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. In fact, according to the Toxic Exposure Surveillance System (TESS), there were 847 known human poisonings in the United States related to oleander in 2002.