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Clokey Thistle (Cirsium clokeyi)
Perennial Forbs Around Las Vegas, Vegetation Around Las Vegas
Whitespine Thistle (Cirsium clokeyi)

General: Clokey Thistle (Cirsium clokeyi) is a two-year or short-lived perennial that spends the first year as a rosette of spiky leaves. In the second year, it sends up a flower stalk with spiky leaves topped with spike-protected purplish flowerheads. The spines are unusually long for thistles, white, and the underside of the leaves lack wooly hairs.

Around Las Vegas, Clokey Thistle is an uncommon component of montane vegetation communities in moist and dry, well-drained areas in the Canadian Life (Pine-Fir Forest), Hudsonian (Bristlecone Pine Forest), and Alpine (Alpine Tundra) life zones. Look for this species up on Mt. Charleston, in particular, on the upper slopes and summit of Griffith Peak.

This is a rare plant with only some 10,000 individuals living in a area about 8-miles in diameter. Please be careful around these plants and don't pick the flowers!

Compare this species with Arizona Thistle, which (1) has shorter spines protecting the flowerhead and leaves, and (2) has wooly hairs on the underside of the leaves.

Whitespine Thistle (Cirsium clokeyi)

Family: Sunflower (Asteraceae).

Other Names: Whitespine Thistle

Plant Form: Basal rosette, then upright stalks topped with flowerheads

Height: To about 6 feet, shorter at higher elevations.

Whitespine Thistle (Cirsium clokeyi)

Stems: Usually a single main stem that branches above to a few stems.

Leaves: Basal leaves long and narrow with spine-covered lobes; spines whitish, long. Upper leaves few, smaller, spiny. Main spines on leaves to 1 inch. Leaves without wooly hairs (not tomentose; glabrous).

Flowers: Blooms during summer. Inflorescence: flowerhead formed of many flowers subtended by spiny bracts. Flowers emerge from a round, spiky ball (involucre) that gets to about 1-inch diameter and has whitish spines to 1-inch long (at least as long as the flowers). Flowers light purplish.

Seeds: achene.

Whitespine Thistle (Cirsium clokeyi)

Habitat: Moist as well as dry, rocky, well-drained gravelly areas in the desert mountains. Mountains tops, ridges, avalanche chutes.

Elevation: About 7,000 to 12,000 feet.

Distribution: Endemic to Clark County, Nevada. This species occurs only in the Spring Mountains from the Griffith Peak area to the head of Lee Canyon.

Comments: The seeds of thistles are a favorite for American Goldfinches and Lesser Goldfinches, who usually delay breeding until the seeds are ready to eat.

Note: All distances, elevations, and other facts are approximate. Names generally follow the USDA database.
copyright; Last updated 081227

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