Helianthus arizonensis R.C. Jackson
Family: Asteraceae
Arizona sunflower
[Helianthus arizonicus R.C. Jacks.]
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Perennials, 20-30 cm (roots creeping). Stems erect to ascending, glabrous (glaucous). Leaves cauline; opposite; sessile; blades (bluish green) lanceolate, 2-7 × 0.5-1.3 cm, bases cuneate, margins entire (undulate), faces glabrous (glaucous). Heads 1-7. Peduncles 2-7.5 cm. Involucres hemispheric, 9-18 mm diam. Phyllaries 16-19, lance-ovate, 3.5-7 × 2-2.8 mm, (margins ciliate) apices acute, abaxial faces glabrate, sparingly gland-dotted. Paleae 5.5-6.5 mm, 3-toothed (apices acute, gland-dotted). Ray florets 10-14; laminae 7-9 mm. Disc florets 30+; corollas 3-3.5 mm, lobes yellow; anthers reddish brown, appendages brownish. Cypselae 2.8-3.2 mm, glabrous; pappi of 2 deltate, erose scales 1-1.7 mm. 2n = 34, 51. Flowering summer-fall. Open pine woodlands; 1200-2100 m; Ariz., N.Mex. Helianthus arizonensis is morphologically similar to the polyploid H. ciliaris; H. arizonensis is diploid (or triploid) and has entirely yellow disc corollas. It is known from relatively few sites.

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This project made possible by National Science Foundation Award 1410069