5 of the Most Poisonous Tropical Rainforest Plants

Plants, unlike animals, can’t run or hide when predators come looking for food. Instead, many plants have evolved to be extremely poisonous.

Poisonous plants have evolved chemical defenses to make their leaves unpalatable to potential herbivores. The leaves can simply taste bad, make an herbivore sick, or in extreme cases, kill them outright.

Tropical rainforests are famous for their staggering diversity, and plants are no exception. Rainforest plants have developed all sorts of chemical defenses, and many of which are so extreme they can easily kill a human! Here are 5 of the most poisonous tropical rainforest plants.

[Photo by user Ray_Shrewsberry

Castor Bean (Ricinus communis)

Castor bean is originally from East Africa and is now a common ornamental plant that’s widespread throughout the tropics. The plant can grow to be up to 12 meters (39 feet) tall and has become naturalized around the world. As a weedy plant, it grows rapidly and is common on riverbanks and roadsides.

A common product from this plant is castor oil. The liquid is used in food production as a preservative, as well as in medicine for a variety of benefits. Castor oil is derived from the seeds which also contain one of the most deadly poisons known to man.

The toxin hidden inside castor bean seeds, called ricin, is notoriously dangerous. If just a tiny amount is ingested, it can kill a person in a few days. Ricin can also be turned into an aerosol and inhaled.

There have been a few instances in history where ricin has been used as a biological weapon, like the assassination of a journalist. Any part of the plant can potentially contain ricin, so consumption of the stem, leaves, and of course the fruit, is a no-go.

Photo by sarangib

Yellow Oleander (Cascabela thevetia)

This next poisonous plant on our list is basically the tropical counterpart to Nerium oleander, a common ornamental plant in temperate zones. Yellow oleander is also a common ornamental plant due to its bright yellow flowers, and it’s just as toxic as its close cousin.

Pretty much all parts of the plant contain milky sap, also called latex. The sticky substance quickly spills out of any wound, and easily deters anything from eating it. For some people, just touching the sap will result in a bad rash.

Manchineel (Hippomane mancinella)

Manchineel is a common plant that grows on beaches throughout Central and South America. It makes our list because it’s one of the most poisonous plants in the world.

Like yellow oleander, the entire plant contains white latex that can easily send you to the hospital if ingested. When the latex hits your skin, it’s possible to break out in blisters, similar to a bad burn.

There have even been reports of people falling victim to this tree just while standing under it in the rain. When rain falls through the canopy of manchineel, it’s possible a small amount of latex finds its way into the water. Contaminated raindrops that fall on a person have the ability to burn the person’s skin!

One of the most interesting things about this tree is that we still don’t know what many of the toxins are that make it so dangerous. Despite the toxicity of this plant, iguanas are known to eat the leaves and fruit, seemingly unaffected by the plant’s extreme defenses.

Gympie Gympie, A.K.A. The Suicide Plant (Dendrocnide moroides)

Gympie gympie is native to the tropical rainforests of Northeastern Australia and Indonesia. It’s in the same plant family as stinging nettle, Urticaceae.

Gympie gympie is basically the bigger, more dangerous version of stinging nettle, and it defends itself in exactly the same way. Tiny, hollow hairs cover the leaves that, when touched, pierce the skin. The hairs break off the plant and inject a toxin underneath the skin, similar to how hypodermic needles work.

After contact with the plant, the pain that ensues is apparently one of the most excruciating experiences one can endure. Instant stinging and burning are the first two symptoms and can become more intense as time goes on. The pain of a sting can last for hours or even days.

One of the worst things about this formidable plant is that the hairs are so fine and light that they often become airborne. Floating, stinging hairs can come into contact with the skin even if you’re not right next to the plant. Worse yet, they can damage your throat and lungs if inhaled.

With a name like “the suicide plant,” you should probably stay as far away as possible. But, that doesn’t stop people who study this plant, who wear respirators and special rubber gloves, to work with it!

Photo by binghamdi

Datura (Datura spp.)

Datura is another common ornamental plant on our list. It’s a member of the nightshade family, Solanaceae, which has some of the most toxic plants in the world. datura is probably the most infamous member of the nightshade family due to its extreme toxicity.

The toxin in this plant is mostly contained in the flowers and seeds, but smaller amounts can be found in the leaves and stems. Many cultures around the world use datura as both a poison and medicine.

The alkaloids in datura have psychoactive properties, which many cultures have taken advantage of. Historically, people around the world used this plant in rituals to dissociate from reality and have psychedelic experiences. But, without an intimate knowledge of the plant and how to use it, it’s extremely easy to abuse Datura. Countless people have died from attempting to eat this plant as a drug in recent years.

Although the tropics contain many poisonous plants, the rainforest is an incredible place to do some plant exploration. Just don’t go around eating everything you see!

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