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.

Introduced

C. ochrocentrum A. Gray

YELLOWSPINE THISTLE

Perennial 2.5–10 dm; roots creeping
Stem generally simple below, few-branched above, white-tomentose
Leaves thinly gray-tomentose above, white-tomentose below; lower 10–25 cm, tapered to spiny petioles, elliptic to oblanceolate, deeply lobed, lobes generally rigidly spreading, simple or with 2–4 ± narrow 2° lobes or coarse teeth, main spines 3–10 mm; middle and upper gradually reduced, decurrent as spiny-margined wings, generally very spiny, spines 5–15 mm
Inflorescence: heads 1–few in cymes; peduncles 0–10 cm, leafy; involucres 2.5–3.5 cm, 2–3.5 cm diam, ± ovoid to bell-shaped, ± loosely tomentose, becoming glabrous; phyllaries strongly graduated (outer ovate, inner oblong), minutely roughened or toothed, tightly appressed, midribs of middle phyllaries often with glandular area, spines 5–12 mm, stout, spreading to reflexed, inner with tips erect or recurved, ± twisted, flat, sometimes ± expanded and fringed
Flowers: corollas 29–37 mm, white to pale lavender or pink, tube 14–17 mm, throat 7–10 mm, lobes 8–11 mm
Fruit 7–8 mm, light brown, ± thick; pappus 25–30 mm
Chromosomes: 2n=15,16,17
Ecology: Disturbed places, fields
Elevation: < 1700 m.
Bioregional distribution: n North Coast, Klamath Ranges, e Sierra Nevada, n Channel Islands, Transverse Ranges, Peninsular Ranges, Modoc Plateau, White and Inyo Mountains
Distribution outside California: native to c US
Flowering time: Apr–Jul
Hybridizes with C. undulatum. Weedy.