Hesperidanthus argillaceus

Perennials. Stems simple or few from caudex, erect, (few-branched distally), 1.3-3 dm. Leaves subsessile; blade linear or linear-lanceolate, 0.9-4 cm × (0.8-)1-3(-6) mm, base cuneate to attenuate, margins entire, apex acute. Racemes 5+-flowered. Fruiting pedicels suberect, ascending, or divaricate, straight or curved upward, 7-18 mm. Flowers: sepals purple, 4.2-6.5 × ca. 1.5 mm; petals white or lilac (with darker purple veins), 8-11 × 2.5-4 mm, claw undifferentiated from blade; filaments 1.5-2.5 mm; anthers oblong, 1-1.5 mm; gynophore 0-0.3 mm. Fruits curved, terete, 1.8-5.5 cm × 1-1.2 mm; ovules 54-62 per ovary; style subclavate, 0.5-2 mm; stigma flat, obscurely 2-lobed. Seeds 1.5-1.8 × 0.7-0.9 mm.

Flowering Apr-Jun. Desert shrub or sagebrush communities, rocky slopes, shale barrens; of conservation concern; 1400-1800 m; Utah.

Hesperidanthus argillaceus is restricted to the Uinta and upper Green River shale formation in Uintah County.