About Cirsium rhothophilum S.F.Blake
Cirsium rhothophilum S.F.Blake, commonly called surf thistle, is a rare thistle species native to North America. This plant is endemic to California, and only occurs along the coastline near the border between San Luis Obispo and Santa Barbara Counties. It grows in beach-adjacent habitats including sand dunes and coastal scrub.
Cirsium rhothophilum can grow up to 100 cm (39 inches) tall. It has fleshy, woolly plant tissue that typically forms a low mound. Its thick leaves are wavy, covered in felt-like hairs, and bear small spines; leaf edges may be smooth, lobed, or toothed. The largest basal leaves can reach 25 centimeters (9.8 inches) in length.
The inflorescence holds several clustered flower heads. Each flower head can grow up to 4 centimeters long and 6 centimeters wide. Flower heads are lined with woolly phyllaries, and filled with off-white to pale yellowish disc florets; they do not produce ray florets. The fruit is a small achene a few millimeters long, topped with a pappus that can reach up to 2 centimeters in length.
