Gen. Sp. Pl., 30. 1816.
Annuals, perennials, or subshrubs, 10–150 (–200) cm (taprooted). Stems erect to ascending, usually branched, glabrous or papillate-scabrous to minutely hispidulous or scabro-hirtellous. Leaves basal (persistent or absent at flowering) and cauline; alternate; sessile or petiolate (decurrent); blades (1–5-nerved) linear to lanceolate or spatulate, margins entire (sometimes scabroso-ciliate), faces glabrous or minutely hairy, gland-dotted (sometimes obscurely), resinous. Heads radiate, borne singly or (3–6) in clusters or glomerules. Involucres cylindric to campanulate, (2–11.5 ×) 0.8–7.5 mm. Phyllaries 4–40 in 2–4 series (stramineous), 1-nerved or 3-nerved, (sometimes strongly convex or keeled), ovate to lanceolate, unequal, bases white-indurate, margins narrowly scarious, abaxial faces glabrous or sparsely hispidulous or hirtellous. Receptacles flat to conic, pitted (hairy, hairs 1-seriate, swollen, apically hooked), epaleate. Ray-florets 1–30, pistillate, fertile; corollas yellow or white (laminae coiling). Disc-florets 1–150, bisexual, fertile, sometimes functionally staminate; corollas yellow or white, tubes shorter than funnelform throats, lobes 5, erect, short-deltate; style-branch appendages linear-lanceolate. Cypselae (light tan to purplish black) clavate or cylindric, not compressed, 5–8-nerved, hairy (glabrous in G. wrightii; hairs white, usually arising primarily from between ribs, appearing to occur in longitudinal lines, usually obscuring faces, apices acute or blunt with terminal cells slightly divergent, or clavate to bulbous); pappi persistent or readily falling, coroniform or of 5–10 whitish, irregular, sometimes ± connate, often erose-margined, scales in 1–2 series (usually longer in discs than rays). x = 4.
w North America, w South America
Species 28 (10 in the flora).
Amphiachyris sometimes has been placed within Gutierrezia; it was treated as distinct by M. A. Lane (1982). The monotypic genus Thurovia from southeast Texas was included in Gutierrezia by Lane; recent molecular data support its status as a separate genus. Evidence from Y. Suh and B. B. Simpson (1990) suggested that Amphiachyris and Thurovia form the sister group to Gutierrezia. The taxonomic history of Gutierrezia also has been intertwined with species of Xanthocephalum, a genus superficially similar to Gutierrezia but more closely related to Grindelia and Isocoma.
Gutierrezia is recognized by its taprooted habit, gland-dotted leaves, small heads, receptacles with fimbriate pit borders, funnelform disc corollas, clavate-hairy cypselae, pappi coroniform or of scales, and base chromosome number of x = 4. Polyploidy is common but of little taxonomic significance; polyploids of different levels tend to be scattered through the range of a species, and populations often comprise mixtures of individuals of different euploid levels (M. A. Lane 1985).
|1||Perennials or subshrubs||> 5|
|2||Cauline leaves (1–)3–5-nerved, proximal usually persistent at flowering; phyllary apices conduplicate, swollen, appearing abaxially keeled; cypsela faces pebbly or warty with raised oil cavities, glabrous||Gutierrezia wrightii|
|2||Cauline leaves 1-nerved (sometimes 3-nerved in G. texana), proximal usually absent at flowering; phyllary apices flat; cypsela faces moderately to densely hairy, never with oil cavities||> 3|
|3||Involucres 4–7 mm diam.; ray corollas white, drying light yellow or reddish; pappi obscured by cypsela indument; cypsela hairs with bulbous-capitate apices||Gutierrezia arizonica|
|3||Involucres 2–5 mm diam.; ray corollas yellow; pappi not hidden by cypsela indument; cypsela hairs with acute to clavate apices||> 4|
|4||Stems smooth, glabrous; cypsela hairs with acute apices; pappi of scales or essentially absent||Gutierrezia texana|
|4||Stems papillate-scabrous, often sparsely so; cypsela hairs with clavate apices; pappi of scales||Gutierrezia sphaerocephala|
|5||Heads mostly sessile or subsessile, in glomerules, often in broad, dense, flat-topped arrays||> 6|
|5||Heads mostly pedunculate, in relatively open arrays||> 7|
|6||Involucres cylindric, 1–1.5 mm diam.; ray florets 1(–2); disc florets 1(–2), functionally staminate (corollas obdeltate-funnelform, throats widely flaring, lobes 1/3 corolla lengths, recurved-coiling)||Gutierrezia microcephala|
|6||Involucres cuneate-campanulate to cylindric, 1.5–2(–3) mm diam.; ray florets (2–)3–8; disc florets (2–)3–9, bisexual, fertile (corollas tubular-funnelform, lobes deltate and erect to spreading or recurved)||Gutierrezia sarothrae|
|7||Perennials; basal leaves persistent; ray corollas 5–8(–10) mm; disc florets 15–23||Gutierrezia petradoria|
|7||Subshrubs; basal leaves not persistent; ray corollas 2–7 mm; disc florets 5–15(–17)||> 8|
|8||Stems sparsely scabrous or glandular-scabrous to glabrate; phyllary apicesthickened; cypselae loosely strigose; Utah||Gutierrezia pomariensis|
|8||Stems glabrous or minutely hispidulous; phyllary apices not thickened; cypselae densely strigoso-sericeous; California and Arizona||> 9|
|9||Stems glabrous or minutely hispidulous; involucres turbinate to cylindro-turbinate (longer than diam.), 2.5–4 mm diam.; cypselae 2–2.8 mm;California||Gutierrezia californica|
|9||Stems glabrous; involucres narrowly campanulate lengths ± equaling diams., 3–4 mm diam.; cypselae 1–1.2 mm; Arizona||Gutierrezia serotina|
"[" is not declared as a valid unit of measurement for this property."]" is not declared as a valid unit of measurement for this property.