There are a few vegetables to avoid feeding your dog at all times. Onions, garlic, wild mushrooms and rhubarb can be extremely toxic to your pet.
Onions contain an ingredient called thiosulphate which is toxic to cats and dogs. The ingestion of onions, onion powder, or even cooked onion causes a condition called hemolytic anemia, which is characterized by damage to the red blood cells. In other words, onion toxicity can cause the red blood cells circulating through your pet’s body to burst. A small amount can be toxic to your dog or cat.
Wild mushrooms — which may be found growing in your backyard or on the nature trail where you walk your dog — contain toxins that will trigger numerous organ systems, including the kidneys, liver and brain. Nervous system abnormalities, seizures, coma, vomiting, and death can all result when a dog consumes mushrooms.
Rhubarb contains oxalates which trigger abnormalities with the nervous system, kidneys and digestive tract. The vegetable is also commonly used in recipes for pies, jams, jellies, sauces and juice.