All thistles are prickly, but cirsium eatonii
especially so, particularly towards the tip of the stems, where the flower heads, involucral bracts and uppermost leaves all combine to create a large spiny cluster. The colorful component is the dense cluster of tubular, lavender pink disc florets, usually pointing upwards; beneath is a cup-shaped involucre, green in color, bearing a regular array of purplish bracts (phyllaries), both hairy and spiny. The styles of the flowers have a slightly lighter shade of pink, and project well beyond the end of the tubes.
The plant stem is thick and rigid, single or lightly branched, with long, thin leaves growing mostly around the base. There are eight varieties of Eaton's thistle, differing in the size and color of the flowers, the hairiness of the phyllaries and the dimensions of the corollas.