When your furry friend has plant poisoning, it will show the following symptoms: vomiting, diarrhea, drooling, and muscle tremors. The key symptom is vomiting. This vomiting can be either from the mouth or from the stomach. If the vomit is from the mouth, the vomit is usually yellow. If the vomit is from the stomach, the vomit will be greenish and contains undigested grass. The color of the vomit and the time it is vomited usually help to determine if your furry friend has plant poisoning. If the color and time are consistent with plant poisoning, then you should take your furry friend to a vet.