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Cirsium rhothophilum
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Surf Thistle
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Cirsium rhothophilum

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About Surf Thistle (Cirsium rhothophilum) Cirsium rhothophilum is a rare North American species of thistle known by the common name surf thistle. It is endemic to California, where it is known only from the coastline around the border between San Luis Obispo and Santa Barbara Counties. It grows in sand dunes and coastal scrub near the beach. Cirsium rhothophilum grows up to 100 cm (39 in) tall with fleshy, woolly herbage usually forming a mound. The thick leaves are wavy and covered in feltlike hairs. They may have smooth, lobed, or toothed edges and small spines. The largest leaves at the base of the plant may reach 25 centimetres (9. 8 inches) in length. The inflorescence bears several clustered flower heads, each head up to 4 centimeters long and 6 cm wide. The heads are lined with woolly phyllaries and filled with off-white to pale yellowish disc florets but no ray florets. The fruit is an achene a few millimeters long with a pappus up to 2 centimeters in length.
Plant Description
Plant Type
Perennial herb

Max. Height
3.3 ft (1 m)

Flower Color
Pink, Purple

Native Status
Natural Setting
Elevation ?
20' - 356'

Annual Precip. ?
13.6" - 16.1"

Summer Precip. ?
0.18" - 0.28"

Coldest Month ?
48.8° F - 51.4° F

Hottest Month ?
62.1° F - 67.8° F

Humidity ?
0.88 vpd - 11.91 vpd

Landscaping Information
Nursery Availability
Never or Almost Never Available

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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