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Plant Profile

La Graciosa Thistle (Cirsium scariosum var. citrinum)

Habitat of Cirsium loncholepis Photo Credit: California Native Plant Society

Global Rank: G1 - Critically Imperiled
Legal Status: Federally Endangered
Family: Asteraceae
State: CA
Nature Serve ID: 156329
Lifeform: Forb/herb
Date Inducted in National Collection:

Description:

La Graciosa thistle is found in coastal wetlands of southwestern San Luis Obispo County and northwestern Santa Barbara County, California. It is named for La Graciosa, a place name provided by Portol in 1769, and near where the original collection was made near what is now the community of Orcutt. Based on historic records, its geographic range remains the same, but fewer than 15 extant populations are believed extant. Many of the known populations are clustered in a few remaining watersheds, including the Santa Maria River and San Antonio Creek in northwestern Santa Barbara County. The average life span is unknown, but some populations are often composed mostly of vegetative plants in different size classes (Teed 2003). Flowers are typically white or tinged with purple and are borne in densely clustered heads (Ferris 1960; Hoover 1970; Keil 2006; Smith 1998). Plants may flower from April to late summer, especially near the coast. It is often mistaken with several other related thistles with preferences for wetland habitats.

Where is La Graciosa Thistle (Cirsium scariosum var. citrinum) located in the wild?

Habitat:

La Graciosa thistle occurs naturally in open sites in wet swales of coastal back dunes, the edges of marshes, and broad river flood plains. It is often associated with such riparian and flood plain species as rushes (Juncus), sedges (Carex), coyote brush (Baccharis pilularis), and arroyo willow (Salix lasiolepis) (Anonymous, 2008a; Hendrickson, 1990).

Distribution:

Southwestern San Luis Obispo County and northwestern Santa Barbara County, California

States & Provinces:

La Graciosa Thistle can be found in California

Which CPC Partners conserve La Graciosa Thistle (Cirsium scariosum var. citrinum)?

Santa Barbara Botanic Garden

Not Sponsored

Conservation Actions

Assigned 06/09/17

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

09/01/2020

Based on an September 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden holds 3 accessions of Cirsium scariosum var. loncholepis in orthodox seed collection. There are as many as 82 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

09/01/2020

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 5 accessions of Cirsium scariosum var. loncholepis in orthodox seed collection. There are as many as 2254 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

08/05/2020

Based on an August 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden has collected 3 seed accessions of Cirsium scariosum var. loncholepis from 2 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass an unknown number of maternal plants

Nature Serve Biotics

05/02/2017

Endemic to coastal wetlands of northern Santa Barbara and southern San Luis Obispo counties, California. Little suitable habitat remains in the area; much has been converted to agriculture and urban development. There are probably fewer than 7 extant occurrences known and the majority are severely threatened by ongoing coastal development, off-road vehicle use of the beach habitat, and other threats. There are no protected populations.

Dieter Wilken

01/01/2010

Loss of wetlands and sporadic inundation of stable wetland habitats. Competition from alien invasives. Trampling by livestock. Expansion of sand dunes, resulting from excessive ORV use. Potential seed predation by thistle head weevil (Rhinocyl

Dieter Wilken

01/01/2010

Among approximately 20 historic occurrences in California, 15 are believed to be extant. With a single exception, only 2-30 plants have been reported at most occurrences, but estimates vary widely based on whether both vegetative and flowering individuals were counted. The notable exception is a population near the mouth of the Santa Maria River in the Guadalupe Dunes Wildlife Refuge, where at least 500 individual plants were observed in 2001 (Anonymous, 2008b).

Dieter Wilken

01/01/2010

Assessment of relationships to and hybridization with similar species, including varieties of elk thistle (Cirsium scariosum).

Dieter Wilken

01/01/2010

A cluster of 5-6 populations in northwestern Santa Barbara County is managed by biologists working for Vandenberg Air Force Base. Populations in the Guadalupe Dunes of San Luis Obispo and Santa Barbara counties are managed by biologists working for California Department of Fish and Game, the US Fish and Wildlife Service, and State Parks and Recreation. Several sites in the Guadalupe Dunes have been provided protection using fences, and one population is the focus of invasive dune grass removal by the San Luis Obispo Conservancy.

Dieter Wilken

01/01/2010

Genetic analyses of extant populations to determine the extent of putative hybridization with and relationships to related species. A better understanding of life history traits and appropriate habitat for sustainable populations.

Dieter Wilken

01/01/2010

Development of a conservation seed bank. Development of a propagation protocol.