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. occidentale (Nutt.) Jeps.

Biennial 1–30 dm, erect or low, mound-like
Stem generally 1, branched above (near base in dwarf plants), ± tomentose
Leaves ± densely gray- or whitish tomentose, especially below; lower 1–4 dm, petioles spiny-winged, blade oblanceolate, lobed 1/2+ to midvein, lobes widely triangular, dentate or further lobed, main spines 1–10 mm; upper gradually reduced, sessile, ± clasping or short-decurrent, linear or oblong, often entire, often spinier than lower, uppermost bract-like
Inflorescence: heads 1–several in loose to tight cluster (barely raised above rosette in dwarf plants); peduncles 1–30 cm; involucres 1.5–5 cm, 1.5–8 cm diam, ovoid to spheric; phyllaries ± equal to strongly graduated, linear or linear-lanceolate, straight, ascending and appressed to widely radiating, often connected side-to-side by conspicuous cobwebby hairs, spines 3–10+ mm, inner with tips flat, straight
Flowers: corollas 18–40 mm, white to purple or red, tube 8–18 mm, throat 5–7 mm, lobes 5–10 mm
Fruit 5–6 mm, shiny, ± brown; pappus 15–30 mm
Chromosomes: 2n=30
Ecology: Many habitats
Elevation: < 3600 m.
Bioregional distribution: California Floristic Province (except San Joaquin Valley), Modoc Plateau, White and Inyo Mountains, w Mojave Desert
Distribution outside California: to s Oregon, sw Idaho, w Nevada
Variable; ± distinctive, intergrading races often treated as sp.

Native

var. californicum (A. Gray) D.J. Keil & C.E. Turner

CALIFORNIA THISTLE

Plants generally 5–20 dm, erect
Leaves green to gray above, gray below
Inflorescence: heads short- to long-peduncled in ± open clusters, well elevated above lower leaves; involucre 1.5–5 cm diam, subglabrous to densely cobwebby; middle phyllary tips generally < 1 cm, sometimes much longer, 1–3 mm wide, appressed to loosely spreading or ascending, sometimes twisted
Flowers: corollas 18–35 mm, white to purple or rose (rarely red)
Chromosomes: 2n=28,30
Ecology: Often disturbed places, woodland, open forest
Elevation: < 2300 m.
Bioregional distribution: Sierra Nevada, c&s South Coast Ranges, Southwestern California
Synonyms: C. c. A. Gray; C. c. var. bernardinum (Greene) Petr
Intergrading with var. venustum in s SN & s SCoR; plants intermediate to var. candidissimum in n SN.