Toxicity to pets

All parts of the Hydrangea plant contain cyanide-containing compounds. When the plant material is chewed or damaged (e.g., frost, crushing) free cyanide can be released triggering cyanide poisoning when ingested. Cyanide reduces the body’s ability to process oxygen at a cellular level resulting in clinical signs including vomiting, drooling, gasping, collapse, seizure, and death. The occurrence of cyanide poisoning from ingestion of this plant is higher in livestock – animals that consume large amounts and chew their food well – vs. companion animals.