Friday, December 11, 2009

Cactus Blindness: Its Causes and Treatment

It's time to admit my shameful secret: I have cactus blindness.

Cactus blindness is one of a number of widespread horticultural learning deficiencies (HLD), resembling (and often overlapping with) other HLDs like fern blindness, shrub blindness (I am also considerably shrub-blind, by the way), and palm blindness. Afflicted individuals are easily able to learn and recall names of different cactus species, but are unable to visually distinguish cacti well enough to apply the names accurately to plant specimens.

Ferocactus latispinus? Not particularly confident, but I didn't see much that was particularly close. Flat, yellow, curved spines don't happen a lot. UPDATE: There appears to be consensus that this is in fact Ferocactus latispinus.

Many causes have been proposed for HLDs, ranging from the socioeconomic (lack of exposure to, or accurate identification of, enough plant species in childhood) to the organic (HLDs sometimes occur following stroke or brain injury in previously unaffected individuals). Though below-average intelligence and sensory impairment may also lead to the inability to distinguish cactus species from one another, persons with these conditions are specifically excluded from the DSM-IV definition of cactus blindness, as they lead to much broader difficulties.

Cactus blindness is also distinct from the condition called cactus alexia: in the latter, species are easily distinguished, but the patient experiences great difficulty in learning the names that go with the plants.

I originally suspected this of being a Pachycereus pringlei, and then for some reason decided that it couldn't be, so I switched to Carnegiea gigantea. Carnegiea is fairly common in cultivation (easy to grow from seed), but it's also incredibly slow-growing, which means that it should cost more than these did. So now I'm leaning back toward Pachycereus pringlei. UPDATE: Could go either way, but the smart money appears to be on Carnegiea gigantea.

I bring this up first of all because of Karen715's brave admission a couple weeks ago that she, too, suffers from cactus blindness. Her courage has given me the strength to admit that I, too, find it extremely difficult to identify many of the specimens I encounter. (It is my hope that we can start a support group or something.)

Stenocereus thurberi. Not particularly certain about this, but it does match: newest spines are dark and become lighter, plus the dark areoles -- if it isn't Stenocactus thurberi, it's something that's fairly indistinguishable from it. Also I kind of want this now. UPDATE: Does in fact appear to be Stenocereus thurberi. Yay me.

Secondly, I recently went back to my former workplace and photographed a few cacti there (bought a couple, too, alas), thinking I could identify them easily and then use the photos for yearbook pictures, and I think I even actually did, with great difficulty and the assistance of the photos at, identify a couple of them. However, some of them continued to stump me, either because none of the 1257 species represented at looked like the plant in question, or because far too many of them did for me to be able to pick one. (Some of the more questionable photos I took are decorating this post; I welcome any ID verifications or suggestions anybody wants to throw at me.)

Pachycereus marginatus. I'm just, you know, damn positive that I've got a P. marginatus this time. I had previously reported buying a P. marginatus, which for some reason I really really wanted, but I now think that that plant is probably an Isolatocereus dumortieri instead. So now I have this, which I really think probably is a Pachycereus marginatus. UPDATE: Experts agree.

Treatment of cactus blindness typically falls into one of three types. In conventional cactus blindness therapy (CCBT), CB sufferers are encouraged, with the aid of worksheets, photographs, and (when possible) actual cactus specimens, to describe plants in minute detail, with the aim of training the individual to notice the small distinctions between species. This is essentially the training of afflicted individuals to become cactus taxonomists, and while it has a high success rate (about 80% of subjects will become able to identify at least 100 cactus species with at least 70% accuracy), it also takes a considerable amount of time, and requires the assistance of a qualified trainer at all times. Consequently, it is very expensive, and CCBT-certified trainers may not be found in all areas, though cases are known of people who have taught themselves to overcome cactus blindness through informal CCBT-like methods.

Was tagged as "Lemaireocerous." They probably meant Lemaireocereus, though that still doesn't help, since the genus is now obsolete, and the species in it were distributed across five or six other genera. None of the pictures within those genera at resemble this as far as I'm concerned, and of course we have no real guarantee that Lemaireocereus was the right ID to begin with. UPDATE: I lean toward the suggestion of Browningia hertlingiana (see comments).

The other treatment approach is known as wholistic cactus blindness therapy, or WCBT. WCBT de-emphasizes verbalization of the distinctions between species and instead focuses its efforts on the subconscious: subjects are presented, repeatedly, with randomized pairs of photos or specimens of cacti, and asked to identify whether they are the same species or different species. This, it is said, trains the mind to identify the relevant details which distinguish one species from another, without the tedious completion of worksheets as in CCBT. WCBT is also easily adapted to computer software, making it considerably more affordable and accessible than other therapies. Critics of WCBT point out that it does little to link the image of a particular cactus species to a species name, and is therefore not particularly useful in fostering cactus-related communication. Many WCBT trainers have responded to this charge by adding an additional four-week program to the end of a course of WCBT specifically for the purpose of linking names to the now-mentally-distinct species in the subject's mind.

NOID cactus #2. Lots of stuff looks sort of like this, but the arrangement of the spines (short ones pointing up, left, and right, plus a long one pointing down) seems like it's trying very hard to mean something. I couldn't find a match, and wasted a really ridiculous amount of time trying. UPDATE: I kind of lean toward Mammillaria winterae, though to be safe I think I'll just go with "Mammillaria sp."

Incremental cactus blindness therapy (ICBT), the newest of the CB therapies to gain acceptance, focuses on learning the distinguishing characteristics of only the most commonly-sold or -observed cacti, and those with the most distinctive appearances (e.g. Astrophytum myriostigma, which is fairly hard to confuse with anything else), slowly expanding the pool of one's knowledge only once the initial easy group have been mastered. Its largest advantage over the other methods is that it is more immediately useful than either CCBT or WCBT, enabling the subject to identify several commonly-encountered cactus species after the very first therapeutic session. ICBT is also somewhat adaptable to computer software and requires considerably less of a therapist than CCBT, making it less expensive and easily available. The main disadvantage of ICBT is that accidental exposure to unknown cactus species can result in the mental assignment of mistaken identities, which are frequently difficult to unlearn later on. ICBT also has a rather steep learning curve, which subjects often find discouraging, leading to a dropout rate more than double that of CCBT or WCBT.

To the best of my knowledge, the above therapies have not been attempted with other varieties of HLDs.

NOID cactus #1. This one makes me kind of crazy: I see it for sale all the time, so you'd think it would be easy to find out what it is, but no. I found plenty of approximate visual matches at, but nothing I could be positive about. UPDATE: Appears to be Parodia leninghausii.

Personally, I'm working a combination of CCBT and ICBT, on my own, with only the internet to guide me, and if I manage to learn anything I'll let you know. Meanwhile, perhaps we should be looking for some available church basements, or setting up a dedicated CB blog, or something. Who's in?

Mammillaria spinosissima. I'm actually pretty confident about this ID; the coloration is pretty distinctive, and I know it's a fairly popular species ("red-headed Irishman cactus"). (UPDATE: Experts agree.) This is one of the two I went ahead and purchased.

UPDATE: Enormous thanks to Daiv Freeman, Peter Breslin, erin, and CelticRose, for their help and suggestions on the NOIDs in this post, and confirmations on the ones I thought I had right.

Totally skippable political correctness disclaimer and commentary:

I'm not trying to imply that actual learning disabilities aren't real or shouldn't be taken seriously. They of course are, and should. The targets of ridicule here are more the non-disabled people who patronizingly claim every little obstacle's defeat as being inspiring and courageous than for the people who actually have the disabilities, people who try to make unchosen conditions into something shameful, and my own very real difficulty in distinguishing cacti from one another.

Sometimes overcoming disability / adversity / tragedy actually is courageous, of course, but sometimes one never really gets a choice about whether or not to overcome, and in any case it's kind of a weird thing to take someone who has an unusual life situation and single them out as being even more unusual by waxing poetic about their courage and whatever.

As far as it goes, I also don't mean to suggest that the blind are more disabled than others, by using the word "blindness" as part of the term for my made-up condition. It seemed like a better metaphor than, say, deafness, because people generally look at cacti a lot more than they listen to them.

As I have alluded to before, I don't want PATSP to be accidentally offensive to anybody, of whatever age, gender identity, sexual orientation, degree of disability, country of origin or residence, race, mental illness, etc. I want as much of the offensiveness as possible to be on purpose. At the same time, pretty much any reference to certain of these topics is going to be offensive to somebody, however it's phrased, because minority communities don't ever necessarily agree unanimously on PC language, reclaiming slurs, etc. (There's not even total agreement on whether "the disabled" exist as a group, or, if they do, exactly who belongs in it.) So I figure my choices are to never mention these people at all, effectively "disappearing" minority groups into nonexistence, or mention and try to make clear that I'm doing the best I can not to piss people off through my own privilege as a white, able-bodied, cisgendered, American male. (I've been noticing lately that I tend to assume my readers are U.S. or Canadian residents, in a way which probably marginalizes readers from other countries, and have been trying to think of ways to make that happen less often.) I do actually try to think about these things. Sometimes I don't think hard enough.

If I have expressed myself in a particularly inelegant or ignorant way on the matter, please let me know.


Ginny Burton said...

Great post! Let us know when you get your non-profit status and post a little "Donate" button from Paypal.

erin said...

It's good to know I'm not alone! I never noticed my CB until I brought some cacti home last year and realized I could not figure out what they were. One of them looks like the one you call Lemaireocereus. I had been calling it Trichocereus peruvianus, but with only moderate confidence. Check it out.

our friend Ben said...

Another classic post, Mr. S.! My very first houseplants were cacti---the first cactus dish I made, in sixth grade, remained a cherished treasure until some drunken college roommates smashed it---and being me, I of course bought as many books about cacti as cacti themselves. But alas, taxonomy is such a slippery science. I still love cacti and succulents and grow them with delight, but, as with orchids and perennials, it seems that you can't take a nap without the nomenclature being entirely rearranged. Guess I'd better start trying to get back in the game. Sigh...

Peter Breslin said...

Hi! Funny post! I suffer from the opposite of Cactus Blindness, which would be Annoying-Everyone-By-Insisting-To-Know-Not-Only- Species-But-Also-Subspecies-and Taxonomical-History-itis.

I have many friends to whom all cacti literally look alike, include succulents that are not cacti and even sometimes fenceposts, small furry mammals and certain rocks and minerals.

anyway...I think the "Lemaireocereus" is a Pilocereus, but I'm terrible with columnar cacti so I'm not sure.

Your frustrating fuzzy gold no ID is Parodia (Notocactus) leninghausii.

The other no ID with the tubercles and downward pointing spines remains a mystery to me as well.

You guesses on F. latispinus, C. gigantea, S. thurberi and M. spino. seem spot on to me.

Maybe you don't really suffer from CB after all?

One of your readers sent the link to cactiGuide so I'm sure you are about to be inundated with other suggestions any minute....


CelticRose said...

ROTFLOL! Great post Mr. S!

Thanks for mentioning I've just posted a link to this blog on the forum over there and encouraged them to help you identify your plants.

You are not alone in your inability to tell cacti apart. Cacti are HARD! They hybridize easily, for one thing. Put two closely related cacti together, and pretty soon you'll have a third species. Also, no one can agree on a single system of nomenclature, and the nomenclature keeps changing!

Don't feel bad: I grew up in the Arizona Desert, and until about a year ago I didn't know the difference between most cacti. I knew there were saguaros, prickly pears, and chollas. I didn't even know there were different species of prickly pears and chollas! lol I'm still very much a beginner when it comes to cacti; the learning curve is HUGE.

Hint: look very closely at the spines.

Your first pic looks like a Ferocactus of some sort.

The second pic is definitely not a saguaro. Saguaros have shortish black spines. Other than that, I have no clue what this one is.

NOID cactus #2 looks like a Mammillaria of some sort. There are over 200 different species of Mammillarias, so don't feel bad if you can't identify any but the most common ones.

Of course, rather than attempting the "therapies" outlined in this post, you can take the easy way out and simply post a picture of your unidentified cacti on the CactiGuide forum. Within a day you'll have a positive ID of your cacti. Unless you have a tricky species that can't be identified until it flowers, lol.

Karen715 said...

I'm in. Once we find a suitable basement in which to meet, (preferably one with a fluorescent light set up where we can overwinter our cacti)perhaps we can recite the following at our meetings:

"May we be granted the serenity to accept that the nomenclature will change, the courage to learn the names anyway, and the wisdom to learn the differences (among the various genera)."

By the way, in addition to being both cactus and palm blind, I am also fern- and conifer-impaired. I am learning how to recognize these, but it is a slowly process, fraught with setbacks.

mr_subjunctive said...

our friend Ben:

Well it's not like I care that much if they want to change the name; I can look up synonyms. I just want to have some kind of handle on what they are.

I mean, the name changes don't help, but they're not my main issue. Until somewhat recently, I'd never even looked closely enough at them to notice any of the details, you know?

peter breslin:

No, I'm pretty sure I have CB. That I was able to come up with some plausible guesses for some of the NOIDs, after considerable hours spent with the files, only demonstrates that I am obsessive and stubborn, not that I don't have CB.

I'd thought maybe Parodia leninghausii for the yellowish one at one point, but wasn't sure enough about it to make the guess public.


I'd found a few Mammillarias at that looked like NOID #2, but the ones with the right spines didn't have the right stem texture, and vice-versa.

I do wish that's search feature enabled searching by abundance: if I could have searched only the plants that were tagged as commonly cultivated worldwide, it would have made life a bit easier. The odds are pretty slim that I'm going to see any of the really unusual stuff at the garden center.

mr_subjunctive said...


Oh! I like that serenity prayer.

Luke said...

I suppose I would be Cactus Blind if I ever made it a point to be around Cacti (doesn't happen often here in the Pacific Northwest). More embarrassing for me is Fern Blindness; I live in fern heaven for god's sake! Why can't I keep them straight!? What kind of botanist/gardener am I!? I've never told anyone before. Oh, it feels good to share like this.

Daiv Freeman said...

Peterb said:
“You guesses on F. latispinus, C. gigantea, S. thurberi and M. spino. seem spot on to me.”

I agree with him.

I also would go with P. marginatus. The “Lemaireocereus” looks a lot like a Browningia hertlingiana, but that one is hardly common. The spines are not what I would expect, but even so Cereus peruvianus monstrose is ultimately what I think that one is.

I think NOID 2 is a problem because it is etiolated and bloated (typical garden center condition). M. polythele comes to mind as does M. spinossissma v. ‘un pico’.

Anyway, this is a fun post and I enjoyed reading it. Very glad that you’ve got some use out of Keep coming back as I am continually working on it. That search-by-encourterability feature that you mentioned is just around the corner. I’ve already started working on the code for it. It is part of an ‘advanced search’ page that will enable a user to narrow searches by multiple factors – such as flower color, habit, and encounterability all at once or one at a time.

Also, check the CSSA for a list of local CSS clubs. They are a really great way to go! And of course, you or your readers are always welcome over on the CactiForum at if you get stumped on a plant. Just post it on the forum and we’ll do our best.

Best wishes!


Joseph said...

I confess I am cactus blind as well: But it is a defensive, intentional cactus blindness. Once I start learning plant names, I start buying plants (and even worse, BREEDING plants, which means hundreds of seedlings everywhere) and I can't afford a cactus addiction right now. I'm even more vigorous in maintaining my Self Induced State of Orchid Ignorance. Once I finish grad school and get a real job, I plan to sit back and let cactus mania set in.

Ivynettle said...

I think cactus blindness is the only HDL I have... OK, and a mild case of Outdoor Fern Blindness (Dryopteris filix-mas and Athyrium filix-femina frustrated me no end when studying for one of my perennials tests).
But that's probably because I have absolutely no interest in succulents in general, and in cacti in particular. Still grumpy about my swollen, painful fingers after accidentally putting my hand in one of my parents' cacti when I was twelve. ;) (Lesson learned: Don't try to whittle in the vicinity of cacti.)

Tigerdawn said...

Because of your little disclaimer, I have learned a new function of my web browser: the Zoom! And it's very refreshing to come across someone who feels like you do. My DH is legally blind and is an Assistant DA. Everyone always is so impressed at all he's accomplished since he's blind but he wants to be judged as a Human, not a Blind.

Plowing Through Life (Martha) said...

Oh many others. I guess it's safe to come out of the cactus closet. I suffer from this as well. Terribly. And I've attempted to overcome this with ICBT, but it's been 20 years and I'm no better. Perhaps a support group is where I belong. Where do I sign up?

mr_subjunctive said...


I can imagine. Ferns aren't as problematic for me, because there aren't that many that are usually cultivated indoors, but I've no doubt it's tough outdoors, where you are.

Daiv Freeman:

Is there more than one kind of monstrose Cereus peruvianus? 'Cause the "Lemaireocereus" doesn't look at all like the ones I know (no multiple growing tips, spines much longer than I'm accustomed to).

After looking up the Browningia hertlingiana, and especially after seeing this picture (but also this one) at, I'm inclined to go with Browningia: it's not unheard of for the supplier in question to have sent stuff that was a little out of the ordinary, particularly in assortments like I'm guessing this probably was. Also a lot of the details match up (swellings around the areoles, swelling more prominent at the top of the plant than the bottom, spines both light and dark in no particular pattern from the same areole, spines both long and short from the same areole, bluish color of stem, the little straight-line indentation between areoles, etc.). Some of those would also work for a C. peruvianus, but a lot of them wouldn't.

If it is a Browningia, and they still have it, should I buy it?

I'm a little baffled by the suggestions for NOID #2: Mammillaria spinosissima 'Un Pico' has the right coloration, but all the pictures I found showed one spine per areole, not four, including the ones at CG. M. polythele seems more likely, but I'm not convinced.

It might be that the plant in question has been mistreated, but it's not hugely likely: all the plants in the post were fresh off the delivery truck as of either early September or early November.

Is Mammillaria winterae out of the question? I see this picture at (as well as the picture at has four spines per areole, and although it's not uniform across the plant, there are sections that have the three-short, one-long arrangement as my NOID.


I definitely did that with orchids, too, when I started working in the greenhouse. But then, with orchids, it's pretty nearly impossible to tell what you've got without a bloom.

Fortunately, they were almost always tagged. But I remember making a sort of point of not getting any more involved with them than just admiring the flowers. Orchids look like they would be a really expensive addiction to have.

mr_subjunctive said...


Yeah, I still have a grudge against the entire Opuntia genus from an incident when I was like five years old, so I can imagine.

What I can't imagine is going without succulents and cacti at all. Not even a Haworthia?


Speaking of which, I know the site is not as accessible to people with some disabilities as I'd like; I forget where it was, but somewhere on-line, there's a site where you type in your URL, and it locates your blog and marks it up with various suggestions for making it more useful to the disabled (including transcripts after videos, for the deaf; supplying a brief description of pictures, etc.). PATSP mostly got criticized for something about links, but I don't remember why linking was bad or what I was supposed to do differently. I assumed I'd find the site again at some point, and of course then I forgot how to find it again.

Part of what's made me think about all this is because I've seen criticism on-line of the way the show "Glee" handles its character in a wheelchair. I like the show, and I don't think they're doing as bad of a job with the wheelchair thing as they could (it sort of depends on what they intend to do with the character later on: there were indications that possibly he'd get a love interest, but so far we've only had the Very Special Wheelchair Episode).

The essay that started (or re-ignited, to be more accurate) all this thinking is here.

Water Roots:

ICBT didn't help at all?

I guess I'll give you a call when we've got a basement ready.

Ivynettle said...

"Yeah, I still have a grudge against the entire Opuntia genus from an incident when I was like five years old, so I can imagine.

What I can't imagine is going without succulents and cacti at all. Not even a Haworthia?"

Don't remind me of Opuntias - we had one at work, belonging to the boss, so cutting it back was not allowed, too heavy to move, hanging across the aisle so we had to duck under it...

Haworthias are kind of pretty, as are some Echeverias and Aloes, but as long as my living situation is as it is now (a single room with a north-facing window) I don't have room for them and couldn't keep them happy, either. And in any case, I prefer the "jungle look".

Paul said...

Orchids look like they would be a really expensive addiction to have.

But ooohh so satisfying! :D

Chelydra said...

And here I thought cactus blindness was caused by the Blind Prickly-Pear, Opuntia rufida, whose glochids are so easily detached that they are rumored to blow right off the plant into the eyes of cattle grazing nearby.

Daiv said...

Hi again. The Browningia is a possibility for sure -especially with those spines. However, small columnars can be unbelievably deceiving. Your plant appears to be in a 3 or 4 inch pot. When that thing hits 3 or 4 feet in height, the spines are going to appear a lot different in relation to the stem. You'll have to watch it as it gets bigger although I'm sure it will turn out to be one of those two.

For Noid Mamm, I gave a couple of names that popped into mind, but certainly don't insist on it. On the forum, we found it is really helpful to just toss out suggestions for a name. Then others can comment as to why they think the suggestion may or may not be right. The owner of the plant has a big advantage over those looking at a 2d picture. For reasons you mentioned, 'un pico' is out. M. winterae is a possibility, I'd suggest also M. magnimamma. A flower would make all the difference. Nice thing about Mamms is they flower easily. I would maintain that this plant was grown quite "soft" (maybe not mistreated, but treated too well?) and this make the ID more difficult to obtain.

Tigerdawn said...

I can't speak for people with disabilities but my husband at least tries very hard to make himself prepared. He has programs on the computer to blow the screen up really big and also to read out loud to him. He has had trouble with things like smartphones not being accessible and that is frustrating. Usually when companies are made aware that their product could be good for the disabled but isn't, they try to correct it. For instance, this summer Kindle is coming out with some really cool ways to be more acessible to the disabled. The Kindle is already opening DH up to a whole new world of books that he's never had access to before. Up until now he could only read books that were abridged on tape or books that the Library For The Blind converted. He wouldn't ever go in bookstores because it depressed him so much. But now he has access to any book you can put on the Kindle. Pretty cool. The technology age is making disabilities like my husband's much easier to live with. But like I said- that's just a partially blind guy's take on things. And only my paraphrase of what he's told me.

Zach said...

I really enjoy your creative posts, like this one. I lack the courage to write something like this. I think I fear that no one would read it and then I would think that it was no good. :)

Anyway, well done, lad! You have found a great outlet for your skill with the written word and your natural creative tendencies.

Jenn said...

Carnegiea gigantea.

That is DEFINITELY a saguaro. They have that distinctive base to their spines.

Compare with the base of the spines on this mature plant:

Anonymous said...

Your ferrocactus reminds me of
Echinocactus texensis (horse crippler).
I have no idea how common it is in
horticulture though.