Cirsium occidentale

Cirsium occidentale
Cirsium occidentale
Cobwebby thistle
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Tribe: Cynareae
Genus: Cirsium
Species: C. occidentale
Binomial name
Cirsium occidentale
(Nutt.) Jeps.

Cirsium occidentale, with the common name Cobwebby thistle, is a species of thistle native throughout California deserts, mountains, and valleys, and in western Nevada, southern Oregon, and southwestern Idaho. [1] [2] Unlike many introduced exotic thistles, this native species is not a troublesome weed.

Description

Cirsium occidentale may be short or quite tall, forming low clumps or towering to heights approaching 3 metres (9.8 ft). 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 .5 metres (1.6 ft) in length.[2] 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 somewhat spherical, 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 8 centimetres (3.1 in) in diameter. [2]

Varieties

There are several varieties which differ from each other. [3] For example Cirsium occidentale var. compactum the compact cobwebby thistle, is a short, clumpy plant which grows only along the coast of the San Francisco Bay Area and Central Coast of California region. [4]

Flower head of Cirsium occidentale, the Cobwebby thistle.
File:ThistleCobweb.jpg
Flower head of Cirsium occidentale, the Cobwebby thistle.

References

  1. ^ C.Michael Hogan ed. 2010. Cirsium occidentale. Encyclopedia of Life
  2. ^ a b c U.C. Jepson; C. occidentale; 1993; accessed 3.20.2011
  3. ^ U.C. Jepson; C. occidentale 8 varieties list/treatment links; 1993; accessed 3.20.2011
  4. ^ U.C. Jepson; C. occidentale var. compactum; 1993; accessed 3.20.2011


External links


Stub icon This Cynareae article is a stub. You can help Wikipedia by expanding it.