Cirsium hydrophilum
Encyclopedia
Cirsium hydrophilum is a species of thistle
which is endemic to California
, where it is found only in the San Francisco Bay Area
and the Sacramento-San Joaquin River Delta. This native thistle grows in wet bog
gy habitats.
.
The inflorescence
bears one or more flower heads
, each up to 3 centimetres (1.2 in) long. The head is lined with sticky, twisted, spiny phyllaries
and contains pink to purple flowers. The fruit is an achene
a 2–4 mm (0.078740157480315–0.15748031496063 in) long topped with a pappus
of about 1.5 centimetre (0.590551181102362 in) centimeters.
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...
which 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 found only in the San Francisco Bay Area
San Francisco Bay Area
The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...
and the Sacramento-San Joaquin River Delta. This native thistle grows in wet bog
Bog
A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....
gy habitats.
Description
The Cirsium hydrophilum thistle may reach 2 metres (6.6 ft) in height with a branching, cobwebby stem. The leaves are longest near the base of the plant, approaching 90 centimetres (35.4 in) in length. They are cut into toothed lobes and covered in spines, particularly along the petiolePetiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
.
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 one or more 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 centimetres (1.2 in) long. The head is lined with sticky, twisted, 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 contains pink to purple 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 2–4 mm (0.078740157480315–0.15748031496063 in) long 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...
of about 1.5 centimetre (0.590551181102362 in) centimeters.
Varieties
There are two very localized varieties:- The rare Cirsium hydrophilum var. hydrophilum, the Suisun thistle, is known from two occurrences in the Suisun MarshSuisun MarshLocated in northern California the Suisun Marsh is the largest brackish marsh on west coast of the United States of America. The marsh land is part of the San Francisco Bay tidal estuary, and subject to tidal ebb and flood...
, in the salt marshSalt marshA salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh...
habitat of the Delta. It is treated as a federally listed endangered speciesEndangered speciesAn endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
. - The very rare Cirsium hydrophilum var. vaseyi, Mt. Tamalpais thistle or Vasey's thistle, is known from about twenty occurrences on Mount TamalpaisMount TamalpaisMount Tamalpais is a peak in Marin County, California, United States, often considered symbolic of Marin County. Much of Mount Tamalpais is protected within public lands such as Mount Tamalpais State Park and the Mount Tamalpais Watershed.-Geography:...
in Marin CountyMarin County, CaliforniaMarin County is a county located in the North San Francisco Bay Area of the U.S. state of California, across the Golden Gate Bridge from San Francisco. As of 2010, the population was 252,409. The county seat is San Rafael and the largest employer is the county government. Marin County is well...
, in water seeps on the serpentine soilSerpentine soilA serpentine soil is derived from ultramafic rocks, in particular serpentinite, a rock formed by the hydration and metamorphic transformation of ultramafic rock from the Earth's mantle....
s of the mountain. It is currently not a listed federal or state endangered species.