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Arnica sororia
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Soro Arnica
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Arnica sororia

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About Soro Arnica (Arnica sororia) Arnica sororia is a species of arnica known by the common name twin arnica. It is native to western North America from British Columbia to California to Nebraska, where it grows in many types of habitat. It is a rhizomatous perennial herb producing one or more hairy, hairy stems 10 to 50 centimeters tall. There are several pairs of broadly lance-shaped leaves along along the stem, the lower ones borne on petioles. Leaves may reach up to 14 centimeters long. The flower cluster holds one to five daisylike flower heads lined with phyllaries coated in hairy hairs. The flower head has a center of hairy yellow disc florets and a fringe of yellow ray florets. The fruit is an achene a few millimeters long with a white pappus.
Plant Description
Plant Type
Perennial herb

Max. Height
0.33 - 1.6 ft (0.1 - 0.49 m)

Flower Color

Native Status

Natural Setting
Site Type
Open places


Elevation ?
1708' - 10636'

Annual Precip. ?
14.2" - 40.5"

Summer Precip. ?
0.85" - 2.26"

Coldest Month ?
24.6° F - 34.8° F

Hottest Month ?
46.0° F - 63.0° F

Humidity ?
0.56 vpd - 17.58 vpd

Landscaping Information
Nursery Availability
Never or Almost Never Available

Other Names
Common Names
Twin Arnica

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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