Cirsium occidentale
{{Short description|Species of thistle}}
{{Speciesbox
|image = Cirsium_occidentale.jpg
|image_caption = Flower head of Cirsium occidentale
|status = G3
|status_system = TNC
|genus = Cirsium
|species = occidentale
|synonyms_ref = [http://www.theplantlist.org/tpl1.1/search?q=Cirsium+occidentale The Plant List, Carduus occidentalis Nutt.]
|synonyms = Cirsium coulteri
}}
Cirsium occidentale, with the common name cobweb thistle or cobwebby thistle, is a North American species of thistle in the family Asteraceae.{{cite web |title=Cirsium occidentale Calflora |url=https://www.calflora.org/app/taxon?crn=2139 |website=www.calflora.org |access-date=17 May 2024}}
Description
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 {{convert|3|m|ft|abbr=off|sp=us|frac=2}}. 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 {{convert|0.5|m|ft|abbr=on|sp=us|frac=2}} in length.{{Jepson eFlora|2209|Cirsium occidentale}} The petioles are winged and spiny and the leaves are toothed or edged with triangular lobes.
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.
The head is packed with disc florets which may be white to blood red to shades of purple. The largest flower heads exceed {{convert|8|cm|in|abbr=off|sp=us|frac=2}} in diameter. The heads do not open in synchrony, perhaps allowing greater likelihood of being pollinated.[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250066386 Flora of North America, Western thistle, Cirsium occidentale (Nuttall) Jepson]
Varieties
There are several varieties, which differ from each other in range and form:
- Cirsium occidentale var. californicum — California thistle{{Jepson eFlora|77401|Cirsium occidentale var. californicum}}
- Cirsium occidentale var. candidissimum — snowy thistle{{Cite web |title=Plants Profile for Cirsium occidentale candidissimum (snowy thistle) |url=https://plants.usda.gov/core/profile?symbol=CIOCC |access-date=2019-02-18 |website=plants.usda.gov}}{{Jepson eFlora|56556|Cirsium occidentale var. candidissimum}}
- 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{{Jepson eFlora|7068|Cirsium occidentale var. compactum}}
- Cirsium occidentale var. coulteri — Coulter's thistle{{Jepson eFlora|81843|Cirsium occidentale var. coulteri}}
- Cirsium occidentale var. lucianum — Cuesta Ridge thistle; a California endemic from the Santa Lucia Range{{Jepson eFlora|81502|Cirsium occidentale var. lucianum}}
- Cirsium occidentale var. occidentale — cobwebby thistle{{Jepson eFlora|7069|Cirsium occidentale var. occidentale}}
- Cirsium occidentale var. venustum{{Cite web |title=Plants Profile for Cirsium occidentale venustum (cobwebby thistle) |url=https://plants.usda.gov/core/profile?symbol=CIOCV |access-date=2019-02-18 |website=plants.usda.gov}}{{Jepson eFlora|56557|Cirsium occidentale var. venustum}}
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.C.Michael Hogan ed. 2010. [http://www.eol.org/pages/468309 Cirsium occidentale. Encyclopedia of Life][http://bonap.net/MapGallery/County/Cirsium%20occidentale.png Biota of North America Program 2014 county distribution map]
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.The Xerces Society (2016), Gardening for Butterflies: How You Can Attract and Protect Beautiful, Beneficial Insects, Timber Press.
Gallery
Asteraceae cirsium occidentale California Thistle.jpg|California thistle
Cirsium occidentale var. compactum.jpg|C. occidentale var. compactum blooming
Cirsium occidentale plant.jpg|C. occidentale
Cirsium occidentale candidissimum (5378322408).jpg|C. occidentale var. candidissimum
Cirsium occidentale candidissimum (5378323652).jpg|C. occidentale var. candidissimum flower
Cirsium occidentale v. occidentale.jpg|C. occidentale var. occidentale flower with seed head forming
References
{{Reflist}}
External links
- [http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=2209 Jepson Manual treatment — Cirsium occidentale]
- [http://calphotos.berkeley.edu/cgi/img_query?query_src=photos_index&where-taxon=Cirsium+occidentale Cirsium occidentale — Calphotos Photo gallery, University of California]
- {{Commons category-inline|Cirsium occidentale}}
{{Taxonbar|from=Q19848754}}
Category:Flora of the Western United States
Category:Natural history of the California chaparral and woodlands
Category:Natural history of the California Coast Ranges
Category:Natural history of the Mojave Desert
Category:Natural history of the Peninsular Ranges
Category:Natural history of the San Francisco Bay Area
Category:Natural history of the Santa Monica Mountains
Category:Natural history of the Transverse Ranges
Category:Plants described in 1901