Southwest Colorado Wildflowers, Cirsium calcareum

There are over a dozen Thistles, native and introduced, in the Four Corners. Some of these Thistles reproduce from rhizomes; others are biennial, reproducing from seeds. All are spiny and have only disk flowers. Most Thistles are large and obvious in plant and in flower. Some are serious invaders of meadows and pastures.

The genus name, "Cirsium", is Greek for "dilated vein" from the bygone belief that a Thistle distillate opens clogged veins.

Cirsium calcareum (Thistle)
Asteraceae (Sunflower Family)

Foothills, montane. Woodlands, openings. Spring, summer.
Navajo Reservation near Teec Nos Pos, Arizona, June 24, 2006.

This compact, short thistle is a fortress of spines with a cylindrical flower head emerging from a pineapple-like bud. The pineapple appearance is due to the phyllaries, the whorl of triangular, overlapping bracts subtending the flower head. The plant grows in low Pinyon-Juniper forests, often in rocky areas.

The genus was named by Phillip Miller (1691-1771). The species was at first named Cnicus drummondii by Alice Eastwood in 1893 from a specimen she collected near present day Mesa Verde National Park. It was renamed Cnicus calcareus by Marcus Jones in 1895 and then Cirsium calcareum in 1915 by Elmer Wooton (1865-1945) and Paul Standley (1884-1963).

"Calcareum", Latin for "spur" or "limestone", could refer to a spur on the Thistle or to calcareous soil conditions.

Cirsium calcareum (Thistle)
Asteraceae (Sunflower Family)

Foothills, montane. Woodlands, openings. Spring, summer.
Navajo Reservation near Teec Nos Pos, Arizona, June 24, 2006.

Cirsium calcareum (Thistle)
Asteraceae (Sunflower Family)

Foothills, montane. Woodlands, openings. Spring, summer.
Navajo Reservation near Teec Nos Pos, Arizona, June 24, 2006.