The World's Most Dangerous Plants and Trees

Since plants and trees are unable to use movement to defend themselves from a threat, many have instead developed alternative ways of protecting themselves. From spikes, to stings, and in many cases, deadly poisons, these deadly defence mechanisms have made sure that these usually harmless looking plants are more than deserving of inclusion in a rundown of the world's most dangerous plants and trees.

hemlock - conium Hemlock (Conium)

Hemlock is a highly poisonous weed; ingestion of as few as six of the leaves can cause death by paralysis to both humans and many other animals. Paralysis usually begins in the legs and works its way upwards, until it reaches the respiratory system, causing death. In ancient Greece, Hemlock was regularly used in executions.

In very small doses, Hemlock has medicinal properties, and historically has been used as a painkiller, to help ease breathing problems such as bronchitis and asthma, and to treat anxiety. However the difference between a medicinal dose and a potentially fatal dose is so small that's it's use as a medicine has almost entirely ceased today.

Where it's found

Hemlock is native to temperate regions of West Asia, North Africa, and Europe (including the UK). It also now grows in (although is not native to) many other parts of the world including North America, Asia, Australia, and New Zealand.

Manchineel tree Manchineel Tree

Widely regarded as the world's most dangerous tree, every part of the Manchineel is so highly poisonous that the best advice you can be given is to just stay well clear of it. The tree's milky sap causes inflammation, blistering and burns. Eating the fruit (which is known by the deceptively benign name 'beach apple') causes severe gastroenteritis; expect nausea, vomiting, diarrhea, seizures, and potentially, death. If the tree is burned, the resulting smoke can cause blindness if it enters the eyes.

Historically, native Caribs would use the tree's sap to poison their arrows, while captives would sometimes be tied to the tree, resulting in a slow, painful death.

On the plus side, the tree's roots help to stabilise the sand on the beaches where it grows, helping to prevent beach erosion.

Where it's found

Florida, the Caribbean, the Bahamas, Central American, and northern South America.

Nerium Flower Nerium Oleander

Despite the fact ingestion of the Oleander can cause cardiac arrest, the flower is widely used as an decorative plant and is often planted in gardens, parks, and even schools.

Where it's found

Native to Morocco, Mauritania, Portugal, southern Asia, and southern parts of China, its use as an ornamental plant means it is regularly found worldwide.

white snakeroot White Snakeroot

White Snakeroot contains the poison tremetol (which gets its name from the tremors the poison causes), and can be fatal to humans when ingested directly. However White Snakeroot is also highly dangerous and potentially fatal when ingested indirectly - when consumed by cattle, the animals' milk and muscles become contaminated with tremetol, which if later ingested by humans can make us very ill with what's known as 'milk sickness'.

Although modern practices mean cases of milk sickness are now very rare, in the early 19th century it was the cause of thousands of fatalities in Midwest America, most notably resulting in the death of Abraham Lincoln's mother, Nancy Lincoln.

Where it's found

Primarily in the cooler climates of North America.

Cerbera odollam Cerbera Odollam (Suicide Tree)

The fruits of the Cerbera Odollam contain seeds of which the kernels hold a highly poisonous toxin called cerberin. The poison affects the heart, and consumption of it is usually fatal.

Since cerberin is tricky to detect in autopsies, and has a relatively mild taste that can be disguised with strong spices, it is commonly used in homicides and suicides.

Where it's found

Southern Asia, mainly India.

Ricinus Communis Ricinus Communis

The Ricinus Communis is most famous for its seeds which contain castor oil; a vegetable oil frequently used in cooking. Strangely, the same seeds also contain an incredibly powerful plant toxin, ricin. Ricin is more poisonous than cyanide, and even the strongest snake venom; just a few salt-sized grains is enough to kill an adult.

In the early 20th Century ricin was developed as a biological weapon to be used in World War I, although it was never used. Ricin was also developed for use in World War II, but again, the war ended without it being used.

It has recently been used in a number of (failed) terrorist attacks targeted at U.S. politicians, and was successfully used in 1978 in the assassination of Bulgarian dissident writer, Georgi Markov.

Where it's found

Primarily the Southeastern Mediterranean, India, and East Africa, however it is common to many tropical regions.


Photo credits:

Brewbooks - Harry Rose - Scott Hughes - Barry Stock - Tanaka Juuyoh - Leonora Enking - Dendroica Cerula - Homer Edward Price - Museum de Toulouse

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