Mule ear (Wyethia amplexicaulis) , also known as green dock and black sunflower, is a tufted perennial with smooth waxy leaves and a thick woody taproot. It reproduces only by seed, yet it is aggressive, and once it becomes established it is highly competitive.
Cattle seldom eat mule ear when other forage is available; however, sheep eat the heads when in full bloom and occasionally consume a small quantity of the young leaves before they completely unfold. Since mule ear is relatively unpalatable, it increases in density with continued heavy use of the range and in some cases has increased almost to the exclusion of other species.
Rehabilitation of mule-ear-infested ranges through protection requires many years and such a procedure seems to be economically impractical. It would be highly desirable if a more expedient and practical method could be found for rehabilitating infested ranges.
Tingey, D. C. and Cook, C. Wayne, "Bulletin No. 375 - Eradication of Mule Ear with Herbicides and Its Relation to Production of Forage on Range Lands" (1955). UAES Bulletins. Paper 337.