Cirsium occidentale var. compactum

Hoover

Vasc. Pl. San Luis Obispo Co., 310. 1970.

Common names: Compact cobwebby thistle
EndemicConservation concern
Treatment appears in FNA Volume 19. Treatment on page 139. Mentioned on page 137.

Plants compactly branched, forming low rounded mounds, 5–100 cm, densely gray-tomentose. Leaf faces gray-tomentose or adaxial ± glabrate. Heads borne singly or in ± tight clusters, short-pedunculate, closely subtended and often overtopped by basal and large cauline leaves. Involucres wider than long, 5–8 cm diam., densely arachnoid with fine trichomes connecting tips of adjacent phyllaries. Phyllaries: imbricate to subequal, outer and mid apices ± spreading, straight, usually 1–2 cm × usually 1–2 mm. Corollas dark rose-purple, 25–30 mm. 2n = 30.


Phenology: Flowering winter–summer (Feb–Jul).
Habitat: Coastal sea bluffs, dunes in grassland and coastal scrub
Elevation: 0–50 m

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

Selected References

None.

Lower Taxa

None.
David J. Keil +
Hoover +
Carduus occidentalis +
Compact cobwebby thistle +
0–50 m +
Coastal sea bluffs, dunes in grassland and coastal scrub +
Flowering winter–summer (Feb–Jul). +
Vasc. Pl. San Luis Obispo Co., +
Endemic +  and Conservation concern +
Compositae +
Cirsium occidentale var. compactum +
Cirsium occidentale +
variety +