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©Copyright 1993 by the Regents of the University of California

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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.

ARCTIUM

BURDOCK

David J. Keil and Charles E. Turner

Biennial
Stems 1–several, branched above
Leaves basal and cauline, alternate, long-petioled, widely ovate; base deeply cordate; margin entire or toothed, gradually reduced upward in CA
Inflorescence: heads discoid, in leafy-bracted clusters; involucre ± spheric; phyllaries overlapping in many series, ± linear in CA, bases appressed, tips stiffly radiating, hooked-spiny; receptacle bristly
Flowers many; corolla pink to ± purple, lobes narrowly triangular; anther base tailed, tips ovate, acute to obtuse; style branched just above hairy ring, branches oblong, obtuse
Fruit ± compressed, rough or ribbed, glabrous, attachment basal; pappus several series of rough bristles, readily deciduous
Species in genus: 10 species: Eurasia
Etymology: (Greek: bear)

Introduced

A. minus (Hill) Bernh.

Plant < 15 dm
Stem: branches stiffly ascending
Leaf: blade < 40+ cm, green, puberulent or soft-hairy above, becoming glabrous, ± gray-tomentose below
Inflorescence: heads sessile to short-peduncled in raceme- or panicle-like clusters; involucre 10–25 mm diam; inner phyllaries generally purple-tinged, margins minutely serrate
Flower: corolla 8–10 mm
Fruit 4–7.5 mm, dark brown or dark-spotted; pappus ± 2 mm
Chromosomes: 2n=32,36
Ecology: Disturbed places
Elevation: < 1200 m.
Bioregional distribution: Northwestern California
Distribution outside California: native to Europe

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