Trichocereus macrogonus var. pachanoi

Trichocereus macrogonus var. pachanoi is native to Ecuador and Peru. Its stems are light to dark green, sometimes glaucous, with a diameter of 6–15 cm (2.4–5.9 in) and usually 6–8 ribs. The whitish areoles may produce up to seven yellow to brown spines, each up to 2 cm (0.8 in) long although typically shorter in cultivated varieties, sometimes being mostly spineless.[4] The number and length of the spines is a feature that distinguishes T. macrogonus var. pachanoi from var. macrogonus, which may have up to 20 spines with three or four longer and more robust central ones up to 5 cm (2.0 in) long.[8] The areoles are spaced evenly along the ribs, approximately 2 cm (0.8 in) apart.[5] Trichocereus macrogonus var. pachanoi is normally 3–6 m (10–20 ft) tall and has multiple branches, usually extending from the base but will emerge around broken branches.[4] The tallest recorded specimen was 12.2 metres (40 ft) tall.[5] White flowers are produced at the end of the stems; they open at night and last for about two days. Large numbers can be produced by well established cacti and may open new flowers over a period of weeks. The flowers are large, around 19–24 cm (7.5–9.4 in) long with a diameter of up to 20 cm (7.9 in) and are highly fragrant. There are black hairs along the length of the thick base leading to the flower. Oblong dark green fruits are produced after fertilization, about 3 cm (1.2 in) across and 5–6 cm (2.0–2.4 in) long,[4] eventually bursting open to reveal a white flesh filled with small seeds.

Trichocereus macrogonus var. pachanoi was first described as the species Trichocereus pachanoi by Britton and Rose in 1920. As a species, it has also been placed in the genera Cereus and Echinopsis. It was reduced to a variety of Trichocereus macrogonus in 2012. It can be distinguished from T. macrogonus var. macrogonus by the smaller number of spines per areole, and usually being somewhat shorter with more slender stems.[8]

Hordenine, an alkaloid found in Trichocereus macrogonus var. pachanoi

Trichocereus macrogonus var. pachanoi, San Pedro Cactus, the tall cactus in the mid-foreground, in its natural habitat in Peru. Several fruits with shrivelled flowers can be seen.

Trichocereus macrogonus var. pachanoi is known by many names throughout South America such as achuma, huachuma, wachuma, aguacolla, hahuacollay, San Pedro or giganton.[9][10] It has a long history of being used in Andean traditional medicine. Archaeological studies have found evidence of use going back two thousand years, to Moche culture,[11] Nazca culture,[12] and Chavín culture. Although Roman Catholic church authorities after the Spanish conquest attempted to suppress its use,[13] this failed, as shown by the Christian element in the common name "San Pedro cactus" – Saint Peter cactus. The name is attributed to the belief that just as St Peter holds the keys to heaven, the effects of the cactus allow users "to reach heaven while still on earth."[14] In 2022, the Peruvian Ministry of Culture declared the traditional use of San Pedro cactus in northern Peru as cultural heritage.[15]

Sliced to be brewed

Trichocereus macrogonus var. pachanoi contains a number of alkaloids, including the well-studied chemical mescaline (from 0.053% up to 4.7% of dry cactus weight),[16] and also 3,4-dimethoxyphenethylamine, 3-Methoxytyramine, 4-hydroxy-3-methoxyphenethylamine, 4-hydroxy-3,5-dimethoxyphenethylamine, anhalonidine, anhalinine, hordenine, and tyramine.[17]

Mescaline is a psychedelic drug and entheogen, which is also found in some species of the genus Echinopsis (e.g. Echinopsis lageniformis and Echinopsis scopulicola) and the species Lophophora williamsii (peyote).[18] Mescaline induces a psychedelic state comparable to those produced by LSD and psilocybin, but with unique characteristics.[19]

Anecdotal evidence suggests that the highest concentration of active substances is found in the layer of green photosynthetic tissue just beneath the skin.[5][20]

A small newly planted Trichocereus macrogonus var. pachanoi (San Pedro Cactus) cutting

Trichocereus macrogonus var. pachanoi in USDA hardiness zones 8b to 10.[21] The range of minimum temperatures in which it is known to grow is between -9.4 °C and 10 °C.[22] Because it grows naturally in the Andes at high altitude and with high rainfall, it can withstand temperatures far below that of many other cacti. It requires fertile, free-draining soil. Plants grow up to 30 cm per year.[5][23] They are susceptible to fungal diseases if over-watered, but are not nearly as sensitive as many other cacti, especially in warm weather. They can be sunburned and display a yellowing chlorotic reaction to overexposure to sunlight.

In winter, plants will etiolate, or become thin, due to lower levels of light. This may be problematic if the etiolated zone is not sufficiently strong to support future growth as the cactus may break in strong winds.

In most countries, it is legal to cultivate Trichocereus macrogonus var. pachanoi. In countries where possession of mescaline and related compounds is illegal and highly penalized, cultivation for the purposes of consumption is most likely illegal and also highly penalized. This is the case in the United States, Australia, Canada, Sweden, Germany, and New Zealand, where it is currently legal to cultivate the San Pedro cactus for gardening and ornamental purposes, but not for consumption.

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  Seeds
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  Three-week-old seedling
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  Five-month-old seedling
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  The fruit after bursting open, revealing the seeds in a sweet flesh.

• Ayahuasca
• Cimora
• List of psychoactive plants
• Psychedelic microdosing
• Stela of the cactus bearer

• Jay, Mike (2019). Mescaline: A Global History of the First Psychedelic. Yale University Press.
• Pollan, Michael (2021). This Is Your Mind on Plants. Penguin Press.
• Sharon, Douglas (2000). Shamanism & the Sacred Cactus: Ethnoarchaeological Evidence for San Pedro Use in Northern Peru. San Diego Museum of Man.

Wikimedia Commons has media related to Trichocereus macrogonus var. pachanoi.

• Cactus Culture Volume 1: Trichocereus by Patrick Noll
• San Pedro: Basic Info – International Center for Ethnobotanical Education, Research, and Service (ICEERS)
• Psychoactive Cacti vault – Erowid