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.

CENTAUREA

KNAPWEED, STAR-THISTLE

David J. Keil and Charles E. Turner

Annual to perennial herb, ± branched
Leaves alternate; lower generally deeply 1–2-lobed, segments generally narrow; upper reduced
Inflorescence: heads discoid (sterile outer flowers sometimes ± ray-like); involucre cylindric to hemispheric; phyllaries many, graded, generally ± ovate, scarious-margined, tip appendages fringed to spiny; receptacle flat, long-bristly
Flowers: inner fruiting; anther bases tailed, tips oblong; style top minutely hairy, tips minutely branched
Fruit ± barrel-shaped, ± compressed, attached ± at side; pappus generally of stiff, unequal bristles or narrow scales
Species in genus: ± 500 species: especially Eurasia, n Africa (± 2 North America); some cultivated (waifs may including C. cineraria L., C. eriophora L., C. jacea L., C. moschata L., C. muricata L., C. salmantica L.)
Etymology: (Greek: ancient name)
Weedy.

Introduced

C. X moncktonii C.E. Britton

Perennial 3–10 dm, ± soft-crinkly-hairy, becoming ± glabrous
Leaves: lower 5–25 cm, entire to irregularly lobed
Inflorescence ± flat-topped; heads few; involucre 15–18 mm, hemispheric; main phyllaries ± brown, appendages fringed with tapered teeth
Flowers many; corollas 15–22 mm, purple, sterile corollas ± ray-like
Fruit 2.5–3 mm, tan, finely hairy; pappus scales ± 0.5 mm
Chromosomes: 2n=44
Ecology:
Elevation:
Bioregional distribution: Northwestern California, s San Francisco Bay Area
Distribution outside California: native to Europe
Variable; ± stable hybrid (C. nigra X C. jacea—the latter a waif in NW).