Eulychnia acida, locally known as 'copao', is columnar cactus that varies in habit, usually treelike 1.5-4(-7) meters high, with a definite trunk 1 meter long and then more or less branching, forming a more or less rounded top, but sometimes shrubby, much branched, without trunk, forming a low mass 1 meter high or less, with branches often procumbent or ascending. Often plants have not any symmetrical or regular development, so many of them are raggedy and sometimes downright ugly for their constant struggle for moisture. Eulychnia acida are fiercely spiny even as seedlings. The fruit is edible, almost naked without wool and or porrect spines.