[3] These are perennial plants that grow from a caudex and fibrous root system.

The stems are erect and unbranched, usually reaching 20 to 60 centimeters (8-24 inches) in height, and taller at times.

The blades vary in shape and are hairy to hairless and generally glandular.

Each head contains up to about 35 disc florets, usually lavender to dark magenta or pinkish purple, sometimes blue.

[5] A number of species contain volatile oils, giving characteristic odors.