Flora of North America species comparison

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Cirsium occidentale var. compactum

Cirsium occidentale var. lucianum
Photo is of parent taxon

compact cobwebby thistle
Photo is of parent taxon

Cuesta Ridge thistle
Habit Plants compactly branched, forming low rounded mounds, 5–100 cm, densely gray-tomentose. Plants erect, 30–200 cm, densely gray-tomentose.
Leaf

faces gray-tomentose or adaxial ± glabrate.

Involucres

wider than long, 5–8 cm diam., densely arachnoid with fine trichomes connecting tips of adjacent phyllaries.

about as wide as long, 2–4 cm, floccose-arachnoid, without fine trichomes connecting tips of adjacent phyllaries.
Corollas

dark rose-purple, 25–30 mm.

dark reddish purple, 20–24 mm.
Phyllaries

imbricate to subequal, outer and mid apices ± spreading, straight, usually 1–2 cm × usually 1–2 mm.

imbricate, outer ascending to spreading or reflexed, mid apices ascending to spreading, straight or distally curved, usually 5–8 × 1–3 mm.
Heads

borne singly or in ± tight clusters, short-pedunculate, closely subtended and often overtopped by basal and large cauline leaves.

in openly branched arrays, long-pedunculate, elevated well above proximal leaves.
2n

= 30.

Cirsium occidentale var. compactum

Cirsium occidentale var. lucianum
Phenology Flowering winter–summer (Feb–Jul). Flowering spring–summer (Apr–Jul).
Habitat Coastal sea bluffs, dunes in grassland and coastal scrub Chaparral, openings in closed cypress conifer forests, mixed evergreen forests, oak woodlands
Elevation 0–50 m (0–200 ft) 500–1500 m (1600–4900 ft)
Distribution
from FNA
CA
[BONAP county map]
from FNA
CA
[BONAP county map]
Discussion

Variety compactum is locally common along the immediate coast of northern San Luis Obispo County and formerly ranged as far north as San Francisco. Populations referable to this race occur on the California Channel Islands and on the mainland in Monterey County. Because of the very narrow ecologic zone occupied by these plants they are particularly vulnerable to habitat loss. Variety compactum is closely related to vars. occidentale and coulteri.

of conservation concern

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Variety lucianum occupies a narrow corridor along and adjacent to the main ridge of the southern Santa Lucia Mountains of San Luis Obispo County. D. J. Keil and C. E. Turner (1993) treated these plants as an atypical race of var. californicum. They resemble small-headed plants of the latter but differ in their dark, reddish purple corollas. They approach the ranges of var. californicum and var. venustum but are not known to grow with either. They may represent a stabilized emergent form derived by prehistoric hybridization between var. californicum and var. venustum.

of conservation concern

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 19, p. 139. FNA vol. 19, p. 139.
Parent taxa Asteraceae > tribe Cardueae > Cirsium > Cirsium occidentale Asteraceae > tribe Cardueae > Cirsium > Cirsium occidentale
Sibling taxa
C. occidentale var. californicum, C. occidentale var. candidissimum, C. occidentale var. coulteri, C. occidentale var. lucianum, C. occidentale var. occidentale, C. occidentale var. venustum
C. occidentale var. californicum, C. occidentale var. candidissimum, C. occidentale var. compactum, C. occidentale var. coulteri, C. occidentale var. occidentale, C. occidentale var. venustum
Name authority Hoover: Vasc. Pl. San Luis Obispo Co., 310. (1970) D. J. Keil: Sida 21: 214. (2004)
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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