©The World Botanical Associates Web Page
Prepared by Richard W. Spjut
December 2004


Petalonyx nitidus
Las Vegas, NV
May 1980

Petalonyx parryi
Muddy Mts, NV
May 1980


Petalonyx thurberi
Clark Co., NV
Nov 1979




Trees and Shrubs of Kern County (Jan 2013)    

     Petalonyx Subshrubs with Velcro or scabrous barbed hairs; stems often white when dormant; leaves simple, alternate, persistent; flowers white to cream in terminal clusters, with 5 spreading lobes and claws united below into a tube surrounded by a yellowish green 5-lobed calyx; stamens 5, exceeding petals; ovary inferior with 1carpel, 1 style, 1 stigma and 1 locule with 1 apical pendulous ovule, breaking apart irregularly at maturity; fruit an utricle, 5-ribbed.

Key to Petalonyx

Leaves with petioles, green to shiny green, often with conspicuous
scattered marginal teeth, not notably smaller up the stem........ Petalonyx nitidus

Leaf blades directly attached to stem, yellowish green, entire or
obscurely toothed along margins, notably smaller in size from base
to base of flowering stem.. ..................................................... Petalonyx thurberi


Petalonyx nitidus S. Watson 1873.  Shining sandpaper plant. Small subshrub, 15–30 cm; leaves green, or shiny green, triangular from a short petiole 2–6 mm, the blade portion 1.5–4 cm, usually with some scattered teeth along margins, teeth often developing irregularly; flowers May-Aug, 5–10 mm long; utricle 1–3 mm. Desert slopes and mesas, frequently on volcanic substrates; creosote scrub, Joshua tree and pinyon juniper woodlands, 3.000-6,500 ft; mostly Mojave Desert, southern Utah to central Arizona, across southern Nevada to eastern California. Type from southern NV.  Kern Co.: Jawbone Canyon (Mary DeDecker, 30 May 1974), Red Rock Canyon (F. W. Peirson, 29 May 1927), 1,003–1,037 m (CCH).

Petalonyx thurberi A. Gray 1854.  Common sandpaper plant. A much-branched subshrub 30–75 cm high and broad, young stems green, becoming white with age, with stiff downward pointing hairs; leaves short triangular (6–25 mm), directly attached to stem (no petiole); flowering after rain, but mainly in the spring and early summer (May–Jul); flowers white; fruit opening irregularly (utricle).  Common in sandy washes below 4500 ft, Mojave and Sonoran Deserts. Type from the Valley of the Gila River, AZ. Kern Co.: Considered rare by Twisselmann; however, observed by the author as occasional along old Hwy 14 between turnoff to Ridgecrest and Hwy 178, the northernmost range of the subspecies; also in Red Rock Canyon, Jawbone Canyon, and Chimney Creek Canyon north of South Fork Valley, 700–1,200 m (CCH).  Petalonyx gilmannii Munz 1938, treated as a subspecies of P. thurberi by some authorities, differs by the heart-shaped leaves and by flowering in the fall as well as in the spring; it is endemic to the Death Valley region, occurring at lower elevations (457–915 m) in washes with  Atriplex hymenelytra, Hymenoclea salsola and Ericameria paniculata.