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.

ACHILLEA

YARROW, MILFOIL

Perennial, strongly scented
Leaves alternate, simple to 3-pinnately dissected, ± hairy, ± reduced upward
Inflorescence: heads generally radiate, many, in flat-topped clusters; involucre bell-shaped or ovoid; phyllaries graded in 3–4 unequal series, ovate, obtuse; margins membranous; receptacle flat to rounded; chaff scales narrow, transparent
Ray flowers few; ligules short, round, white, pink, or yellow
Disk flowers ± many; corollas short, white to purple or yellow
Fruit oblong to obovate, compressed, thick-margined, glabrous; pappus 0
Species in genus: ± 85 species: North America, Eurasia, n Africa
Etymology: (Greek: Achilles of ancient mythology)
Reference: [Tyrl 1975 Brittonia 27:187–196]

Native

A. millefolium L.

Plant 10–200 cm
Leaves very finely 3-pinnately divided; cauline leaves ± clasping
Inflorescence: phyllaries 4–9 mm
Ray flowers generally 3–8; ligules 2.5–4 mm, ovate to round, white to pink
Disk flowers 15–40; corollas 2–3 mm, white to pink
Fruit ± 2 mm
Chromosomes: 2n=36,45,54,63,72
Ecology: Many habitats
Elevation: < 3500 m.
Bioregional distribution: California Floristic Province, Great Basin Floristic Province
Distribution outside California: circumboreal
Flowering time: Summer
Synonyms: A. borealis Bong. subspp. arenicola (A. Heller) D.D. Keck, californica (Pollard) D.D. Keck; A. lanulosa Nutt. subspp. alpicola (Rydb.) D.D. Keck, lanulosa; A. m. vars. alpicola (Rydb.) Garrett, arenicola (A. Heller) Nobs, borealis (Bong.) Farwell, californica (Pollard) Jeps., gigantea (Pollard) Nobs, lanulosa (Nutt.) Piper, littoralis Nobs, pacifica (Rydb.) G.N. Jones, puberula (Rydb.) Nobs
Highly variable polyploid complex; leaf size and hairiness especially variable
Horticultural information: SUN, DRN: 4, 5, 6, 17 &IRR: 1, 2, 3, 7, 8, 9, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24 &part SHD: 10, 11, 12, 13; GRCVR; CVS; rather INV; also STBL.