A common perennial of dry prairies with slender, erect stems, growing about 2 feet tall, often in patches. Leaves are pinnately compound with narrow leaflets less than 1 inch long and 1/8 inch wide that are dotted beneath. Elongated heads of purple flowers, about ¼ inch long, top the stems. The flowers at the bottom of the spike bloom first, forming a wreath that climbs the spike as blooming progresses.