Montane. Woodlands, openings. Summer.
Horse Creek Trail, August 11, 2009.

Montane. Woodlands, openings. Summer.
East Fork Trail, September 7, 2011 and El Diente Trail, July 31, 2008.

Involucres (the mass of green phyllaries below the actual flower head) are cobwebby hairy.  In the top photograph at left, the glistening hairs are beginning to lengthen in the uppermost very fresh flower.  Four flower buds surround the one open flower and they are still completely enclosed by the phyllaries.  In the second and third photographs at left, you can see the straight, pointed tips of the phyllaries and the numerous, often cob-webby, white hairs.  Under magnification, the straight hairs are seen to be made up of a number of cells with cell walls clearly visible.  The second photograph shows the flower head late in the season after flowers have been pollinated and the seeds have matured.

Montane. Woodlands, openings. Summer.
El Diente Trail, July 31, 2008.

Flowers are most often a yellow/white.  As is true for all Thistles, the flower is composed of a mass of disk flowers; there are no ray flowers surrounding the disk.

Montane. Woodlands, openings. Summer.
East Fork Trail, September 7, 2011.

Basal leaves in shady Spruce forests are quite large,  commonly growing to twelve inches long.  The basal leaves are evident months before the plants flower.

Montane. Woodlands, openings. Summer.
East Fork Trail, September 7, 2011 and
Roaring Fork Road, July 28, 2015.

Leaves vary widely in shape; they can be deeply lobed, moderately lobed, or unlobed and may be flattened or wavy-edged. Spines can be minute or a centimeter long but they are always sharp. Leaves can have a slight winged petiole, but more often are sessile. They also can be clasping or decurrent i.e., continuing down the stem and blending into the stem.

Here is the leaf description from the Flora of North America:

Leaves: blades oblong to lanceolate or oblanceolate, 10–30 × 2–5 cm, margins flat to undulate, spinulose and otherwise entire to coarsely dentate or shallowly to deeply pinnatifid, lobes well separated, spinulose to coarsely few-dentate, main spines slender to stout, 1–15 mm, one or both faces thinly pilose, sometimes thinly arachnoid, green and ± glabrescent at maturity; basal usually absent at flowering, sessile or winged-petiolate; principal cauline well distributed, proximal absent at flowering, moderately reduced distally, winged-petiolate or sessile (proximal), sessile and auriculate-clasping to slightly decurrent 0–2 cm; distal well developed, spreading, lobed or unlobed.

Compare the above with the brief description given by the Flora of Colorado:

Leaves pinnatifid with a broad central midstrip, glabrate above and arachnoid below, 10-30 cm long, not decurrent.

You can see that having a long, detailed description provides you with the many growth forms you might encounter. If you keyed the plant shown on this web page using only the information from Flora of Colorado, you would not get to several specimens of Cirsium parryi shown here. The two descriptions differ considerably:

Leaves "entire to coarsely dentate or shallowly to deeply pinnatifid"  vs. "pinnatifid".
I should also point out that in the Flora of Colorado key to Cirsium it is indicated that the "leaves [are] very shallowly lobed" which is not the same as "pinnatifid".

Leaves: "one or both faces thinly pilose, sometimes thinly arachnoid, green and ± glabrescent at maturity"  vs.  "glabrate above and arachnoid below".

Leaves "sessile and auriculate-clasping to slightly decurrent"  vs.  "not decurrent".

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Cirsium parryi