Vegetables such as spinach, lettuce, beets, celery stalk, romaine, onions, and beet greens have proven to be poisonous to iguanas. Other notable examples include bananas, carrots, grapes, kale, broccoli, turnips, cauliflower, Chinese cabbage, and Brussel sprouts. If you’re rearing iguana as a pet, you need to avoid these plants as they are toxic. But if you’re looking for ways to eliminate them once and for all, planting these plants in your yard will go a long way.