Rayless goldenrod (
Haplopappus heterophyllus, previously called
Isocoma pluriflora) is an erect, bushy, unbranched perennial shrub which is toxic to horses and other animals. The plant is native to the Southwestern United States and Northern Mexico. It has narrow leaves and clusters of yellow flower heads at the top of the stems, each head with 8 to 21 yellow disc flowers.
Rayless Goldenrod Toxic Components
All parts of rayless goldenrod are toxic. It contains trematone, which is the same toxin found in
white snakeroot (Eupatorium rugosum). Horses need only eat 1-1.5% of their body weight until they begin to demonstrate signs of poisoning. Cases of poisoning are sporadic due to the considerable variation in the quantity of its toxins, differing plant to plant.
