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Achyronychia cooperi
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Frost-mat Onyx Flower
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Achyronychia cooperi

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About Frost-mat Onyx Flower (Achyronychia cooperi) Achyronychia is a monotypic genus of flowering plant containing the single species Achyronychia cooperi, which is known by the common names onyxflower and frost-mat. This plant is native to the Mojave and Sonoran Deserts of northern Mexico and the U. S. states of California, Nevada, Utah and Arizona. In California, it is known from San Diego, Imperial, Riverside, Los Angeles, San Bernardino and Inyo Counties. In Arizona, it occurs in Yuma, Mohave, Pima, Pinal and Maricopa Counties. It has also been reported from Washington County in Utah, and from Clark County, Nevada. Onyxflower is a diminutive plant which lies in a small mat flat on the ground. Its habitat is sand. It radiates several prostrate stems in all directions, each only a few centimeters long. The thick pale green leaves are paddle-shaped and under 2 centimeters long. In the leaf axils grow dense bunches of tiny flowers. There are no petals, but each flower has five thin shiny white sepals that look like tiny fingernails; the genus name Achyronychia is Greek for "chaff fingernail".
Plant Description
Plant Type
Annual herb

Flower Color

Native Status

Natural Setting
Elevation ?
-271' - 5432'

Annual Precip. ?
1.9" - 23.3"

Summer Precip. ?
0.28" - 2.49"

Coldest Month ?
41.9° F - 62.7° F

Hottest Month ?
66.0° F - 90.4° F

Humidity ?
2.64 vpd - 48.25 vpd

Landscaping Information
Nursery Availability
Never or Almost Never Available

Other Names
Common Names

Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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