Most hoary alyssum toxicity in horses is the result of the plant being baled in hay. Generally, horses will refuse the plant in pasture if other more palatable options are available. However, there have been some horses affected by what appears to have been hoary alyssum poisoning from ingestion of the plant while on pasture. Hoary alyssum has white flowers. Each flower has 4 petals. The petals are deeply divided to form 8 half-petals.
