214b. Symphyotrichum Nees subg. Astropolium (Nuttall) Semple in J. C. Semple et al., Cult. Native Asters Ontario. 133. 2002.
Tripolium Nees subg. Astropolium Nuttall, Trans. Amer. Philos. Soc., n. s. 7: 295. 1840; Aster Linnaeus sect. Hesterastrum Bentham; Aster sect. Oxytripolium (de Candolle) Torrey & A. Gray; Conyzanthus Tamamschjan; Symphyotrichum sect. Oxytripolium (de Candolle) G. L. Nesom; Tripolium Nees sect. Oxytripolium de Candolle
Annuals or perennials eglandular; taprooted or rhizomatous. Stems not brittle at maturity, glabrous or glabrate, sometimes sparsely hairy in leaf axils. Leaves: basal withering by flowering, petiolate, blades 1-nerved, spatulate to ovate or obovate, margins entire or shallowly serrate or crenate; cauline subpetiolate or sessile, blades narrowly lanceolate, linear, or subulate, bases attenuate, slightly sheathing, or ± clasping. Heads radiate. Phyllaries unequal (bases indurate), green zones narrowly lanceolate, spatulate to oblanceolate-rhombic, or rhombic (faces glabrous or sparsely hairy). Ray florets 10–30(–54) in 1 series; laminae (1.3–)5–8.5(–9.5) × (0.2–)1.2–2 mm. Disc corollas sometimes weakly ampliate, throats funnelform, lobes ± erect or ± spreading. Cypselae narrowly obovoid to fusiform, sometimes ± compressed, 5–6-nerved, sparsely strigillose or glabrate. x = 5.
Species ca. 10 (3 in the flora): North America; introduced worldwide.
SELECTED REFERENCE
Sundberg, S. D. 1986. The Systematics of Aster Subgenus Oxytripolium (Compositae) and Historically Allied Species. Ph.D. dissertation. University of Texas.
