La Graciosa Thistle

Cirsium loncholepis

Description

The La Graciosa thistle is a short-lived perennial herb. The plant is spreading, mound-like or erect and often fleshy and spiny, standing 4-40 in (1-10 dm) in height with one to several stems. Lower leaves are 4-12 in (10-30 cm) long with spiny petioles and deep lobes, usually with secondary lobes or teeth. On the middle and upper leaves, the leaf base forms short, spiny wings along the petiole.

Flower heads are in tight clusters at the tips of stems and are about 0.8-1.6 in (2 -4 cm) wide. Flowers are more or less white with a purplish tube and purple anthers.

This thistle closely resembles the Indian thistle (Cirsium brevistylum ), but can be distinguished by its deeply lobed leaves with secondary lobes. Also, La Graciosa thistle is shorter and does not possess the cobwebby hairs of the Indian thistle.

Habitat

La Graciosa thistle is primarily found in wet soils surrounding dune lakes and in moist dune swales of the California coastal dune ecosystem. Associates in this habitat often include rushes, tules, willows, poison oak, salt grass, and coyote brush. The thistle is largely restricted to these wetland dune habitats with the exception of one disjunct population.

Distribution

Maps show that the wetland habitat area suitable for the La Graciosa thistle no longer exists. There was once a wide distribution of this species, but most wetlands have now been converted for agriculture or other development purposes. As early as 1950, studies were done on the lack of suitable habitat remaining. By 2000, about one-third of the historically occurring populations were gone.

This California endemic has only 17 known locations which occur in southern San Luis Obispo County and northern Santa Barbara County, from the Pismo Dunes lake area and south to the Santa Ynez River. Most occur in the Guadalupe Dune complex.

All populations except one are small and isolated. The one containing a substantial number has a population fluctuating between 6,000 and 54,000 plants. Seven of these populations have reported fewer than 60 plants each. Only one occurs on public land, which is in the Los Padres National Forest.

Threats

Loss of wetland habitat is the greatest threat to the La Graciosa thistle, especially considering that all but one population are found on private lands. One of the destructive uses of the wetland habitats is groundwater pumping. Pumping lowers the water table and dries out wetlands. Petroleum extraction and oil field development for energy, as well as other commercial development also threaten remaining habitat for the thistle.

Other habitat disturbances include grazing and natural events, especially flooding.

The effects of habitat loss have been compounded by the growing number of non-native species that are invading the dune ecosystem. Invasive weeds such as veldt grass, European beach grass, and two varieties of iceplant are serious threats to the natural ecological processes of sandy coastal habitats.

Conservation and Recovery

Recovery and management plans are being created by the U. S. Department of Fish and Wildlife for the La Graciosa thistle. The need for critical habitat designation has been deemed prudent, and will be discussed depending on the magnitude and immediacy of the threats.

The California Exotic Pest Plant Council has taken steps to identify non-native invasive plants that negatively impact the thistle's habitat.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121
http://pacific.fws.gov/

Ventura Fish and Wildlife Office
U. S. Fish and Wildlife Service
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766
Fax: (805) 644-3958

References

United States Department of the Interior. 20 March 2000. "Endangered and Threatened Wildlife and Plants: Final Rule for Endangered Status for Four Plants From South Central Coastal California." Federal Register 65 (54): 14888-14898.

University of California, Berkeley. " Cirsium loncholepis. " CalFlora Database Project: a botanical resource for California on the internet. (http://dlp.cs.berkeley.edu/calflora.) Accessed July 6, 2000.