Chorizanthe R.Br. ex Benth. is a genus of small annual herbs and subshrubs in the buckwheat family (Polygonaceae, subfamily Eriogonoideae), commonly known as spineflowers. The genus comprises around 61 accepted species (some authorities recognise up to 105 descendant taxa including infraspecific ranks) distributed across western North America and South America.
Plants grow with a slender to stout taproot and stems that are prostrate, decumbent, or erect, typically pubescent. Leaves are basal and rosulate or cauline, with blades that are linear to oblanceolate or spatulate. The inflorescences are terminal, cymose or capitate, and trichotomously or dichotomously branched. A hallmark of the genus is the involucre: a tubular to campanulate structure bearing 3–6 teeth each tipped with a stiff awn, giving the plant its characteristic spiny appearance and its common name. Flowers are bisexual, ranging in colour from white to yellow, pink, rose-pink, red, maroon, or purple, with 3, 6, or 9 stamens. Fruits are lenticular or 3-angled achenes. When dried, the inflorescences form rounded, prickly husks that persist long after seed dispersal.
The genus belongs to the order Caryophyllales and is placed within Polygonaceae. Three genera have been treated as synonyms: Acanthogonum Torr. (1857), Eriogonella Goodman (1934), and Trigonocarpus Bertero ex Steud. (1841). The primary taxonomic treatment for North American species is James L. Reveal's account in Flora of North America volume 5. The genus name derives from the Greek chorizo (to divide) and anthos (flower), referring to the distinctively divided calyx lobes.
Etymology
The genus name Chorizanthe is formed from two Greek roots: chorizo, meaning "to divide," and anthos, meaning "flower." The combined sense — "divided flower" — refers specifically to the divided or cleft calyx lobes that are a defining structural feature of the genus, rather than to any division of the petals. The authorship is attributed to R. Brown ex Bentham.
Distribution
Spineflowers occur in western North America and South America. In North America the genus is concentrated in the southwestern United States, with notable representation in the Sonoran Desert and the Colorado Plateau region. The SEINet portal, which covers the Arizona–New Mexico area and broader southwestern flora, lists over 50 species for the region. Several species have restricted ranges and are of conservation concern within California and adjacent states.
Ecology
Plants in Chorizanthe are predominantly annuals with taproots, adapted to dry, often sandy or rocky substrates characteristic of western North American deserts and semi-arid shrublands. The spiny, awn-tipped involucres likely function in seed dispersal by adhering to passing animals or clothing. The wide range of flower colours — white, yellow, pink, red, maroon, and purple — across species suggests diverse pollinator associations within the genus.
Taxonomy
Chorizanthe R.Br. ex Benth. is the accepted name in the GBIF Taxonomic Backbone, placed in family Polygonaceae (order Caryophyllales, kingdom Plantae). Three genera are treated as synonyms: Acanthogonum Torr. (published 1857 in Pacif. Railr. Rep. Whipple), Eriogonella Goodman (published 1934 in Ann. Missouri Bot. Gard.), and Trigonocarpus Bertero ex Steud. (published 1841 in Nomencl. Bot. ed. 2). Wikipedia also places the genus in subfamily Eriogonoideae. The primary North American taxonomic authority is James L. Reveal's treatment in Flora of North America volume 5, referenced by the SEINet portal. Within GBIF, at least two taxa — Chorizanthe brevicornu Nutt. 1859 and Chorizanthe floccosa M.E.Jones — are flagged as DOUBTFUL, the former as a possible variant of C. brevicornu Torr.
