Hydrangea is a colorful flowering plant native to Asia and the Americas. It flowers from late spring through fall, and gardening enthusiasts enjoy experimenting with the flowers' ability to change color when the shrub is planted in different soils. Although hydrangeas' attractive flowers grace many a garden, dog and cat owners need to watch their pets around this plant.
Hydrangea leaves and buds are toxic to dogs, cats and horses. These parts of the plant contains cyanogenic glycosides, more commonly known as prussic acid or cyanide. If a pup chews on the plant, the chewing action releases the toxins. Symptoms of poisoning include vomiting, diarrhea and depression. Serious poisoning is rare, and most animals who eat hydrangea suffer gastrointestinal upset, according to the American Society for the Prevention of Cruelty to Animals. Symptoms usually appear within 15 to 20 minutes to a few hours after eating the plant. Consult your vet immediately if your pup shows signs of illness after playing near this plant.