While many greens are nutritious for bearded dragons, some types of greens can be toxic and should be avoided. These include: Rhubarb: The leaves of this plant contain oxalic acid, which can be toxic to reptiles and cause kidney damage. Nightshade plants: These plants, which include tomatoes, potatoes, and peppers, contain solanine, a toxic alkaloid that can cause digestive upset, weakness, and even death. Avocado: Avocados contain persin, a fungicidal toxin that can cause digestive upset and potentially other harmful effects in reptiles. Brassica family plants: These plants, which include kale, collard greens, and broccoli, contain goitrogens, compounds that can interfere with thyroid function. They should be fed in moderation.