Flora of North America species comparison

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Cirsium occidentale var. occidentale
Photo is of parent taxon

cobweb thistle, cobwebby thistle
Habit Plants erect, usually 30–150 cm or taller.
Leaf

faces usually densely tomentose abaxially, less so and sometimes glabrate adaxially.
Involucres

usually wider than long, 4–5 cm diam., ± densely and persistently arachnoid with fine trichomes connecting tips of adjacent phyllaries.
Corollas

± bright purple, usually 25–35 mm.
Phyllaries

usually ± imbricate, outer ascending or spreading or reflexed, mid phyllary apices ascending to spreading, straight or distally curved, usually 1–2 cm × 1–2 mm.
Heads

usually long- pedunculate, sometimes in tight clusters at ends of peduncles, elevated well above proximal leaves.
2n

= 28, 29, 30.

Cirsium occidentale var. occidentale
Phenology Flowering spring–summer (Mar–Jul).
Habitat Coastal scrub, chaparral, oak woodlands, stabilized dunes, roadsides
Elevation 0–200 m (0–700 ft)
Distribution
from FNA
CA
[BONAP county map]
Discussion

Variety occidentale occupies a variety of habitats in the coastal zone of southern and central California. Considerable variation occurs from population to population in head size, flower color, and pubescence. It sometimes occurs together with and appears to intergrade with var. coulteri. Where there has been no hybridization, the two may be strikingly dissimilar, but individuals of some populations cannot be assigned with confidence to either variety.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 19, p. 137.
Parent taxa Asteraceae > tribe Cardueae > Cirsium > Cirsium occidentale
Sibling taxa
C. occidentale var. californicum, C. occidentale var. candidissimum, C. occidentale var. compactum, C. occidentale var. coulteri, C. occidentale var. lucianum, C. occidentale var. venustum
Name authority unknown
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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