Foxtail fern, or Asparagus densiflorus Meyersii, is a plant that is closely related to the familiar garden asparagus. It is also commonly referred to as the asparagus fern and the emerald fern. It has berries that are toxic to both animals and humans.ontact Symptoms. Foxtail fern is not only toxic if ingested. The plant itself can cause skin irritation, especially if the animal repeatedly rubs against it. Skin can begin to burn or itch. Irritation usually subsides after several minutes, but the plant should be kept out of reach of pets.