Helianthus paradoxus
Rhodora 60: 272, fig. 1. 1958.
Annuals, 130–200 cm. Stems erect, glabrous or ± hispid. Leaves mostly cauline; opposite (proximal) or mostly alternate; petioles 1.5–6 cm; blades lanceolate to lanceovate, 7–17.5 × 1.7–8.5 cm, bases cuneate, margins entire or (larger leaves) toothed, abaxial faces ± scabrous, not glanddotted. Heads 1–5. Peduncles 12–18 cm. Involucres hemispheric, 15–20 mm diam. Phyllaries 15–25, lanceolate to lanceovate, 6–19 × 0.7–4 mm (equaling or slightly surpassing discs), (margins ciliate) apices (spreading to recurved) acuminate, abaxial faces usually glabrate or sparsely hispid. Paleae 8–9 mm, apices 3-toothed (apices glabrous). Ray-florets 12–20; laminae 20–30 mm. Disc-florets 50+; corollas 5–5.5 mm, lobes reddish; anthers dark, appendages yellowish or dark (style-branches reddish). Cypselae 3–4 mm, glabrous; pappi of 2 lanceolate scales 2.5–2.9 mm. 2n = 34.
Phenology: Flowering late summer–fall.
Habitat: Saturated saline soils, desert wetlands
Elevation: 1000–1200 m
Discussion
Of conservation concern.
Helianthus paradoxus is listed by the U.S. Fish and Wildlife Service as an endangered species and is in the Center for Plant Conservation’s National Collection of Endangered Plants. It is of hybrid origin; the parents are H. annuus and H. petiolaris (L. H. Rieseberg et al. 1990). It occupies a different habitat type than either parent (H. annuus usually on clay-based mesic soils and H. petiolaris usually on dry, sandy soils).
Selected References
None.