Cirsium crassicaule
Encyclopedia
Cirsium crassicaule is a species of thistle
known by the common name slough thistle. It is endemic to the San Joaquin Valley
of California
, where it is known primarily from freshwater
wetland
s.
This native thistle is an annual or biennial herb known to reach three meters in height. The thick stem is hollow and may be nearly 10 centimeters wide at the base. It is coated in hairs and cobwebby fibers. The woolly, webby, spiny leaves are deeply cut into many lobes, the lobes often lined with teeth. The longest leaves near the base of the plant may be 70 centimeters long.
The inflorescence
is a cluster of several flower heads
each up to 3 centimeters long by 3 wide. The head is lined with spiny phyllaries
and filled with pale pink or occasionally white flowers. The fruit is an achene
with a flat, dark brown body about 5 millimeters long and topped with a pappus
which may be 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 slough thistle. It is endemic to the San Joaquin Valley
San Joaquin Valley
The San Joaquin Valley is the area of the Central Valley of California that lies south of the Sacramento – San Joaquin River Delta in Stockton...
of 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 primarily from freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
s.
This native thistle is an annual or biennial herb known to reach three meters in height. The thick stem is hollow and may be nearly 10 centimeters wide at the base. It is coated in hairs and cobwebby fibers. The woolly, webby, spiny leaves are deeply cut into many lobes, the lobes often lined with teeth. The longest leaves near the base of the plant may be 70 centimeters long.
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...
is a cluster of several 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 up to 3 centimeters long by 3 wide. The head is lined with spiny 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 pale pink or occasionally white 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...
with a flat, dark brown body about 5 millimeters long and topped 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...
which may be 2 centimeters in length.