Biology:Cirsium occidentale
| 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 (Nutt.) Jeps.
| |
| 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]
Description
Cirsium occidentale is a biennial 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] 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]
Varieties
There are several varieties, which differ from each other in range and form:[4]
- Cirsium occidentale var. californicum — California thistle[6]
- Cirsium occidentale var. candidissimum — snowy thistle[7][8]
- Cirsium occidentale var. compactum — compact cobwebby thistle; a short, clumpy California endemic that grows only along the coast of the San Francisco Bay Area and the Central Coast of California[9]
- Cirsium occidentale var. coulteri — Coulter's thistle[10]
- Cirsium occidentale var. lucianum — Cuesta Ridge thistle; a California endemic from the Santa Lucia Range[11]
- Cirsium occidentale var. occidentale — cobwebby thistle[12]
- Cirsium occidentale var. venustum[13][14]
Distribution and habitat
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.
Ecology
It is a larval host to the California crescent, mylitta crescent, and the painted lady butterfly.[17]
Gallery
California thistle
C. occidentale var. compactum blooming
C. occidentale
C. occidentale var. candidissimum
C. occidentale var. candidissimum flower
C. occidentale var. occidentale flower with seed head forming
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References
- ↑ "NatureServe Explorer". NatureServe. 2022. https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.143708.
- ↑ The Plant List, Carduus occidentalis Nutt.
- ↑ Calflora taxon report, University of California, Cirsium occidentale (Nutt.) Jepson, Cobweb Thistle, western thistle
- ↑ 4.0 4.1 4.2 4.3 Jepson Flora Project, ed., "Cirsium occidentale", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=2209
- ↑ 5.0 5.1 5.2 Flora of North America, Western thistle, Cirsium occidentale (Nuttall) Jepson
- ↑ Jepson Flora Project, ed., "Cirsium occidentale var. californicum", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=77401
- ↑ "Plants Profile for Cirsium occidentale candidissimum (snowy thistle)". https://plants.usda.gov/core/profile?symbol=CIOCC.
- ↑ Jepson Flora Project, ed., "Cirsium occidentale var. candidissimum", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=56556
- ↑ Jepson Flora Project, ed., "Cirsium occidentale var. compactum", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=7068
- ↑ Jepson Flora Project, ed., "Cirsium occidentale var. coulteri", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=81843
- ↑ Jepson Flora Project, ed., "Cirsium occidentale var. lucianum", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=81502
- ↑ Jepson Flora Project, ed., "Cirsium occidentale var. occidentale", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=7069
- ↑ "Plants Profile for Cirsium occidentale venustum (cobwebby thistle)". https://plants.usda.gov/core/profile?symbol=CIOCV.
- ↑ Jepson Flora Project, ed., "Cirsium occidentale var. venustum", Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=56557
- ↑ C.Michael Hogan ed. 2010. Cirsium occidentale. Encyclopedia of Life
- ↑ Biota of North America Program 2014 county distribution map
- ↑ The Xerces Society (2016), Gardening for Butterflies: How You Can Attract and Protect Beautiful, Beneficial Insects, Timber Press.
External links
- Jepson Manual treatment — Cirsium occidentale
- Cirsium occidentale — Calphotos Photo gallery, University of California
Wikidata ☰ Q19848754 entry
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