Duration: Perennial

Nativity: Native

Lifeform: Subshrub

General: Herbaceous to shrubby perennials, to 2 m tall, stems often sprawling, current growth much branched, herbage with rough, minutely barbed hairs appressed downwards, usually woody only at the base.

Leaves: Alternate, broad at the base and sessile, lanceolate to deltate-ovate, 4-45 mm long, with acute to acuminate tips, margins entire to few-toothed, those of the branches markedly smaller that those of main axis.

Flowers: Small and creamy white with 5 connate petals, these roughly deltate in shape, 2.5-6.5 mm long, with adherent claws fused for the upper one-fifth, stamens 5, 6-10 mm long, well exserted, styles 3-11 mm long, ovaries ovoid, stigmas 1, flowers with 3 subtending bracts, the outer 1 larger than the inner 2, outer bracts deltate-ovate, 4-7.5 mm long, inner bracts lanceolate to ovate, 2-3 mm long, bases tapered to cordate, tips acute to acuminate or abruptly attenuate, margins crenate or lobed, infloresences in dense clusters in terminal racemes to 10 cm long and 1.5 cm wide, flowers borne on pedicles less than 1 mm long.

Fruits: Ovoid achenes, generally 5-veined or -ribbed, erect. Seeds 1 per achene, fusiform, 1.5-2.5 mm long, fusiform, with smooth surfaces.

Ecology: Found on sandy or gravelly dunes, in washes, canyons, and creosote-bush scrub communities, to 4,000 ft (1219 m); flowering May-July.

Distribution: Arizona, California, Nevada.

Ethnobotany: Unknown.

Synonyms: None

Editor: LCrumbacher2012

Etymology: Petalonyx from the Greek petalon, "petal," and onyx, "claw," thus claw-petalled, and thurberi is named after Dr. George Thurber (1821-1890), called the most accomplished horticulturist in America, and botanist and quartermaster of the Mexican Boundary Survey, 1850-1854.