They can get into any number of things that are no good for them, and ingesting something hazardous can take only a second even if you are in the room. Keep household products or anything toxic out of your dog's reach, and never keep them in an area where your dog might sleep or play. To prevent your dog from being poisoned by a plant do thorough research on which plants are toxic, and which could kill your dog. In considering the risk to your dog from these plants, you need to take into account your dog's age and how likely it is to chew on plants. For puppies, it's probably best to keep all plants out of reach.
Dumb cane can be potentially fatal if a dog has even a little nibble.
There are also a number of plants that have toxic oxalates, which irritate. These can cause the mouth to swell, and in severe cases, if the mouth swells quickly the dog can become asphyxiated. Other plants that are toxic but not potentially fatal can cause vomiting, abdominal pain or cramps in your dog. If your dog begins exhibiting any of these types of symptoms consult your vet immediately. Many plants used in Christmas decorations can be harmful or toxic to dogs.