The San Pedro cactus (Echinopsis pachanoi) is a tall, columnar cactus native to the Andes Mountains in South America. It can grow up to 20 feet tall and is characterized by its green, ribbed stems. This cactus thrives in dry, sunny environments and is often found in rocky areas. Traditionally, the San Pedro cactus has been used in indigenous cultures for its psychoactive properties, primarily due to the presence of the chemical compound mescaline. It is commonly used in spiritual ceremonies and healing practices. In addition to its cultural significance, the cactus is also popular in ornamental gardening.