The manchineel tree may be endangered, but so is anyone who messes with it. That's because this rare tropical plant, which offers deceptively sweet fruit, is one of the most poisonous trees on Earth.

Manchineels are notorious in their native habitats, the sandy soils and mangroves of South Florida, the Caribbean, Central America and northern South America. Many are labeled with warning signs like the one pictured below. But aside from poisoning the occasional conquistador, tourist and literary character, manchineel is relatively obscure considering it holds the world record for most dangerous tree.

manchineel

Manchineel trees are often marked with signs, like this one in the Cayman Islands. (Photo: Scott Hughes/Flickr)

The fruits are the most obvious threat, earning manchineel the name manzanita de la muerte, or "little apple of death," from Spanish conquistadors. Resembling a small green crabapple about 1 to 2 inches wide, the sweet-smelling fruits can cause hours of agony — and potentially death — with a single bite.

"I rashly took a bite from this fruit and found it pleasantly sweet," radiologist Nicola Strickland wrote in a 2000 British Medical Journal article about eating manchineel with a friend. "Moments later we noticed a strange peppery feeling in our mouths, which gradually progressed to a burning, tearing sensation and tightness of the throat. The symptoms worsened over a couple of hours until we could barely swallow solid food because of the excruciating pain and the feeling of a huge obstructing pharyngeal lump."

Poison apples are just the beginning, though. Every part of a manchineel is toxic, and according to the Florida Institute of Food and Agricultural Sciences (IFAS), "interaction with and ingestion of any part of this tree may be lethal." That includes bark, leaves and the milky sap, one drop of which can scorch the skin of shade-seeking beach-goers. Even without touching the tree itself, people (and car paint) have been burned by the thick, caustic sap as rain washes it off branches overhead.

manchineel fruit

A yellow manchineel fruit grows on Bastimentos Island in northwest Panama. (Photo: Dick Culbert/Flickr)

The tree holds a cocktail of toxins, including hippomanin A and B as well as some yet to be identified. A few act instantly, according to "Poisonous Plants and Animals of Florida and the Caribbean" by David Nellis, while others take their time. Symptoms from contact with sap range from a rash and headache to acute dermatitis, severe breathing problems and "temporary painful blindness," Nellis writes. Burning or chopping the wood isn't advised, either, since its smoke and sawdust burn skin, eyes and lungs.

Eating the fruit usually causes abdominal pain, vomiting, bleeding and digestive tract damage, Nellis adds. Death is widely considered a risk, but mortality data for ingesting the manchineel fruit — informally known as a "beach apple" — are scarce. And aside from the short-term danger, some manchineel compounds may be co-carcinogenic, promoting the growth of benign and malignant tumors.

The most famous victim of manchineel is probably conquistador Juan Ponce de Leon, who led the first European expedition into Florida in 1513. He returned to colonize the peninsula eight years later, but his invasion met resistance from Calusa fighters. Some native Caribbean people used manchineel sap to make poison arrows, and one of these sap-tipped arrows reportedly struck Ponce de Leon's thigh during the 1521 battle. He fled with his troops to Cuba, where he died of his wounds.

Manchineel also has peaceful uses. Normally a hefty shrub, it can grow up to 50 feet tall, producing toxic timber that has long tempted Caribbean carpenters. And despite the danger, people have used manchineel to make furniture for centuries, carefully cutting the wood and then drying it in the sun to neutralize its poisonous sap. Native people even used manchineel as medicine: A gum made from the bark can reportedly treat edema, while dried fruits have been used as a diuretic.

beach apple

A green "beach apple" braves the surf on Mayreau in the Grenadines. (Photo: Mary Witzig/Flickr)

Although manchineel sap is poisonous to birds and many other animals, there are some creatures it doesn't seem to bother. The garrobo or striped iguana of Central and South America, for example, is known to eat manchineel fruit and sometimes even lives among the tree's limbs, according to IFAS.

Plant toxins typically evolve for defense, but it's not clear why manchineel went to such extremes. Coastal living might have enabled it, since its seeds can travel by sea — sometimes across the Gulf of Mexico — rather than relying on animals. Regardless, toxicity became a liability for manchineels in Florida, where eradication efforts and habitat loss pushed it onto the endangered species list.

Yet while it's less famous than toxic plants like poison ivy or hemlock, manchineel at least has relative notoriety among endangered plants, most of which are publicly unknown. And local respect for its risks, as well as benefits, may give it an edge over endangered plants with less star power and firepower.

People tend to leave manchineel alone, both for obvious reasons and because even this poison-obsessed tree provides ecosystem services. It's a natural windbreak and fights beach erosion, for instance, a useful service in the face of rising sea levels and bigger Atlantic storms. And since biotoxins can inspire beneficial scientific breakthroughs like safer pesticides from scorpion venom or pain medicine from cone snails, it's probably worth keeping manchineel around — at a safe distance.

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.