(Cirsium rhothophilum)
| Family |
Asteraceae (Sunflowers) |
| Life History |
Perennial |
| Listing |
California Threatened |
| Range |
San Luis Obispo and Santa Barbara Counties |
| CDFW Region |
South Coast (Region 5) |
Background
CC photo by Spencer Riffle.
Cirsium rhothophilum. CDFW illustration by Mary Ann Showers. (Click to enlarge)
Surf thistle (Cirsium rhothophilum) is a California threatened plant species, which means that killing or possessing the plant is prohibited by the California Endangered Species Act (CESA). Surf thistle is a perennial plant in the sunflower family (Asteraceae) and is restricted to unstable sand dunes. It is most often found on the sheltered sides of dunes where sand is accumulating. Surf thistle’s leaves form large rosettes and are deeply wavy, succulent, and covered in dense white or grey hairs that protect the plant from high sun exposure. The branches grow low to the ground, and each can have several bell-shaped flowering heads with flower color ranging from white to light yellow. Surf thistle is monocarpic, meaning it typically flowers and sets seed once in its lifetime.
Distribution
Surf thistle only occurs on the coastline from southern San Luis Obispo County to northern Santa Barbara County. The California Natural Diversity Database lists 21 total occurrences, and of those 19 are presumed extant. Several surf thistle occurrences have very small populations (fewer than 20 plants), but three populations have had over 1000 plants. Many occurrences have not been surveyed in decades. Most occurrences are on protected land, managed by entities such as the U.S. Fish and Wildlife Service, Vandenberg Space Force Base, and the Nature Conservancy.
Conservation
Threats to surf thistle include off-road vehicle use, sea level rise due to climate change, and competition from invasive plants including iceplant (Carpobrotus spp.) and European beachgrass (Ammophila arenaria). Known occurrences should be surveyed and monitored to better understand population dynamics, species needs, and threats to the species. Actions that would benefit the species include careful removal of non-native plants, prevention of off-road vehicles from accessing sensitive habitat, and public education to increase awareness of fragile dune ecosystems.
CDFW may issue permits for surf thistle pursuant to CESA, and we invite you to learn more about the California laws protecting surf thistle and other California native plants. Populations of surf thistle occur in CDFW’s South Coast Region.
Updated 8/7/2025