Soak up this citrusy blend of the naturally caffeinated leaves of the yerba mate plant. Yerba mate (yer-bah ma-tay), known scientifically as Ilex paraguariensis, is a tree of the holly family that is native to the Atlantic Forest of South America. In Argentina, Brazil and Paraguay, yerba mate is commonly cultivated, but in the forest, a mate tree can grow up to 30 meters (almost 100 feet) in height!