San Pedro cactus (Trichocereus pachanoi or Echinopsis pachanoi) is a large succulent with a columnar growth habit, named after Saint Peter--the Catholic saint thought to guard the gates of heaven. Used in rituals and divination by Native American populations for more than 2,000 years, San Pedro cactus is also a popular ornamental plant in the Southwest. It grows well in full sun with little supplemental water. It has a neat growth habit and is low maintenance--making it a good choice for xeriscapes around pool areas.
San Pedro cactus is a member of the Cactaceae family. It is native to the northern Andes of Peru, Ecuador and Colombia and is tolerant of cool temperatures.
San Pedro accepts heavy amounts of water when it grows in fast-draining sandy or humus-rich soils. Heavy soils combined with abundant moisture leads to rotting and the plant's demise. San Pedro can grow as tall as 20 feet in its native setting.
Color and Shape
Echinopsis pachanoi is medium to dark green. It occasionally has a bluish tinge on new growth or when grown in shade. The vertical arms are cylindrical and have between four and nine distinct vertical ribs. Small spines bunched in groups appear along the ridges of the ribs.
San Pedro has fewer and smaller spines than other varieties of Echinopsis. In arid warm climates, Echinopsis pachanoi grows up to 15 feet fall. Plant enthusiasts recognize it for its distinctive candelabra-type growth in which multiple stalks branch out from a single base.
Flowers and Fruits
San Pedro cactus has showy and fragrant blooms. Trumpet-shaped 8-inch white flowers unfurl fully at dusk and stay open at night. Bees visit the flowers during the day, and bats pollinate the flowers at night.
Rarely, plants produce edible red fruits. The plants grow at a moderate rate--faster than many other cacti or succulents. Mature San Pedro plants get top heavy--when branch segment topples over, new vertical growth sprouts from the now horizontal log. Eventually sprouts pop up along the entire length.
San Pedro cactus contains small amounts of mescaline, a psychoactive compound also found in peyote. Native Peruvians used the plant for ritual cleansing ceremonies for centuries.
South American indigenous people continue to use the plant for divination in the 21st century, and traditional medicine practitioners treat high blood pressure, heart conditions and other ailments with preparations made from the plant.
Artists and writers experimented with mescaline at the beginning of the 20th century. Aldous Huxley wrote "The Doors of Perception" about his interactions with the drug.
Possession and use of mescaline and mescaline-based compounds are illegal in the United States. Possessing San Pedro cactus for the purpose of extracting and using psychoactive compounds is forbidden. Growing the plant for ornamental value is legal.