Cirsium rhothophilum
Encyclopedia
Cirsium rhothophilum is a species of thistle
known by the common name surf thistle. It is endemic to California
, where it is known only from the coastline around the border between San Luis Obispo
and Santa Barbara Counties
. It grows in sand dunes
and coastal scrub near the beach. This native thistle grows up to a meter tall with fleshy, woolly herbage usually forming a mound. The thick leaves are wavy and covered in feltlike hairs. They may have smooth, lobed, or toothed edges and small spines. The largest leaves at the base of the plant may reach 25 centimeters. The inflorescence
bears several clustered flower heads
, each head up to 4 centimeters long and 6 wide. The heads are lined with woolly phyllaries
and filled with off-white to pale yellowish flowers. The fruit is an achene
a few millimeters long with a pappus
up to 2 centimeters in length.
Cirsium
Cirsium is a genus of perennial and biennial flowering plants in the Asteraceae, one of several genera known commonly as thistles. They are more accurately known as Plume thistles. These differ from other thistle genera in having feathered hairs to their achenes...
known by the common name surf thistle. It is endemic to California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, where it is known only from the coastline around the border between San Luis Obispo
San Luis Obispo County, California
San Luis Obispo County is a county located along the Pacific Ocean in the Central Coast of the U.S. state of California, between Los Angeles and the San Francisco Bay Area. As of the 2010 census its population was 269,637, up from 246,681 at the 2000 census...
and Santa Barbara Counties
Santa Barbara County, California
Santa Barbara County is a county located in the southern portion of the U.S. state of California, on the Pacific coast. As of 2010 the county had a population of 423,895. The county seat is Santa Barbara and the largest city is Santa Maria.-History:...
. It grows in sand dunes
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
and coastal scrub near the beach. This native thistle grows up to a meter tall with fleshy, woolly herbage usually forming a mound. The thick leaves are wavy and covered in feltlike hairs. They may have smooth, lobed, or toothed edges and small spines. The largest leaves at the base of the plant may reach 25 centimeters. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
bears several clustered flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
, each head up to 4 centimeters long and 6 wide. The heads are lined with woolly phyllaries
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
and filled with off-white to pale yellowish flowers. The fruit is an achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
a few millimeters long with a pappus
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
up to 2 centimeters in length.