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. undulatum (Nutt.) Spreng.

WAVYLEAF THISTLE

Perennial 2.5–10 dm, from creeping (sometimes tuber-like) roots
Stem generally simple below, few-branched above, white-tomentose
Leaves gray-tomentose above, white- below; lower 15–30 cm, tapered to spiny petioles, elliptic to oblanceolate, ± shallowly lobed, lobes simple or with 2–4 narrow to wide 2° lobes or coarse teeth, main spines 2–4 mm, yellow; middle and upper gradually reduced, decurrent as spiny-margined wings, often spinier than lower, spines 2–10 mm
Inflorescence: heads 1–few in cymes; peduncles 0–15 cm, ± leafy; involucres 2–5 cm, 2–5 cm diam, ± ovoid to bell-shaped, ± loosely tomentose on phyllary margins, becoming glabrous; phyllaries strongly graduated (outer ovate, inner lance-oblong), entire or minutely roughened, tightly appressed, midribs of outer and middle glandular area, spines 2–5 mm, spreading to reflexed, inner with tips flat, erect or recurved, ± twisted
Flowers: corollas 25–50 mm, white to pale lavender or pink, tube 11–25 mm, throat 7–11 mm, lobes 7–15 mm
Fruit 4–7 mm, light brown, ± compressed; pappus 25–40 mm
Chromosomes: 2n=24,26
Ecology: Disturbed places
Elevation: < 1600 m.
Bioregional distribution: s Cascade Range, San Francisco Bay Area, s Outer South Coast Ranges, South Coast, Modoc Plateau
Distribution outside California: native to c US
Hybridizes with C. ochrocentrum. Weedy.