Common garden plants that are poisonous to rabbits include the eggplant, potato plant, sweet potato plant, tomato plant and the root of mustard plants. Besides the potato plant, the eyes of a potato can also harm rabbits.
Many foods easily digested by humans can cause sickness or even death in a rabbit. Besides the common garden plants mentioned, the pits and seeds of some fruits can cause problems for a rabbit's digestive system. The seeds of apples and pears and the pits of apricots, peaches and plums contain minute amounts of cyanide that are enough to kill a rabbit. Almonds, cassava roots, mangoes and millet sprouts also contain this ingredient. Persin in avocado fruit, seeds, leaves and bark is harmful to a rabbit, along with a substance called Psoralens found in parsnips. Rabbits should not eat the bark and twigs of cherry trees. Rhubarb and spinach are harmful, though not usually fatal. Some foods, such as mushrooms, may have negative long-term effects on a rabbit.
If it is suspected that a rabbit has digested any of these foods, a visit to the veterinarian is needed. It may take several days for the symptoms of ingesting these foods to become apparent.