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ANSWER: Manchineel tree

The manchineel tree (Hippomane mancinella, Manchineel, Tree of Death) is an aptly named tropical tree designated by the Guinness Book of World Records in 2011 as The Most Dangerous Tree — a plant whose bark is as bad as its bite.

H. mancinella is found widely in the Caribbean, coastal Mexico, West Africa, Puerto Rico, and some areas of Florida and the Virgin Islands. It forms dense groves primarily on beaches or in mangroves where its roots limit coastal erosion and provide nesting for birds and insects.

Leaves of the manchineel tree are deep green, pointed and oval, about 2-3 inches long with a deep central vein sulcus. Click to enlarge. (THOMAS NUTTALL, COURTESY OF THE NEW YORK PUBLIC LIBRARY.)

Plant description: The manchineel tree is an attractive tall shrub or round-topped tree that can reach 30 to 40 feet in height and grows in high-salt environments. The plant is identified by: bark that is brownish-grey, deeply furrowed, and smooth; leaves that are deep green, pointed, 2- to 3-inch ovate with a deep central vein sulcus; milky white sap or latex that leaks from any cuts or breaks in the plant; and fruits that are deeply green when ripe, often clustered, walnut-sized and round, and have a sweet smell if you take a whiff (but don’t do it).

Exposure

“The manchineel is one of the most notorious of all irritant trees…”.⁹ Every part of this plant is extremely toxic. Not only is this plant “don’t touch,” it is also a “don’t be near” organism. The sap is so irritating that people have sustained blistering and burns after seeking shelter under the tree from the rain by contact with the water-soluble diterpene ester-containing latex contaminating the leaf run-off or in the puddles beneath the tree; burning the wood or leaves results in ocular and pulmonary injury from the downwind exposure to the smoke and ash. The sawdust from fresh wood causes severe rhinitis and cough, and many cabinetmakers refuse to work with it.⁴ 

Beware the tree of death’s white, milky sap. Click to enlarge.

At Risk

The most frequently manchineel-exposed people described in the literature are 1) tourists, 2) woodcutters, 3) military troops, 4) manchineel researchers.

Toxins

Although many are listed, the most cited chemicals or compounds found in the manchineel includes diterpene esters (responsible for skin and eye irritation) and huratoxin, hippomanin A and B, and various phenolic compounds responsible for gastrointestinal (GI) and systemic toxicity. Physostigmine was initially thought to be present in the manchineel fruits, but this has not been borne out in subsequent reports.⁶ An analysis of the fruits in a study of 97 cases of manchineel fruit poisoning failed to identify physostigmine.²