Arida riparia |
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alkali aster, Chiricahua Mountain tansy-aster |
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Habit | Annuals, 25–60 cm; taproots slender to thick. |
Stems | 1–12+, erect or ascending, straight and rigid, sometimes sprawling from base, branching from base and distally, glabrous, glaucous. |
Leaves | mostly cauline; sessile (± appressed); blades oblanceolate, 20–30 × 3–5 mm, reduced distally, (thick, succulent) bases broadened, margins entire (incised to dentate in hybrids with A. parviflora) eciliate or with 1–8 cilia per side, apices linear, spiny-mucronate, glabrous; distal subulate, entire. |
Involucres | hemispheric, 10–12 × 10–16 mm (fresh). |
Ray florets | 50–80+; laminae bluish purple to lavender, 10–12 mm, coiled after flowering. |
Disc florets | 45–100+; corollas yellow, 3.5–5 mm. |
Phyllaries | in 4–5 series, appressed, linear-lanceolate, 2–8 mm, bases whitish to tan, margins entire to laciniate, apices green, acute to acuminate, glabrous. |
Heads | borne singly (terminal), often in loose, leafy, cymiform arrays. |
Cypselae | oblanceoloid, 2.5–3 mm, 11–13-nerved per face, faces sparsely sericeous; pappi: white, setose; ray 3–3.5 mm; disc 3–4 mm. |
2n | = 10. |
Arida riparia |
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Phenology | Flowering Apr–Sep. |
Habitat | Low valleys, saline soils on mudflats, edges of playas |
Elevation | 1300–1400 m (4300–4600 ft) |
Distribution |
AZ; NM; Mexico (Chihuahua, Coahuila, Durango, Zacatecas) |
Discussion | Arida riparia is a distinctive species recognized by its V-shaped branching, narrow, succulent, somewhat appressed, spiny-tipped leaves, and relatively large heads. It is known to hybridize with A. parviflora in southeastern Arizona and adjacent New Mexico. Specimens with dentate leaf margins usually represent hybrids. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 20, p. 405. |
Parent taxa | |
Sibling taxa | |
Synonyms | Aster riparius, Machaeranthera riparia, Machaeranthera sonorae |
Name authority | (Kunth) D. R. Morgan & R. L. Hartman: Sida 20: 1414. (2003) |
Web links |