San Pedro can come labeled Trichocereus pachanoi, Echinopsis pachanoi or simply San Pedro. All 3 name the same plant, and it is grown the same way under any of them. The rest of a label, such as an x between 2 names, a name in single quotes or the letters PC, tells you how the plant was bred or how it was propagated (multiplied, for example from cuttings).
The short version
- A botanical name has 2 parts: the genus, a group of related species, then the species. Trichocereus pachanoi and Echinopsis pachanoi are 2 names for the same plant, based on the same original specimen.
- Both genus names are in current use. Plants of the World Online, the plant-name database of the Royal Botanic Gardens, Kew, puts San Pedro in Echinopsis, and a 2025 DNA-based classification of the cactus family accepts Echinopsis but not Trichocereus. The Caryophyllales.org cactus checklist accepts Trichocereus as a genus of its own. A label with either name is not wrong.
- Plants of the World Online places some other plants growers call Trichocereus, such as the Argentine saguaro, in a third genus, Leucostele.
- The species part can differ as well. The plant often sold as Peruvian torch, Trichocereus peruvianus, is Echinopsis macrogona in Plants of the World Online.
- San Pedro is a common name. Use the botanical name when you need to be sure which plant you have.
- An x between 2 names marks a hybrid, a cross between them. Seed from a hybrid can give plants unlike the parent plant. A cutting gives the same plant.
- A name in single quotes after the botanical name is a cultivar: a selection whose plants share a feature and keep it when propagated.
- PC is a clone label growers and sellers use for the most common San Pedro in the United States. A clone is one plant multiplied by cuttings, so every PC plant is treated as the same plant. Where it came from is unclear.
- To check any name, search for it in Plants of the World Online. The page says whether the name is accepted or a synonym, and of what.
How a botanical name is built
The genus comes first, capitalized, and the species epithet second, in lowercase. Together they name one species: in Trichocereus pachanoi, Trichocereus is the genus and pachanoi the epithet.
"var." (variety) and "subsp." (subspecies) mark smaller groups within a species. A synonym is another name that has been used for the same plant. Databases list synonyms under the name they accept.
Why there are 2 genus names
The 2 genus names come from 2 views of where one genus ends and the next begins. Britton and Rose named the plant Trichocereus pachanoi in 1920. In 1974 Friedrich and Rowley moved San Pedro and its relatives into the larger genus Echinopsis, which gave the name Echinopsis pachanoi.
Echinopsis in that older, wider sense mixes plants from more than one line of descent, meaning separate branches of the cactus family tree. Classifications published since then redraw the genus in different ways, and they do not agree on where Trichocereus belongs.
Plants of the World Online accepts Echinopsis and lists Trichocereus as a synonym of it, so San Pedro is Echinopsis pachanoi there. The 2025 classification of the cactus family by de Vos and colleagues also accepts Echinopsis and does not keep Trichocereus as a separate genus. The Caryophyllales.org checklist (Korotkova and colleagues, 2021) accepts Trichocereus. Albesiano and Kiesling (2012) use Trichocereus too, and treat San Pedro as a variety: Trichocereus macrogonus var. pachanoi.
In Plants of the World Online, San Pedro, Peruvian torch and Bolivian torch are in Echinopsis, but some other plants growers call Trichocereus are in Leucostele: the Argentine saguaro, Trichocereus terscheckii, is Leucostele terscheckii there, and the Chilean Trichocereus chiloensis is Leucostele chiloensis.
Growers and sellers widely use Trichocereus, so search under each genus name.
When the species part changes too
Peruvian torch. It is often sold as Trichocereus peruvianus. Albesiano and Kiesling treat Peruvian torch and San Pedro as 2 varieties of one species, Trichocereus macrogonus var. macrogonus and Trichocereus macrogonus var. pachanoi. Plants of the World Online keeps San Pedro as a species of its own and lists Trichocereus peruvianus as a synonym of Echinopsis macrogona. Only the name changes, not the plant.
Spines are the feature most often used to tell the 2 apart, but a plant's spines vary in number and length with how much light it gets. Spines alone do not settle which one you have, so go by a label that gives the botanical name.
Bolivian torch. It is often sold as Trichocereus bridgesii. Under Echinopsis, the name Echinopsis bridgesii already belongs to a different Bolivian cactus, described in 1850, and the rules of plant naming do not allow 2 plants of the same rank to share one name. Plants of the World Online therefore calls Bolivian torch Echinopsis lageniformis and lists Trichocereus bridgesii as a synonym of it. It describes Echinopsis lageniformis as a succulent tree and Echinopsis bridgesii as a subshrub, a low, shrubby plant. If a label reads Echinopsis bridgesii, ask the seller which plant they mean.
Common names and botanical names
San Pedro is the plant's Spanish common name. Peruvian torch and Bolivian torch are English names used in the trade. Common names are loose: a plant can have several, and the same name can be used for different plants.
Botanical names change as plants are reclassified, and an old name stays on record as a synonym. In Plants of the World Online (powo.science.kew.org), a synonym's page names the accepted name it belongs to: a search for Trichocereus pachanoi leads to Echinopsis pachanoi.
What a hybrid name tells you
A hybrid is a cross between 2 named plant groups, such as 2 species. A hybrid formula names both parents with an x (a multiplication sign) between them, as in Trichocereus pachanoi x Trichocereus peruvianus.
Seedlings of a cross can differ from both parents and from each other, so 2 plants sold under the same cross can look different. A label that says only "hybrid" gives no parents. If the parents matter to you, ask the seller.
To get more of a hybrid you like, root a cutting from it.
Clones and cultivars
Cuttings, pups (side shoots) and grafts all make new plants without seed, and almost always each new plant has the same genes as the one it came from. A clone is all the plants multiplied that way from a single original, however many pots it fills.
A cultivar is a selection chosen for a feature, such as flower color, that its plants share and keep when they are propagated in a way that copies the plant, such as from cuttings. Its name follows the botanical name, capitalized and in single quotes.
What PC means
PC is a clone label that growers and sellers use for the San Pedro most commonly grown in the United States. They often spell it out as "predominant cultivar", but in practice PC is used for a single clone and is written without the single quotes of a formal cultivar name. PC is not part of the botanical name.
Growers generally treat every PC plant as a cutting, or a cutting of a cutting, of the same original. Where that original came from is unclear. San Pedro grown from seed is not PC, because each seedling is a new plant with its own genes.
PC is hard to pick out by eye, because spine count and length shift with light and growing conditions. Growers who need to be sure rely on a seller's record of where the plant came from, and on its flowers once it blooms.
Saying the names aloud
Botanical Latin is a written language with no native speakers, so there is no single right way to say it. A few common guides: sound every vowel, say "ch" as "k", and say "c" before "e" as "s".
- Echinopsis: ek-in-OP-sis.
- Trichocereus: trik-oh-SEER-ee-us.
- pachanoi: pa-KAH-no-ee. The ending is a Latin possessive, "of Pachano". A. Pachano was one of the collectors of the original specimen, with the botanist J. N. Rose.
Our Trichocereus are grown and sold strictly as ornamental specimens.
Sources
Echinopsis pachanoi (Britton & Rose) H.Friedrich & G.D.Rowley. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:88444-2
Trichocereus (A.Berger) Riccob. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:289363-2
Echinopsis macrogona (Salm-Dyck) H.Friedrich & G.D.Rowley. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:132717-1
Echinopsis lageniformis (C.F.Först.) H.Friedrich & G.D.Rowley. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:132706-1
Echinopsis bridgesii Salm-Dyck. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:132612-1
Leucostele Backeb. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:297430-2
Leucostele terscheckii (J.Parm. ex Pfeiff.) Schlumpb. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77122515-1
Leucostele chiloensis (Colla) Schlumpb. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77122512-1
Echinopsis terscheckii. UA Campus Arboretum, University of Arizona. https://apps.cals.arizona.edu/arboretum/taxon.aspx?id=831
Trichocereus pachanoi Britton & Rose. International Plant Names Index. https://www.ipni.org/n/257116-2
Phylogenomics and classification of Cactaceae based on hundreds of nuclear genes. Jurriaan M. de Vos, Urs Eggli, Reto Nyffeler and others, Plant Systematics and Evolution 311: 28, 2025. https://link.springer.com/article/10.1007/s00606-025-01948-z
Cactaceae at Caryophyllales.org- A dynamic online species-level taxonomic backbone for the family. Nadja Korotkova and others, Willdenowia 51: 251-270, 2021. https://digitalcommons.fiu.edu/all_faculty/342
Identity and neotypification of Cereus macrogonus, the type species of the genus Trichocereus (Cactaceae). Sofía Albesiano and Roberto Kiesling, Haseltonia 17: 24-34, 2012. https://cactusconservation.org/wp-content/uploads/2020/03/Albesiano_Kiesling_2012_Haseltonia_17_24-34.pdf
The Nomenclature of Horticultural Plants: An Explanation. Scott Zona, Extension Gardener, NC State Extension, 2023. https://extensiongardener.ces.ncsu.edu/extension-gardener-plant-toolbox/the-nomenclature-of-horticultural-plants-an-explanation/
Propagation (chapter 13). North Carolina Extension Gardener Handbook, NC State Extension. https://content.ces.ncsu.edu/extension-gardener-handbook/13-propagation
Echinopsis. North Carolina Extension Gardener Plant Toolbox, NC State Extension. https://plants.ces.ncsu.edu/plants/echinopsis/
What's in a Name? WSU Ferry County Extension, Washington State University, 2016. https://wpcdn.web.wsu.edu/extension/uploads/sites/74/2016/03/Whats-in-a-Name-pdf.pdf
How to Pronounce Scientific Names. Aaron Steil, Iowa State University Extension and Outreach. https://yardandgarden.extension.iastate.edu/how-to/how-pronounce-scientific-names
International Code of Nomenclature for algae, fungi, and plants: Article 53, Article 60, Article H.2 and Article H.3. International Association for Plant Taxonomy. https://www.iapt-taxon.org/nomen/pages/main/art_53.html ; https://www.iapt-taxon.org/nomen/pages/main/art_60.html ; https://www.iapt-taxon.org/nomen/pages/main/art_h2.html ; https://www.iapt-taxon.org/nomen/pages/main/art_h3.html