Reference
The species
These four are the species named most often on this site. Most names in the library sit under the rest of the genus, and some are crosses. The four are told apart on four features: how many ribs, how far apart the areoles sit, what the spines do, and what the skin looks like.
A clone name is not proof of a species, and a photograph is a pointer rather than an answer.
Pachanoi
The plain green San Pedro column most people picture.
71 in the library8 grown here
Bridgesii
The slim one, with few ribs and long needle spines.
72 in the library16 grown here
Peruvianus
The stout blue one, with bigger areoles and longer spines.
29 in the library3 grown here
Scopulicola
Very few ribs, no spines, and a glossy melted-looking skin.
20 in the library1 grown here
The rest of the genus, by name
These eight are other names the trade uses. Each one is a reference page about the name itself: who published it, and what has been collected in the wild under it.
Macrogonus
The name macrogonus, and how San Pedro and peruvianus relate to it.
Terscheckii
The heavily armed giant — and, in the Caryophyllales Network's taxonomy, not a Trichocereus at all.
Validus
An old published name, and where the working taxonomy puts it today.
Cuzcoensis
The name cuzcoensis, where it has been collected, and the other names met alongside it.
Knuthianus
A published name, and the plants sold under it.
Santaensis
The name santaensis, and where it has been collected.
Spachianus
What a spachianus looks like, an old published name, and where it has been collected.
Huanucoensis
A name used in the trade.
A note on the names
Reportedly a 2012 revision reads Salm-Dyck's original description of Cereus macrogonus as the plant later named Trichocereus peruvianus, and fixes the identity by designating a neotype.
Growers have carried on using the name loosely regardless, for almost any stout, blue, well-armed column.
Macrogonus, pachanoi and peruvianus are all still in everyday use among growers.
The three that are not species
A name in one of these three is not a judgment about the plant. It is a cross, or a name that none of the four species pages above covers.
Sources
Learned from the sanpedrocact.us community wiki (CC BY-NC 4.0) and from @sanpedromastery6262 on YouTube.
Every photograph in the yard pages and the shop is of a plant grown here, except where a listing says it was grown by somebody else — it says so on the listing, above the price.
Every source behind these pages →