| Cirsium occidentale | |
|---|---|
 | |
| Flower head of Cirsium occidentale | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Asterales |
| Family: | Asteraceae |
| Genus: | Cirsium |
| Species: | C. occidentale |
| Binomial name | |
| Cirsium occidentale | |
| Synonyms [2] | |
Cirsium coulteri | |
Cirsium occidentale, with the common name cobweb thistle or cobwebby thistle, is a North American species of thistle in the family Asteraceae. [3]
Cirsium occidentale is a biennial plant or perennial plant forming a taproot. It may be short or quite tall, forming low clumps or towering to heights approaching 3 meters (10 feet). The leaves are dull gray-green to bright white due to a coating of hairs, and the most basal ones on large plants may be nearly 0.5 m (1+1⁄2 ft) in length. [4] [3] The petioles are winged and spiny and the leaves are toothed or edged with triangular lobes. [5]
The inflorescence at the top of the whitish stem holds one to several flower heads. Each head is sphere-like, covered in large phyllaries with very long, spreading spines which are laced, often quite heavily, in fibers resembling cobwebs. [5]
The head is packed with disc florets which may be white to blood red to shades of purple. The largest flower heads exceed 8 centimeters (3 inches) in diameter. [4] The heads do not open in synchrony, perhaps allowing greater likelihood of being pollinated. [5]
There are several varieties, which differ from each other in range and form: [4]
The plant is widespread and fairly common across most of California: in its mountain ranges, valleys, and the Mojave Desert; and in the western Great Basin region in western Nevada, southern Oregon, and southwestern Idaho. [15] [4] [16]
Unlike many introduced thistles, this native species is not a troublesome weed.
It is a larval host to the California crescent, mylitta crescent, and the painted lady butterfly. [17]
Cirsium is a genus of perennial and biennial flowering plants in the Asteraceae, one of several genera known commonly as thistles. They are more precisely known as plume thistles. These differ from other thistle genera in having feathered hairs to their achenes. The other genera have a pappus of simple unbranched hairs.
Cirsium quercetorum is a species of thistle endemic to coastal California, its common names include brownie thistle and Alameda thistle.
Cirsium arizonicum, the Arizona thistle, is a North American species of thistle in the family Asteraceae, native to the southwestern United States and northwestern Mexico. It has been found in Arizona, southeastern California, New Mexico, Nevada, Colorado, Utah, Sonora, and northwestern Chihuahua.
Cirsium neomexicanum is a North American species of thistle known by the common names New Mexico thistle, powderpuff thistle, lavender thistle, foss thistle and desert thistle.
Sambucus racemosa is a species of elderberry known by the common names red elderberry and red-berried elder.
Blitum californicum is a species of flowering plant in the amaranth family known by the common names California goosefoot and (ambiguously) "Indian lettuce".
Chaenactis douglasii is a North American species of flowering plant in the daisy family known by the common name Douglas' dustymaiden.
Chaenactis glabriuscula, with the common name yellow pincushion, is a species of flowering plant in the daisy family. It is native to California and Baja California.
Chrysothamnus viscidiflorus is an American species of shrub in the family Asteraceae known by the common names yellow rabbitbrush and green rabbitbrush.
Cirsium andrewsii is an uncommon species of thistle known by the common name Franciscan thistle. It is endemic to California, where it is known from the coastline of the San Francisco Bay Area from Marin to San Mateo Counties. There are also reports of isolated populations in the Klamath Mountains and in the Sierra Nevada.
Cirsium brevistylum is a species of thistle known by the common names Indian thistle and clustered thistle. It is native to western North America having been found in southwestern British Columbia, Washington, Oregon, Idaho, Montana, and California.
Cirsium ciliolatum is a species of thistle known by the common name Ashland thistle. It is endemic to the Klamath Mountains, where it is known from only a few occurrences in Jackson and Josephine Counties in Oregon, as well as neighboring Humboldt and Siskiyou Counties in California. It is related to Cirsium undulatum and may be more accurately described as a variety of that species.
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 wetlands. It has been found in only a few locations in Kern, Kings, and San Joaquin Counties.
Cirsium cymosum is a North American species of thistle known by the common name peregrine thistle. It is native to the western United States, where it has been found in California, Oregon, Nevada, Utah, Idaho, Wyoming, and Montana.
Cirsium douglasii is a species of thistle known by the common names Douglas' thistle and California swamp thistle.
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 boggy habitats.
Cirsium ochrocentrum is a species of thistle known by the common name yellowspine thistle. It is native to the Great Plains of the Central United States and to the desert regions of the western United States and northern Mexico. Its range extends from eastern Oregon east to the Black Hills of South Dakota, south as far as the Mexican State of Durango.
Cirsium rhothophilum is a rare North American 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.
Cirsium scariosum is a species of thistle known by the common names meadow thistle, elk thistle and dwarf thistle. It is native to much of western North America from Alberta and British Columbia, south to Baja California. There are also isolated populations on the Canadian Atlantic Coast, on the Mingan Archipelago in Québec, where it is called the Mingan thistle.
Paracantha gentilis is a species of tephritid or fruit fly in the genus Paracantha of the family Tephritidae. It has a widespread distribution throughout the Western United States, and has also been found as far south as Mexico and Costa Rica. It most closely resembles Paracantha culta, which is widespread in the Southeastern United States, but P. gentilis can be distinguished by having smaller spots on the head.
Media related to Cirsium occidentale at Wikimedia Commons
