Some of the most commonly found plants that are known to be toxic to chickens include daffodils, morning glory, jimson weed, tulips, nightshades, castor beans, trumpet vines, and yew. Some chickens will avoid these plants entirely, others will eat a small amount before recognizing they are not good for them. Chickens generally know what plants to stay away from. However, you should ensure these plants and other known toxic substances, are not available or provided to your flock.