Huachuma is a cactus native to the Andean highlands. It has been more commonly referred to as San Pedro since the time the conquistadors encountered its use some five-hundred years ago. Some say that the conquistadors experienced the medicine as opening the gates of heaven, thus naming it after Saint Peter, or San Pedro in Spanish. The Huachuma cactus is not a single variety, but a number of interrelated species within the classification Trichocereus pachanoi (also called echinopsis pachanoi). The varieties range from thin nearly spineless cactus that grow in the lowland deserts to thick varieties with long spines, which grow more commonly in the Andes mountains at higher elevations. In the United States, a few strains of hybrid San Pedro have been cultivated for decades for ornamental gardening purposes. Many people are often surprised to learn that they have these plants growing in their neighborhoods.