Poisonous Iris Plant Parts
Yellow iris, known botanically as iris pseudacorus--or commonly as pale yellow iris or yellow flag--is a flowering plant whose internal liquids are a severe irritant to the skin, and whose underground rhizomes are highly poisonous and deadly to animals and humans if ingested. This is problematic because the plant is invasive and readily naturalizes. For these reasons, its propagation and planting is banned in some regions. Some of these same poisonous properties are shared with some blue or purple iris species.
Contact Irritation & Burns
The plant sap from the leaves, flower stalks and flowers themselves can create irritations, chemical burns, sores and scabbing on the skin and mucous membranes of humans and animals. The chemical action of the toxic substance in yellow iris is not well understood, but thought to be iridin, according to a study by M.R. Cooper and A.W. Johnson entitled "Poisonous Plants in Britain and Their Effects on Animals and Man."
The underground rhizomes of yellow iris are deadly to animals and humans when ingested. The mucous membranes of the mouth, throat and intestinal tract are irritated and burned. Severe pain in the abdominal and intestinal tract occurs, glands swell and the stool becomes bloody with death typically following in a few days. Autopsies on poisoned animals have shown consistent evidence of multiple critical internal organs being affected, including the kidneys and liver.