We're not sure exactly what they understand not to eat. You have to be extemely careful about plant life around the habitat because if they do not know not to eat the plants, they can die from poisoning. Obviously, this does not help your edible plants. We would be very hesitant to provide a list that they will not eat because most are poisonous.

Bushes such as hawthorne with little flowering may help out or small perimeter fencing to train the birds not to go into the area may even be beneficial. We will tell you that any flowering plant, especially red flowers or red parts like salvia, petunias, choleas etc., attract the swans to eat because of their green leaves. They will also eat periwinkles and other salad like plants. NEVER USE LANTANA as this will kill the birds. Good luck. The Regal Swan