Triplaris americana is a species of flowering plant in the knotweed family known by many common names, including ant tree or pau-formiga ("ant tree"), guacamayo, guayabo zancón, hormiguero, palo de Santa María, tachí, vara santa, pau-de-novato, formigueiro, and taxizeiro. It is native to Central and South America, occurring from Panama to Brazil. It is also cultivated as an ornamental for its showy pink flowers.
This species is a tree growing up to 30 meters in height with a trunk diameter reaching 30 centimeters. The smooth bark is a mottled gray color. There are ochrea up to 12 centimeters in length. The leaves are oval to oblong and measure up to 40 centimeters long by 20 wide. The undersides are sometimes woolly with brown fibers. The tree is dioecious. The male flowers are around 2 millimeters long, while the female flowers are up to 5 centimeters long. The sex ratio of the species is skewed, with many more female plants than male.
This species is a myrmecophyte, forming a mutualistic relationship with ants. Ants living on the plant include Pseudomyrmex triplarinus. This species lives within the tree, feeding on substances produced by it, and defending it against invaders. This tree is known as a "novice tree" (pau-de-novato) because only one unfamiliar with the tree would touch it, soon discovering that the ants are aggressive and venomous.
This tree is considered a noxious weed in southern Africa. The fruits are dispersed on the wind and the seedlings easily take hold and become invasive, growing in the local habitat and displacing native plants.