They might look harmless, but plants can kill! Some of the deadliest poisons on earth come from plants, and they can produce frightening effects. Here are five of the deadliest plants.

5. White Snakeroot (argentina altissima)

At the age of 34, Abraham Lincoln’s mother was killed by this unassuming plant. Nancy Hanks Lincoln was killed by drinking the milk of a cow who had grazed on the plant. White snakeroot is a plant that produces clusters of small, white flowers and contains a toxic alcohol called trematol. This can then be passed through a cow’s milk and meat to unsuspecting people. Symptoms of “milk poisoning” include loss of appetite, nausea, weakness, abdominal discomfort, reddened tongue, abnormal blood acidity, and … death. Luckily, farmers are now aware of this deadly plant and remove it from pastures.

4. Oleander (nerium oleander)

Described by Pliny the Elder, a Roman scholar and personal friend of the emperor Vespasian, oleander is a beautiful plant known for its striking flowers. It is commonly grown as a hedge and ornamental, all parts of the plant are deadly and contain lethal cardiac glycosides known as oleandrin and nerine. If consumed, oleander can cause vomiting, diarrhea, irregular heartbeat, seizures, coma, and … death. Even skin contact with the leaves and sap can cause a severe reaction in some people. The toxins are so powerful that some people have even become ill by eating honey made by bees that visited oleander blossoms. Luckily, the plant is very bitter so poisonings are a rare occurrence.

3. Castor Beans (ricinus communis)

On September 7, 1978, Georgi Markov walked across Waterloo Bridge spanning the River Thames, and waited at a bus stop to get to his job at the BBC. He felt a slight sharp pain, like a bug bite or sting, on the back of his right thigh. He looked behind him and saw a man picking up an umbrella off the ground. The man hurriedly crossed to the other side of the street and got in a taxi which then drove away.

When he arrived at work at the BBC World Service offices, Markov noticed a small red pimple had formed at the site of the sting he had felt earlier and the pain had not lessened or stopped. He told at least one of his colleagues at the BBC about this incident. That evening he developed a fever and was admitted to St James' Hospital in Balham, where he died four days later.

Due to the circumstances and statements Markov made to doctors expressing the suspicion that he had been poisoned, the Metropolitan Police ordered a thorough autopsy of Markov's body. Dr Bernard Riley, a forensic pathologist discovered a spherical metal pellet the size of a pin-head embedded in Markov's leg. The pellet measured 1.70 mm (0.07 in) in diameter and was composed of 90% platinum and 10% iridium. It had two holes with diameters of 0.35 mm (0.01 in) drilled through it, producing an X-shaped cavity. Further examination by experts showed that the pellet contained traces of a deadly poison. A sugary substance coated the tiny holes creating a bubble which trapped the poison inside the cavities. The specially crafted coating was designed to melt at 98 degrees Fahrenheit (human body temperature). As the pellet was shot into Markov from a pneumatic gun disguised as an umbrella, the coating melted and the poison was free to be absorbed into the bloodstream and kill him. Regardless of whether the doctors treating Markov had known that the poison, the result would have been the same, as there was no known antidote at the time.

Widely grown as an ornamental, the castor bean is an attractive plant native to Africa. While the processed seeds are a source of castor oil, they naturally contain the poison ricin and are deadly in small amounts. It only takes one or two seeds to kill a child and about 8 to kill an adult. Ricin works by inhibiting the synthesis of proteins within cells and can cause severe vomiting, diarrhea, seizures, and … death.

2. Rosary Pea (abrus precatorius)

These piously-named seeds contain abrin. Like ricin, abrin interferes with a cell’s ability to synthesize protiens. Swallowing any amount of abrin can lead to severe symptoms. Early symptoms include nausea, vomiting, pain in the mouth, throat, and esophagus, diarrhea, dysphagia (trouble swallowing), and abdominal cramps and pain. As the symptoms progress, bleeding and inflammation begins in the gastrointestinal tract. The affected person can vomit up blood (hematemesis), have blood in their feces, and more internal bleeding. Loss of blood volume and water from nausea, vomiting, diarrhea, and bleeding causes blood pressure to drop and organ damage to begin, which can be seen as the person begins to have somnolence/drowsiness, hematuria (blood in the urine), stupor, convulsions, polydipsia (excessive thirst), and oliguria (low urine production). This ultimately results in multi-system organ failure, hypovolemic shock, vascular collapse, and … death.

1. Tobacco (nicotiana tabacum)

Yes. Tobacco, the most widely grown commercial non-food crop in the world. All parts of the plant, especially the leaves, contain the toxic alkaloids nicotine and anabasine, and can be fatal if eaten. Despite its designation as a cardiac poison, nicotine from tobacco is widely consumed around the world and is both psychoactive and addictive. Tobacco use causes more than 5 million deaths per year, making it perhaps the deadliest plant on earth.

Five Deadly Plants

5. White Snakeroot (argentina altissima)

4. Oleander (nerium oleander)

3. Castor Beans (ricinus communis)

2. Rosary Pea (abrus precatorius)

1. Tobacco (nicotiana tabacum)