Oleander is one of the most toxic, commonly grown garden plants in the world — and oddly enough, it's often found in schoolyards. Ingesting any part of this plant can be deadly, especially for children. Even smoke from burning oleander can be fatal.
The plant's use as a poison is well-known, reports WebMD. Oleander is reportedly a favorite suicide agent in Sri Lanka, where oleander poisonings exceed 150 per 100,000 people each year. About 10 percent of those cases are fatal.