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  • Up-to-date information about California vascular plants is available from the Jepson eFlora.

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.

CONYZA

Annual or perennial herb
Stems generally erect, leafy
Leaves alternate, linear to ± (ob)lanceolate, entire to pinnately dissected, obtuse to acute
Inflorescence: heads generally disciform (or minutely radiate), generally many in raceme- or panicle-like clusters; phyllaries in 2–3 equal or unequal series, free, linear to lanceolate, often narrowly scarious-margined, reflexed in age; receptacle naked
Pistillate flowers generally many; corollas white, pink, or cream, narrowly cylindric
Disk flowers ± few; corollas generally yellow, lobes short-triangular; style tips lanceolate, included or short-exserted
Fruit elliptic, compressed, puberulent; pappus of bristles
Species in genus: ± 50 species: especially tropical
Etymology: (Greek: flea; name of Pliny & Dioscorides for a fleabane)
Descended from within Erigeron [Noyes 2000 Plant Syst Evol 220:93–114]

Native

C. canadensis (L.) Cronquist

HORSEWEED

Annual 1–20(30) dm
Stem generally simple below, much-branched above, strigose or stiff-spreading-hairy
Leaves 1–10 cm, entire to shallowly few-lobed, glabrous to strigose, often ciliate
Inflorescence: heads obscurely radiate; lateral clusters not overtopping central; fresh involucre generally 2.5–4 mm diam; phyllaries 1–3.5 mm, glabrous to strigose, midvein resin-filled, orange when dry
Pistillate flowers 20–40; corollas 2.5–3 mm, ligule < 1 mm
Disk flowers 7–13; corollas 2.5–3 mm
Fruit ± 1.5 mm; pappus 2.5–3 mm, generally whitish in age
Chromosomes: 2n=18,36,54
Ecology: Common. Waste ground
Elevation: generally < 2000 m.
Bioregional distribution: California
Distribution outside California: ± worldwide
Flowering time: Jun–Sep

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