Prairie dock belongs to the Aster (Asteraceae) family and has clusters of large, sandpapery, spade-shaped basal leaves up to 16 inches long. The flower heads are in an open cluster at the top of a smooth, shiny, nearly leafless 2 to 10 foot tall stalk. Each individually stalked flower head is 2 to 3 inches wide with several broad, shiny, green, rounded bracts and 12 to 25 yellow, petal-like ray flowers with notched tips surrounding yellow disk flowers. Prairie dock is drought-resistant and is a long-lived perennial with a fragrant, resinous sap. Prairie dock blooms summer to fall and is found in deep-soil and loamy prairies in the eastern half of the tallgrass region, but rare or absent from western Missouri westward. Prairie dock is among the tallest and largest-leaved of the prairie plants. In open prairies, the leaves of Prairie dock often orient themselves along a north-south axis to minimize heat load.