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Suisun Thistle
Cirsium hydrophilum
About Suisun Thistle (Cirsium hydrophilum) 0 Nurseries Carry This Plant Cirsium hydrophilum is a species of thistle which is endemic to California, where it is found only in the San Francisco Bay Area and the Sacramento-San Joaquin River Delta. This native thistle grows in wet boggy habitats. Cirsium hydrophilum may reach 2 metres (6. 6 ft) in height with a branching, cobwebby stem. The leaves are longest near the base of the plant, approaching 90 centimetres (35 in) in length. They are cut into toothed lobes and covered in spines, particularly along the petiole. The inflorescence bears one or more flower heads, each up to 3 centimetres (1. 2 in) long. The head is lined with sticky, twisted, spiny phyllaries and contains pink to purple flowers. The fruit is an achene a 2-4 millimetres (0. 079-0. 157 in) long topped with a pappus of about 1. 5 centimetres (0. 59 in) centimeters. Varieties: There are two very localized varieties:The rare Cirsium hydrophilum var. hydrophilum, the Suisun thistle, is known from two occurrences in the Suisun Marsh, in the salt marsh habitat of the Delta in Solano County. It is treated as a federally listed endangered species. The very rare Cirsium hydrophilum var. vaseyi, Mt. Tamalpais thistle or Vasey's thistle, is known from about twenty occurrences on Mount Tamalpais in Marin County, in Vacaville, California in Solano County, and inside the Presidio in the City of San Francisco. It is currently not a listed federal or state endangered species.
Plant Description
Plant Type
Plant Type
Perennial herb

6.6 ft tall

Flower Color
Flower Color
Pink, Purple

Wildlife Supported

Landscaping Information
Natural Setting
Annual Precipitation: 19.8" - 64.4", Summer Precipitation: 0.23" - 0.46", Coldest Month: 46.7" - 50.9", Hottest Month: 62.7" - 72.5", Humidity: 1.37" - 18.29", Elevation: 4" - 2553"

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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