0)4–5; stamens 4–5, anthers generally fused into cylinder around style, often appendaged at tips, bases, or both, filaments generally free, generally attached to corolla near throat; pistil 1, ovary inferior, 1-chambered, 1-seeded, style 1, branches 2, generally hair-tufted at tip, stigmas 2, generally on inside of style branches
Fruit: achene, cylindric to ovoid, generally deciduous with pappus attached
Genera in family: ± 1300 genera, 21,000 species (largest family of dicots): worldwide. Largest family in CA. Also see tribal key to CA genera: Strother 1997 Madroño 44(1):1–28. See glossary p. 25 for illustrations of general family characteristics.

CIRSIUM

THISTLE

David J. Keil and Charles E. Turner

Annual to perennial herb (sometimes short-lived, dying after flowering once)
Stem generally erect
Leaves: lower generally tapered or petioled, often wavy-margined, generally pinnately lobed, ± dentate, lobes and teeth spine-tipped, margin generally spiny-ciliate, glabrous to tomentose; upper generally sessile, ± reduced
Inflorescence: heads discoid, 1–many; involucre cylindric to spheric; phyllaries many, graduated in several series, outer spine-tipped; receptacle flat, long-bristly
Flowers generally many; corollas ± bilateral, white to red or purple, tube long, slender, lobes linear; anther bases sharply sagittate, tips oblong; style tip with slightly swollen node, appendage (above node) long, cylindric, branches very short
Fruit ovoid, glabrous; scar slightly angled; pappus bristles many, plumose, ± persistent or falling in ring
Species in genus: ± 200 species: North America, Eurasia
Etymology: (Greek: thistle)
Taxa difficult, incompletely differentiated, hybridize.

Native

C. scariosum Nutt.

ELK THISTLE

Biennial (or short-lived perennial herb) 0.5–10+ dm
Stem often 0 or very short, sometimes erect, often ± fleshy, ridged, glabrous to loosely tomentose, sometimes coarse-hairy
Leaves often basal, glabrous to loosely tomentose above, glabrous to densely tomentose below; lower 1–4 dm, tapered or spiny-petioled, oblong to oblanceolate, subentire to deeply lobed, sometimes with 2° lobes or teeth, main spines generally 2–7 mm; cauline 0 or well distributed, ± petioled
Inflorescence: heads generally ± sessile in basal leaf rosette or in clusters at stem tips, generally closely subtended by leaves; involucres 2–4.5 cm, 2–5 cm diam, ovoid to bell-shaped, glabrous; phyllaries linear-lanceolate to ovate, entire to minutely toothed, outer tipped by ascending spines 2–5 mm, inner with tips entire or toothed, flat or crinkled
Flowers: corollas 23–32 mm, ± white to purple, tube 10–16 mm, throat 6–10 mm, lobes 5–6 mm
Fruit 3–5 mm, oblong-obovate, ± compressed; pappus 15–30 mm
Chromosomes: 2n=34
Ecology: Moist places, meadows
Elevation: (400)700–3400 m.
Bioregional distribution: Klamath Ranges, Cascade Range, Sierra Nevada, South Coast Ranges (very uncommon), Transverse Ranges, Peninsular Ranges, Great Basin Floristic Province
Distribution outside California: to British Columbia, Montana, Colorado, New Mexico, Baja California
Flowering time: Jun–Aug
Synonyms: C. drummondii Torr. & A. Gray & C. foliosum (Hook.) DC., misapplied; C. tioganum Congdon
Extremely variable, needing study; dwarf and tall plants sometimes occur together. Plants from SNE & SnBr, with stems 0, heads small, corollas purple, have been called C. congdonii R. Moore & Frankton.

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