According to the American Society for the Prevention of Cruelty to Animals, the hibiscus plant is toxic to dogs, cats and horses. When consumed, the plant can cause vomiting, diarrhea and even nausea.
Plants including the Easter lily and the hibiscus are not harmful to humans. A cat that has eaten an Easter lily will eventually go into renal failure while a dog that eats a hibiscus will vomit so hard it may begin vomiting blood. The loss of fluid that can result from the stomach upset can often be fatal. Holly berries are another plant product that can be extremely harmful to pets when ingested.