Scientific Name: Isocoma pluriflora
Distribution: Southwestern United States and Mexico
Type of Poison: Tremetol
Signs of Poisoning:
Growth Characteristics: An erect, bushy, unbranched perennial shrub, growing from 2 to 4 feet tall.
Flower and Fruit: Clusters of rayless yellow flowers at the top of the stems. Fruit is an achene.
Leaves: Alternate, linear, and sticky. Leaves are bright green when first emerging but darken throughout the growing season. Leaf color can also vary with the dryness of the habitat, being more gray in dry conditions and more green in wet.
Rayless goldenrod grows on the dry rangeland of the Southwest. It grows especially well in river valleys and along drainage areas. Poisoning is most common in late fall and winter.
Rayless goldenrod is toxic to horses, cattle, sheep, and goats. The toxin is present in both green and dried plant material. Daily consumption of 1 to 1.5% of the animal's weight of the green plant for one to three weeks will produce signs of poisoning in horses, cattle, and sheep. Death will result if the affected animals are not removed from access to the plant early. The condition it produces in cattle is known as trembles. The toxic substance is excreted in the milk of lactating animals so that the young may become poisoned by the consumption of contaminated milk. Humans can also be affected by consuming milk from poisoned animals.
Poisoning of livestock by rayless goldenrod can best be prevented by preventing livestock from grazing on ranges infested with this plant for extended periods.
L.F. James, R.F. Keeler, A.E. Johnson, M.C. Williams, E.H. Cronin, and J.D. Olsen. Plants Poisonous to Livestock in the Western States. U.S. Department of Agriculture, Agriculture Information Bulletin 415, 90 pp. 1980.