Flora of North America species comparison

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Cirsium occidentale var. compactum

Cirsium occidentale var. venustum
Photo is of parent taxon

compact cobwebby thistle
Photo is of parent taxon

cobwebby thistle, Venus thistle
Habit Plants compactly branched, forming low rounded mounds, 5–100 cm, densely gray-tomentose. Plants usually erect, usually 50–300 cm, variably tomentose, sometimes ± glabrate.
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.

usually longer than wide, 2–6 cm, subglabrous to densely arachnoid, usually without fine trichomes connecting tips of adjacent phyllaries.
Corollas

dark rose-purple, 25–30 mm.

usually ± red (white, pink, rarely purple), 23–35 mm.
Phyllaries

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

imbricate, outer and mid apices ascending to rigidly spreading or reflexed, straight, 5–20+ × usually 2–3 mm.
Heads

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

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

= 30.

= 30.

Cirsium occidentale var. compactum

Cirsium occidentale var. venustum
Phenology Flowering winter–summer (Feb–Jul). Flowering spring–summer (Apr–Jul).
Habitat Coastal sea bluffs, dunes in grassland and coastal scrub Foothill oak-pine woodlands, grasslands, chaparral, pinyon-juniper woodlands, Joshua tree woodlands, roadsides
Elevation 0–50 m (0–200 ft) 200–2300 m (700–7500 ft)
Distribution
from FNA
CA
[BONAP county map]
from FNA
CA; NV
[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 venustum has the widest ecological range of the races of C. occidentale. Populations occur within a few miles of the California coast in the North and South Coast Ranges and western Transverse Range and range eastward across the state into scattered sites in the Sierra Nevada to the higher elevations of the arid mountains of the western Mojave Desert and adjacent areas of the southwestern Great Basin Desert. Most populations of these plants can be recognized by their striking red to reddish pink corollas. The heads are sometimes visited by hummingbirds as well as by a variety of insects. Intermediates have been documented between var. venustum and vars. californicum and candidissimum.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 19, p. 139. FNA vol. 19, p. 140.
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. lucianum, C. occidentale var. occidentale
Synonyms Carduus venustus, C. occidentale subsp. venustum, C. proteanum
Name authority Hoover: Vasc. Pl. San Luis Obispo Co., 310. (1970) (Greene) Jepson: Man. Fl. Pl. Calif., 1167. (1925)
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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