Hymenoxys odorata is a species of flowering plant in the daisy family known by the common names bitter rubberweed and western bitterweed. It is native to the southwestern and south-central United States from southern California to Texas north as far as Kansas and Colorado, as well as northern Mexico (Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, Sonora, Tamaulipas). It grows in dry regions.Biota of North America Program 2014 county distribution mapCalflora taxon report, University of California, Hymenoxys odorata DC., bitter rubberweed, fragrant bitter weed SEINet, Southwestern Biodiversity, Arizona chapter
Hymenoxys odorata is an annual herb producing a branching stem up to 60 centimeters (2 feet) tall. The stems are covered in a foliage of short leaves which are divided into narrow, pointed lobes. Each of the many flower heads contains 50–150 bright yellow disc florets and 8–13 short yellow ray florets.Flora of North America, Hymenoxys odorata de Candolle 1836. Western bitterweed, bitter rubberweed
Hymenoxys odorata is poisonous to livestock; it is mostly a problem of the sheep industry. The toxic compounds are sesquiterpene lactones called hymenovinPoisonous Range Plants of Temperate North America Merck Veterinary Manual and hymenoxon. When ingested by sheep the plant produces inflammation of the stomach, renal necrosis, and toxic hepatitis, as well as inhibition of clotting factors. An ill sheep may be bloated, anorexic, weak, drooling, and vomiting.Bitter Rubberweed (Hymenoxys odorata) USDA Poisonous Plants Research Acute and chronic, cumulative poisoning is often fatal. Sheep tend to avoid the plant because they find it distasteful but they will eat it in the absence of other forage.
References
External links Jepson Manual Treatment, University of California United States Department of Agriculture Plants Profile Photo of herbarium specimen collected in Nuevo León in 2000