Citrus plants and peels (rutaceae family)

Toxic components: essential oils and psoralens
“Many [citrus] plants that produce edible fruit – including grapefruit, oranges and lemons – are toxic if the actual plant portion is ingested. For example, the skin of the fruit, the leaves, or stems can often be dangerous,” says Dr Zacharias.
Whether you grow these plants in your yard or bring them into your home from the grocery store, keep your dog away from them. Reactions may not be as severe as with other plants toxic to dogs, but if you suspect consumption, call your vet for guidance. They may request that you bring your dog in, especially if severe symptoms occur.
Oleander (nerium oleander)

Toxic component: cardiac glycosides
Oleander, known for its white or pink flowers and height that provides privacy between yards, is another poisonous plant for dogs.
“Oleander ingestion causes extreme salivation, abdominal pain, vomiting, diarrhoea and lethargy. In severe cases, it causes liver failure and death, and it can ultimately interfere with the heart’s ability to beat properly,” explains Dr Long. “Once it is known that the dog ingested these poisonous leaves, rapid transfer to a veterinary hospital where vomiting can be induced is key. Supportive therapy with drugs designed to control gastrointestinal signs, as well as reverse liver and heart issues, is key to survival.”
Snake plants (sansevieria trifasciata)

Toxic component: saponins
Because of its striking appearance and the fact that it’s a houseplant that’s very hard to kill, snake plants are found in houses all across the world. Unfortunately, they are also poisonous plants for dogs and can cause nausea, vomiting and diarrhoea if consumed. It’s important to contact your veterinarian right away if you think your dog has ingested any portion of a snake plant. Depending on the severity, you may need to simply monitor and treat your dog’s symptoms, or you may need to take your dog in for more aggressive treatment.