ombú, large evergreen tree (Phytolacca dioica) of the pampas of Argentina and Uruguay. It has an umbrellalike spread of foliage; the trunk may attain a girth of 40 to 50 ft (12.2-15.2 m). The tree grows rapidly. Its wood is spongy and soft enough to be cut with a knife. The ombú is the only tree native to the pampas, where it presents a solitary and distinctive aspect and provides welcome shade. Because the sap is poisonous, the ombú is not browsed by cattle and is immune to locusts and other pests. The dark, glossy leaves are sometimes used locally for a brew. The ombú is of the same genus as the North American pokeweed. It is planted as a shade tree in S California. Ombú is classified in the division Magnoliophyta, class Magnoliopsida, order Caryophyllales, family Phytolaccaceae.