Rigiopappus is a genus of North American plants in the aster tribe within the sunflower family. It is closely related to genus Pentachaeta. Species The only known species is Rigiopappus leptocladus, sometimes known as wireweed. It is an annual plant sending up slender stems terminating in small daisylike yellow flowers. It is native to the western United States (California, Nevada, Oregon, Washington, Idaho).