Hydrangea
If you accidentally ingest a hydrangea, which is a common plant you’ll find in your backyard, you’ll experience skin irritation, upset stomach, convulsions, and coma. The most toxic part of the plant is the flower buds. It’s even toxic to the skin, and if touched, may cause rash or irritation. The poison comes from cyanogenic glycoside. If your pet cat happens to ingest a hydrangea, it’ll experience nausea, diarrhea, depression, breathing difficulties, and seizures (Perfect Plants).