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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. hydrophilum (Greene) Jeps.

Biennial (or short-lived perennial herb) 1–2.1 m
Stem ± cobwebby, becoming glabrous
Leaves thinly cobwebby-tomentose (both surfaces) or becoming glabrous above; lower 3–9 dm, petiole spine-margined, blade generally ± lobed, lobes generally with 2–4(6) wide 2° lobes or coarse teeth, main spines 2–9 mm; middle and upper smaller, clasping or short-decurrent with ear-like bases, uppermost much reduced, generally very spiny, lobes narrower
Inflorescence: heads solitary or in small groups in ± open cymes or panicle-like clusters; peduncles 0–6 cm; involucres 1.5–2.5 cm, 1.5–3 cm diam, ovoid to bell-shaped, thinly cobwebby, becoming glabrous; outer and middle ovate to ovate-lanceolate, minutely spiny-ciliate, appressed, midribs with narrow sticky glandular area, spines 1–3 mm, spreading, inner linear-lanceolate or oblong, tips flat, ± twisted
Flowers: corollas 18–23 mm, pale rose-purple, tube 8–10 mm, throat 5–6 mm, lobes 5–7 mm
Fruit 4–5 mm, dark brown to black, ± thick; pappus ± 15 mm
Ecology: Wet soils
Elevation: < 450 m.
Bioregional distribution: Deltaic Great Central Valley, n San Francisco Bay Area. Related to C. douglasii and C. mohavense.

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bioregional map for CIRSIUM%20hydrophilum being generated
 


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