Excoecaria is a genus of flowering plants in the family Euphorbiaceae (order Malpighiales), formally described by Carl Linnaeus in 1759. The genus belongs to the Old World Tropics, with species distributed across Africa, southern Asia, northern Australia, and various oceanic islands.
Members of Excoecaria are trees and shrubs characterised by a milky, highly caustic latex that has given the genus both its scientific name and many of its common names. The most prominent species, Excoecaria agallocha — known as the blind-your-eye mangrove, milky mangrove, or river poison tree — is a true mangrove associate found in coastal wetlands and tidal zones throughout tropical Asia and northern Australia. Its latex causes rapid blistering on skin contact and temporary blindness on contact with eyes; even dried and powdered leaves retain toxins potent enough to kill fish.
A second widely cultivated species, Excoecaria cochinchinensis (Chinese croton), is grown ornamentally for its striking bicoloured foliage — deep green above and vivid red-purple beneath — and is common in tropical and subtropical gardens across Asia and beyond.
The genus was once considerably larger but has been substantially revised: numerous former members have been transferred to related genera including Sapium, Gymnanthes, Sebastiania, Stillingia, Triadica, Homalanthus, Neoshirakia, and others, reflecting advances in molecular phylogenetics within the tribe Hippomaneae of Euphorbiaceae.
Etymology
The genus name Excoecaria derives from the Latin excaeco, meaning "to blind." It refers to the caustic milky sap produced by species in the genus, which can cause temporary blindness if it contacts the eyes.
Distribution
Excoecaria is native to the Old World Tropics, with its range spanning Africa, southern Asia, northern Australia, and various oceanic islands. Excoecaria agallocha, the best-known species, occurs in mangrove and coastal wetland habitats from India (including the Pichavaram wetlands near Chidambaram, Tamil Nadu) through Southeast Asia and Australia, from northern New South Wales along the northern coastline to Western Australia.
Ecology
Species of Excoecaria produce a milky latex that is highly toxic to animals and humans. Contact with skin causes irritation and rapid blistering; contact with eyes results in temporary blindness. Excoecaria agallocha is a mangrove-associated species of coastal and tidal environments. Its toxicity extends to dried and powdered leaf material, which is lethal to fish — a property historically exploited as a fish poison in parts of its range.
Cultural Uses
Excoecaria agallocha has long been associated with the Thillai Chidambaram Temple in Tamil Nadu, India, where mangroves of this species surround the ancient site — giving the location its name ("Thillai" is a local name for the plant). The toxic latex has also been used traditionally as a fish poison across parts of tropical Asia and the Pacific.
Taxonomy Notes
Excoecaria was described by Linnaeus in 1759 and was historically circumscribed to include many more species than are currently accepted. Molecular and morphological revisions have led to the transfer of numerous former species to related genera, including Actinostemon, Adenopeltis, Alchornea, Anomostachys, Bocquillonia, Bonania, Cerbera, Falconeria, Grimmeodendron, Gymnanthes, Homalanthus, Maprounea, Microstachys, Neoshirakia, Sapium, Sclerocroton, Sebastiania, Shirakiopsis, Spirostachys, Stillingia, and Triadica. GBIF currently recognises 9 accepted species in the genus.
