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.

AMBROSIA

RAGWEED, BUR-SAGE

Willard W. Payne

Annual to shrub, monoecious
Leaves often opposite below, generally alternate above, generally petioled, hairy, glandular
Inflorescence: staminate heads generally many in ± spikes or racemes, phyllaries fused into shallow cup; pistillate heads generally clustered below staminate, generally spiny, bur-like; involucre ± 0; receptacle chaffy; chaff scales spirally arrayed, fused below, tips generally becoming spiny; each pistillate flower in separate chamber
Staminate flowers ± many; corolla yellow or translucent; anthers free; style unbranched
Pistillate flowers 1–5; corolla 0; style branches long
Fruit enclosed in bur; pappus 0
Etymology: (Greek: early name for aromatic plants; the mythic food of the gods)
[Payne 1976 Plant Syst Evol 125:169–178] Closely related to (indistinct from) Hymenoclea [Miao et al. 1995 Amer J Bot 82:924–932; Baldwin et al. 1996 Madroño 43:15–27] Wind-blown pollen often highly allergenic.

Native

A. acanthicarpa Hook.

ANNUAL BUR-SAGE

Annual 4–15 dm, from slender taproot
Stem gray-green, ± stiffly strigose-bristly
Leaves: petioles winged; blade pinnately divided, < 8 cm, 7 cm wide
Inflorescence: staminate heads 2–5 mm diam, involucre lobes 3–9, tips of longest 3 ± black-lined along midveins; pistillate heads 1-flowered
Fruit: body of bur 5–7 mm, ovoid, generally ± golden, glabrous or puberulent; spines 0–30, scattered, flat, straight, sharp
Chromosomes: 2n=36
Ecology: Sandy plains, disturbed sites, many communities
Elevation: < 2200 m.
Bioregional distribution: North Coast Ranges, Sierra Nevada, San Joaquin Valley, Central Coast, South Coast Ranges, Southwestern California, Great Basin Floristic Province, Desert
Distribution outside California: to Washington, Montana, Wyoming, Texas, nw Mexico
Flowering time: Aug–Nov
Synonyms: Franseria a. (Hook.) Coville