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. neomexicanum A. Gray

DESERT THISTLE

Biennial (or short-lived perennial herb) 4–29 dm
Stem generally 1, generally simple below; branches few above, ascending, ± white-cobwebby-tomentose, puberulent
Leaves ± persistently gray-tomentose (both surfaces), lighter below; lower 6–35 cm, petioled or tapered to spiny-winged base, oblong-elliptic to oblanceolate, ± lobed, lobes generally rigidly spreading, simple or with 2–4 coarse teeth or 2° lobes, main spines 5–15 mm; middle and upper generally smaller, narrower, decurrent as spiny wings, uppermost well separated, much reduced, ± bract-like, sometimes barely a cluster of long spines
Inflorescence: heads 1–few in open cyme-like clusters (sometimes on short axillary branches); peduncles 2.5–30 cm, leafy; involucres 2–2.5 cm, 2.5–5 cm diam, hemispheric or bell-shaped, ± loosely tomentose, sometimes glabrous; phyllaries linear-lanceolate, entire, sometimes midveins with glandular area, outer and middle spreading to reflexed, spines 4–15 mm, inner with tips ± erect, flat
Flowers: corollas 18–27 mm, white to pale lavender or pink, tube 8–14 mm, throat 4–7 mm, lobes 5–9 mm
Fruit 5–6 mm, dark brown, ± flattened; pappus 15–20 mm
Chromosomes: 2n=30
Ecology: Canyons, slopes, roadsides
Elevation: 800–2100 m.
Bioregional distribution: eastern Mojave Desert
Distribution outside California: to Colorado, New Mexico
Flowering time: Apr–May
Closely related to C. occidentale.