Hello, so you want to know more about Trichocereus Cacti, huh? Well, welcome to the right place.

I've been collecting Trichocereus for a few years now, I don't claim to be a complete expert but I have a lot of knowledge to share and I'd like to do it. I see a loooooot of repeat ID questions, as well as some common repeat general Trichocereus horticulture questions on this subreddit a lot, I'm enthusiastic to see more people finding and also getting excited about this amazing plant genus, but I am hoping a post along this nature, especially if stickied or added to the sidebar might curtail some of those repeat questions and ID requests and make more room for better discussion and content. I may add content as I think of stuff that might be useful to add-in. You can also use the comment section below to ask questions and I will get to them when I have the chance.

So to start right off I wanna break down Trichocereus Identification techniques that can help you sharpen your eye for these cacti. A lot of people ask how you can tell the difference from some of these cultivars and a lot of that just comes with time and experience.

This guide is broken up into the following sections in this order:

1. Some Common Trichocereus Look-Alikes

2. Generalized Trichocereus Growing Guide

3. Trichocereus Species-Specific Identification and Information

^{If using Reddit Enchancement Suite RES I recommend viewing with the show images button off and clicking the open image button next to each image as you go to make it easier to read but you can of course view it anyway you want.}

A pre-caution to gardeners about misidentification. There is so much diversity in this genus but there is a lot of commonalities shared between them, obviously. Hybridization blurs the lines and a lot of hybrids show traits that may not resemble either parent and may look like the offspring of an entirely different species. Examples of this being Trichocereus Peruvianus when hybridized with Trichocereus Bridgesii may come out looking more like Trichocereus Cuzcoensis than either parent. Proper labeling when growing Trichocereus is crucial, especially when starting from seed as many young cacti are indistinguishable. It is extremely bad etiquette to guess on ID and trade those cacti out. If you are not 110% sure of a cactus' genetics do not present your guess as fact, there is nothing wrong with taking your best guess but make it very clear that you are not truly sure of the ID. If I am anything less than completely certain I label as Unknown Genetics, Trichocereus. I have had to do this to maaaaany seed batches over the years as labels fade, containers get knocked over by animals or wind. It sucks but it's the right thing to do, don't go muddying up lineages and ID.

Some Common Trichocereus Look-Alikes:

Myrtillocactus Sp.

https://i.imgur.com/OivklNj.png

https://i.imgur.com/4b9GAhK.jpg

Myrtillocactus Geometrizans and the genus as a whole is sometimes mistakenly identified as Trichocereus Bridgesii due to a somewhat similar form and color. Take note of the areoles, however. The spines are more sparse than found on Trichocereus and they are much shorter than what would be found on Trichocereus Bridgesii. New Spines on Geometrizans young growth tend to be solid black, something you won't find on almost any Trichocereus though some Trichocereus spines do get very very dark red which almost appears as black. On the topic of red, mytrillocactus cochal has red and yellow spines on new growth, but they are inverted of what you would see on a Trichocereus. M. Cochal has red at the base and quickly turns yellow going outward whereas Trichocereus with red and yellow spines will usually be yellow halfway or most of the way up the spine and the ends will be red/dark red. M. Cochal spines will also all turn to white over time. A trait that is seen on many cacti including some Trichocereus.

Cereus Sp.

https://i.imgur.com/oVT6ZS7.png

https://i.imgur.com/QhXs3Gq.png

https://i.imgur.com/mMDh4xe.jpg

https://i.imgur.com/kgzUSv5.png

The Cereus genus is quite large, home to over 30 species. The most commonly found are C. Peruvianus, C. Reperandus, and C. Forbesii. They grow in a similar way to Trichocereus. Cereus like all taxonomical names is Latin, its meaning is 'Candle'. The Cacti grow in a candle-like shape, hence the name. This is why 'cereus' is found in many columnar cacti names, including Trichocereus. Trich(o)[/Thrix] meaning hairy, the name was given Trichocereus after the hairy flowers that it grows. Back to Cereus Sp. though these cacti are commonly mistaken for Trichocereus due to their shape but the main thing to pay attention to is the ribs of the cacti. They grow thin on Cereus Sp. They also level out and are flat. An extremely thirsty Trichocereus 'PC' may have recessed ribs that look similar but they will not be as flat as Cereus Sp. no matter how thirsty. Flowers buds look different and the flowers have no hairs so look for flowers to ID as well.

Pilosocereus Sp.

https://i.imgur.com/1lL9eWy.jpg

https://i.imgur.com/fd4Eawe.jpg

https://i.imgur.com/ZHVhrA7.jpg

https://i.imgur.com/wRq90iI.jpg

https://i.imgur.com/OyyA32P.jpg

https://i.imgur.com/kc5UfaL.jpg

https://i.imgur.com/fzcdDho.jpg

Okay, so Pilosocereus, take note of the name here too. Very similar to Trichocereus as Pilosocereus translates also to Hairy Candle, using a different greek word to get the same meaning. Pilosocereus is however named such due to its hairy areoles, not flowers. Some young plants may look like Trichocereus Peruvianus, especially with the chevrons (the chevrons are the 'V' shape growth marks up the cacti, marks usually produced from waxy outer layer that protects from UV.) Look for hair coming out the areoles, if it has it, it is not a Trichocereus, don't mistake hairy flower buds for bare areoles with hair. Spines on Pilosocereus Sp. tend to be yellow, long and heavily clustered. This areole growth pattern is not found on any Trichocereus Sp. There are some exceptions to the rule:

https://i.imgur.com/8tEFKQ6.jpg

The spines pictured above as well as the form look very similar to Trichocereus Peruvianus but again take note of the amount of spines, way more than you'd find on a T. Peruvianus, ID would be easier on an older plant as well.

Polaskia Chichipe

https://i.imgur.com/iqiLWJ0.jpg

https://i.imgur.com/WmrE0kP.jpg

https://i.imgur.com/g3xNwyn.jpg

https://i.imgur.com/gtWxTo3.jpg

https://i.imgur.com/3ZCMxtv.jpg

Polaskia Chichipe is a common find in your local big-box store. It looks similar to Trichocereus depending on its environment and growth stage. As they mature like all cacti they will be easier to distinguish from Trichocereus, it's mainly the little ones you gotta watch for. Most P. Chichipe have a strong waxy epidermis with heavy chevroning, the chevrons go deep and are taller than wide. Lots of spines in one areole with one central leader, usually curved at the end. New growth spines are sometimes red, sometimes not. Has a sawtooth trait similar to what is found in some Trichocereus, for example the 'PC' cultivar, ribs are usually sharper angled than Trichocereus' rounded shape.

Stetsonia Coryne

https://i.imgur.com/HKavwDH.jpg

https://i.imgur.com/qisl3Uo.jpg

https://i.imgur.com/gmIFn3Y.jpg

https://i.imgur.com/UizlqeI.jpg

The Argentine Toothpick Cactus can sometimes be mistaken as a Trichocereus Peruvianus to the untrained eye. Again, as they age they become easier and easier to distinguish but with time you should have no trouble telling the two genera apart at all stages of growth even tiny seedlings. The older spines are white, new spines are jet black, long and sharp like a toothpick. Each areole is like a nodule that protrudes outward giving the cacti a bulging appearance. The epidermis can be very similar looking to Trichocereus so it's about the shape and areoles on this one.

Pachycereus Sp.

https://i.imgur.com/MpwF5Za.png

https://i.imgur.com/yBsrze8.jpg

Pachycereus tend to be very large growing cacti. Another one that tends to only get the completely untrained eye. With some time and exposure, you should have no trouble telling the two apart. The most common mistaken species is probably P. Marginatus, though one could mistake a mature P. Pringlei for a Trichocereus Terscheckii. Take note of the areole clustering on Pachycereus, in most species the areoles also tend to be connected top to bottom with a small line of felt and make an unbreaking line all the way up the side of the plant. This genus is diverse but the commonly only two are found, P. Marginatus and P. Pringlei, you may encounter P. Weberi, P. Fulviceps and P. Schottii as well.

Trichocereus Identification Growing Guide:

(may add more species over time but these will cover the basics)

General Trichocereus Growing Tips:

Information shared here should be a universal truth to all Trichocereus species unless noted otherwise. Assuming anything written here applies to your plant if it is a Trichocereus.

Light Requirements:

Trichocereus Species require a lot of light to reach their full potential. The cacti are very enduring and can live in a wide range of light intensity, however, when grown in too dim of an area the cacti will stretch thin and grow faster in hopes to escape the shade and find brighter light. This is not ideal. Etiolated growth may not support the full weight of the plant if it returns to a normal light environment causing damage. Your cactus is also more susceptible to disease, fungus, and bacteria when starved of light. It needs the energy to support its immune system. Light will also dry out the soil which is necessary for a healthy root system.

Watering Guide Winter Care:

Your watering habits should change with the season and will depend on a lot of different factors. If you're in ground or a container, how large the container is, what type of soil your plant is in, how big your plant is, how sunny it is, how wet or dry. You should never water your cactus if the soil is already wet.

During the summer months I can get away with watering every other day outside in Southern California. If you live somewhere more wet or less sunny and hot you probably cannot get away with this much water. Wait until the soil is dry 1.5 inches down.

Drainage is also important, it is possible for the top of the soil to be dry and the bottom waterlogged. I usually check if its time to water by lifting a couple of the containers. If they feel light I water, if they're heavy I don't. If a pot seems dry but is heavy it could be the soil composition, rocks, etc or you might not have proper drainage. Make sure you have drainage holes in your container and that you are planting with perlite or vermiculite or something to add drainage throughout your mix. Runoff water should be escaping out the bottom when you're watering.

During fall depending on your zone you will do one of three things:

1. Nothing, don't water, don't move plants, let em get rained on (Zone 9B )
2. Stop watering in September, cover or move plants to area that will protect from rain and light frost. (Zone 8B-9A)
3. Stop watering in September, cover plants heavily or move plants inside or to a location that will protect from winter environment (Zone 1A - Zone 8A)

Keep doing the above respectively to your zone until Spring. at which point you should resume your normal watering schedule. Remember to allow the soil to dry out most of the way through before watering again. If your soil has become hydrophobic and is repelling water you may need to soak the container by setting it in something you can fill with water. Let it sit until it is retaining water again

Fertilizer:

Trichocereus, for the most part, enjoy having a nutrient-rich soil. You can grow these in the same soil and fertilizer schedule that you would use for common garden plants such as tomatoes, cannabis and peppers. I use General Hydroponics Maxi two-part powder fertilizer. Mixed together these two are essentially the Lucas Formula method for those familiar. Fertilize once a month or so during the growing season only.

Species-Specific Information:

Trichocereus 'PC':

https://i.imgur.com/PPKVFk5.jpg

https://i.imgur.com/DKjeJyh.jpg

https://i.imgur.com/2mZdbpC.jpg

Trichocereus PC has a debated ancestry. I am going to GUESS this is a Trichocereus Riomizquensis or Trichocereus Bridgesii x Pachanoi hybrid. Many refer to PC as being T. Pachanoi and while it does share some shape as with many plants it's the flowers that do reveal the identity. Pachanoi flowers are not covered in white hair like PC, Bridgesii and other Bolivian species are.

This cultivar is very common as it has been mass propagated for decades and is sold in big box stores, Walmart, Lowes, Home Depot and more. Which brings us to warning #2 of this guide, and my first disclaimer. I do not condone the consuming or processing of Trichocereus cacti or any cacti, this guide is for ID purposes and ornamental growing. However, for harm reduction purposes I feel compelled to mention the dangers of consuming plants grown by commercial growers, especially Altmans.

Almost all cacti in almost every chain store come from Altman's Nursery. I have nothing against the nursery though for human safety and the bee's sake I wish no company would use neonicotinoids; a systemic pesticide that can cause health issues in humans if consumed and birth defects in infants. It will persist in all parts of the plant, including new growth for about a year. The pesticide cannot be flushed out and I highly caution against using plants from commercial growers. Please do your research.

Trichocereus PC has a sawtoothed rib shape, like all cacti it is variable in shape, spines and size depending on its growing environment. The variety is capable of growing to very thick diameters on old growth. Usually, the spines are very short but occasionally on older growth, it is possible for it to send out a longer spine or two.

This cactus is very hardy, I have taken mine down to 20F with no issues. I live in a very dry area though and if it is wet the cacti will be less cold hardy. Keep the cacti dry during winter if you live in an area that will drop much below freezing (below 27F~). If you live in a more warm climate the plants can handle winter rains just fine. Depending on your elevation and sun exposure they may thin out a bit, restrict water to prevent etiolation. Cacti will go dormant when winter temps consistently get down to 40F. Expect growth to crawl to a stop at this point. If you live somewhere that has warm day temps the plant may skip dormancy regardless of the low temps. This is a particular concern if you live somewhere that experiences hard freezes around the same time as said warm days since the cacti are less cold hardy if they are not dormant. This rule applies to all cacti afaik but especially all Trichocereus.

And this is the one time in the guide that I plan to touch on the topic of alks to say yes it has them, but barely any and you should look elsewhere; and again, Home Depot, Lowes, Walmart, your grocery store, etc all get their cacti from Altmans so beware the neonicotinoids as mentioned above.

Trichocereus Pachanoi / San Pedro:

https://i.imgur.com/iAyhnnQ.png

https://i.imgur.com/MQBBMCk.jpg

Trichocereus Pachanoi are native to the Andes, a warm climate with heavy rain. These plants are resistant to rot more so than most cacti. It is more common to find split columns where the water intake exceeded the plant's capacity. Splits are usually not a life-endangering problem. Usually, they heal just fine and the plant continues growing. If your plant does split in your garden this is a sign you are using too much water and might wanna take it back a notch.

When fully mature the cactus has a very fat rounded appearance, the spines on pachanoi are usually quite short but they can and often do send out some long ones. Typically there are 5 - 7 ribs though it can grow beyond this range, only rarely. Usually, a rib count outside of this range indicates a hybrid. The areoles tend to be very small and recessed, there is typically an indented notch in the plant above each areole in a chevron shape as well. The flowers have black hairs and typically white petals with red and yellow sepals. Pollen is yellow, the plant is monoecious which means the flowers contain both male and female reproductive parts, however, the plant, as well as most cacti, are self-sterile and will require another nearby plant, human or bug to pollinate it. If pollinating your flowers you must isolate them or you have no idea what pollen might end up in there and producing seed. I guess a guide on flower isolating is in order once I'm done with this section but you can probably find something on google about the topic in the meantime.

Should be cold hardy to about 25F, more if it is really really dry. Less if it is super wet. Snow shouldn't be a problem. Might wanna cover tips with a styrofoam cup during cold snaps if you live somewhere on the edge of it's growing zone. Similarly to 'PC' this species of cacti will go dormant when winter temps consistently get down to 40F. Expect growth to crawl to a stop at this point. If you live somewhere that has warm day temps the plant may skip dormancy regardless of the low temps.

This is a particular concern if you live somewhere that experiences hard freezes around the same time as said warm days since the cacti are less cold hardy if they are not dormant. This rule applies to all cacti afaik but especially all Trichocereus.

The plant has a rich history of use throughout the last 3000 years or more, mostly for medicinal or religious use. This is the one and only San Pedro cactus. I know people like to use the name as a catch-all for trichocereus sp as a whole but it's really only the name for Trichocereus Pachanoi.

Trichocereus Bridgesii / Achuma:

https://i.imgur.com/Xswozdq.jpg

https://i.imgur.com/Wvqc7IU.jpg

https://i.imgur.com/MBUId3m.jpg

https://i.imgur.com/xvPDnRh.jpg

https://i.redd.it/21oxxyelc9k31.png

Trichocereus Bridgesii is native to Bolivia. It is typically skinnier than Trichocereus Pachanoi though there are some notable exceptions, example. cv. 'Chemical Shaman's Dick, CSD.' There are 4-8 ribs, usually though only 5-7. It is quite common to find different monstrose varieties in cultivation. There is a short form and long form monstrose variety as well as crested forms.

Bridgesii are not as hardy as Trichocereus Pachanoi, especially monstrose forms! They are also not as water tolerant or rot resistant. In my climate I can still water them the same as I do my other Trichocereus but care should be taken in more humid environments to only water when the soil is completely dry and to water the soil not the cactus body. I would also recommend that you take greater care to protect from hard freezes. Sustained freezing temperatures will kill this variety once the cold penetrates too deep its a goner and will turn to limp mush. The overwinter guide I wrote above should accomodate your bridgesii fine but I based this off a southern california climate, results may be different for growers in a more wet climate like florida though I doubt freezes are too big of a concern in Florida... I wouldn't let this plant get below 25F and I would cover the tips with a styrofoam cup if temps drop below 28F.

During fall depending on your zone you will do one of three things:

1. Nothing, don't water, don't move plants, let em get rained on (Zone 9B )
2. Stop watering in September, cover or move plants to area that will protect from rain and light frost. (Zone 8B-9A)
3. Stop watering in September, cover plants heavily or move plants inside or to a location that will protect from winter environment (Zone 1A - Zone 8A)

Trichocereus Bridgesii are also known to go spineless on older growth which makes them very easy to handle. Like Trichocereus Pachanoi, Bridgesii is also monoecious, which again means it has both male and female anatomy in one flower but it also is self sterile and will need another closely related species to pollinate it. The colloquial name for this species is Achuma. It is personally my favorite species of the genus.

Trichocereus Peruvianus:

Trichocereus Terscheckii:

Trichocereus Scopulicola:

Trichocereus Cuzcoensis:

Trichocereus Spachianus:

Trichocereus Grandiflorus:

Trichocereus Candicans: