There are hundreds of plants toxic to dogs, but no single comprehensive list shows every potentially dangerous species. If you have a dog, carefully research every plant in your garden to make sure that it is canine safe, rather than taking a chance on an unknown plant. Alternately, you may use an enclosed dog run to protect your pooch from suspect plants.
Fruits in general are not healthy for dogs, but parts of the apricot, cherry, peach and apple trees are particularly toxic. The seeds, leaves and stems all contain cyanide. Dogs that have been poisoned will pant and have difficulty breathing. Their pupils will dilate and their mucous membranes will turn brick red. In some case, dogs may go into shock.
Lily of the Valley
Lily of the Valley is "particularly toxic" according to Dog First-Aid 101. This garden plant, known as Convalaria majalis, can cause an array of symptoms including vomiting, seizures, irregular heartbeat, loss of muscle control, coma and death. The Lily of the Valley Bush Pieris japonica is a different species, but also highly toxic and can cause vomiting, seizures, coma and death after consuming only a few leaves.
The entire genus of cyclamens, or sowbread, is toxic to dogs. Eating these plants can cause an array of digestive complaints including vomiting, diarrhea and excessive salivation. If a dog eats a large quantity of cyclamen tubers, it can lead to more serious symptoms including heart arrhythmia, seizures and even death.
Foxglove, or Digitalis purpurea, is a flower with tall, blooming cones. It is quite toxic, however and can be lethal to dogs. Foxglove poisoning causes vomiting and diarrhea, and can cause irregular heartbeat or heart failure.
Toxic shrubs are among the deadliest poisons for dogs according to Dog First-Aid 101. A large number of shrubs can cause symptoms in dogs. Among the worst are cycads, heavenly bamboo, oleander, precatory Bean, rhododendron and sago palm, all of which can cause death.