1. Helianthus porteri (A. Gray) Pruski, Castanea. 63: 75. 1998.
Rudbeckia porteri A. Gray, Mem. Amer. Acad. Arts, n. s. 4: 83. 1849; Heliomeris porteri (A. Gray) Cockerell; Viguiera porteri (A. Gray) S. F. Blake
Annuals, 40–100 cm. Stems erect, usually sparsely strigose, sometimes hispid as well. Leaves mostly cauline; opposite (proximal) or alternate; petioles 0–0.2 cm; blades (± 3-nerved distal to bases) narrowly lanceolate to linear, 5–11.5 × 0.15–1 cm, bases cuneate, margins entire (often ± ciliate proximally), faces sparsely strigose or scabrous to glabrate, sparsely gland-dotted. Heads usually 5+. Peduncles 1–10 cm. Involucres hemispheric, 5–6 mm diam. Phyllaries 11–17, linear, 5.5–8 × 0.8–1.3 mm (margins sparsely hispido-ciliate, hairs 0.5–1.2 mm), apices acute to acuminate, abaxial faces glabrate, not gland-dotted. Paleae (ovate) 3.5–4.6 mm, entire (1-toothed). Ray florets 7 –8; laminae (10–)15–20 mm. Disc florets 30+; corollas 2.8–3.5 mm, lobes yellow; anthers dark, appendages dark. Cypselae 2.2–2.3 mm, sparsely puberulent (bases and apices); pappi 0. 2n = 34.
Flowering fall. Granite outcrops; 200–500+ m; Ala., Ga., N.C., S.C.
Helianthus porteri was established at Rocky Face Mountain, North Carolina, following its introduction as part of an ecologic experiment. Where it occurs, H. porteri produces conspicuous massed floral displays when in bloom. It is remarkably similar morphologically in its reduced habit, epappose cypselae, conic receptacles, and unlobed, mucronate pales to Heliomeris (Viguiera sect. Heliomeris), and it is treated under Viguiera in most southeastern United States treatments; its style appendages and chromosome number agree with molecular phylogenetic data in placing it within Helianthus.