Annuals, 10–120 cm. Stems ± erect to prostrate. Leaves mostly cauline (at flowering); proximal opposite (often in winter–spring rosettes), most alternate; ± sessile; blades oblanceolate to linear or lance-linear, proximal usually 1–2-pinnatifid, ultimate margins toothed or entire (sometimes bristly-ciliate), (apices of distal leaves usually spine-tipped) faces glabrous, scabroso-hirtellous, ± hirsute, or villous, often glandular as well. Heads radiate, borne in glomerules or ± spiciform-paniculiform or ± umbelliform arrays. Peduncular bracts: pit-glands and tack-glands 0 (apices usually spine-tipped, sometimes apiculate). Involucres ± obconic or urceolate, 3–8+ mm diam. (subtended by calyculi of 5–12+ usually spine-tipped bractlets). Phyllaries falling or persistent, 5–75+ in 1 series (lanceolate to lance-attenuate or oblanceolate, herbaceous, each usually 1/2 enveloping subtended ray floret proximally, abaxially scabroso-hirtellous, hirsute, or villous and/or glandular, apices often spine-tipped). Receptacles flat to convex, setulose, paleate (paleae persistent, subtending all or most disc florets, distinct, phyllary-like, more scarious). Ray florets 5–75+, pistillate, fertile; corollas yellow. Disc florets 6–200+, usually functionally staminate, rarely bisexual and fertile; corollas yellow, tubes shorter than funnelform throats, lobes 5, deltate (anthers reddish to dark purple or yellow to brownish; styles glabrous proximal to branches). Ray cypselae ± compressed (abaxially gibbous, basal attachments basal or oblique, apices beaked or elevated adaxially, faces glabrous); pappi 0. Disc cypselae usually 0; pappi (of disc florets) 0 or of 3–12 linear, oblanceolate, or subulate scales. x = 13.

Distribution

w United States, nw Mexico.

Discussion

Species 4 (3 in the flora).

Following B. G. Baldwin (1999b), Centromadia is treated here as distinct from Hemizonia; Centromadia is more closely related to Calycadenia, Deinandra, Holocarpha, and Osmadenia than to Hemizonia in the strict sense (S. Carlquist et al. 2003). Taxa of Centromadia are self-incompatible and of low to high interfertility (C. S. Venkatesh 1958). Most occur in somewhat poorly drained or alkaline sites.

Selected References

None.

Lower Taxa

Centromadia fitchii, Centromadia parryi, Centromadia pungens

Key

1	Leaves not glandular; disc pappi 0	Centromadia pungens
1	Leaves sometimes glandular; disc pappi of 3–5 linear to subulate scales, or 8–12 narrowly oblanceolate to linear scales	> 2
2	Leaves densely villous or hirsute, stipitate-glandular (glands yellow, brown, or black); anthers reddish to dark purple; disc pappi of 8–12 linear or narrowly oblanceolatescales	Centromadia fitchii
2	Leaves glabrous, scabroso-hirtellous, ± hirsute to hirtellous, or villous, sometimes glandular (glands yellow); anthers yellow, brownish, or reddish to dark purple; discpappi of 3–5 linear to subulate scales	Centromadia parryi