Opuntia Phaeacantha taxonomy

I was just out and about documenting some Phaeacantha for my area on account of there not being much documented, and I noticed something interesting. There appears to be two varieties of Phaeacantha in this area, and I’m not sure if this is unique to this area or if it’s known elsewhere.

There is the usual Brown Spined Prickly Pear, as seen here, then there is this one. Longer, more oval shaped pads, with fewer spines and little to no glochids. It looks quite similar to the Polyacantha, but much larger.

Is this a well known variety, or maybe a species mislabed by the preserve owners? Or, probably less likely, a Phaeacantha x Polyacantha hybrid? I’m probably just stupid, and overthinking this.


You might try flagging the taxon on the iNaturalist taxon page and see if any curators have an opinion.

1 Like

Seems like flagging is more for incorrect taxons, but I can check. I don’t think iNaturalist is wrong here, I’m just not sure the preserve I went to is right about the second one being Phaeacantha, it looks quite different from most every other Phaeacantha I see documented here and elsewhere online. I might be totally wrong though.

They might be two different species. Labeling is not 100% dependable. If you have them posted as separate observations on iNaturalist, you could try tagging @davidferguson or another frequent identifier of Opuntia in comments on the observation, and see if he can help.


Hi, I got tagged. I’ll try to help. One thing that is always important is to give the location (even if not exact, knowing the area the photos were taken is helpful). It often makes a huge difference in helping with identifying. Until there is more to go on, a couple of the identifications will remain tentative.

Based on the photos I’m going to guess that you took the photos somewhere on the Colorado Plateaus (perhaps e. Utah or w. Colorado)? If so, there are a number of species present in the region, though several of them do not often appear in plant guides or floras. It is confusing when a book only lists two or three species and there are really perhaps six or eight present in a given area, but this is generally the case. It is often resolved in people’s minds by calling everything “hybrids”. Hybrids do occur, but they are not particularly common.

The first photo is of Opuntia tortispina. The flowers, juicy fruits, and seeds are similar to those of O. phaeacantha, but it is generally a smaller plant with areoles closer together, and usually appears spinier (often not because there are more spines, but because they are closer together). On the Colorado Plateaus, the flower color is highly variable, so isn’t much help in idenfication (the stigma lobes are green though, where they are varied in color, but often pale whitish or yellowish in O. phaeacantha).

The second is difficult to tell, it looks like a plant that grows in shade most of the day. It also looks like there is a broken beer bottle bottom behind the plant, which gives some potential size reference (a largish plant for the region - if I guessed correctly). I would need to see the flowers, fruits, and ideally new growth (with leaves still on) to be certain, but my best guesses would be O. woodsii, O. gilvescens or O. phaeacantha. Based on what I can see here, I think O. woodsii is most likely, but more information could change my mind. Flower color won’t help much here, but the structure of the flower can. As for color, O. woodsii is usually orange, pink, or red, while the other two are usually yellow (O. phaeacantha often with an orange or red center, but gilvescens rarely). O. gilvescens usually has rounder pads than this, and phaeacantha usually somewhat wider pads with more and longer spines. O. woodsii will have mostly largish elongate fruit. O. phaeacantha will have smaller fruits than the other two - simlar to those of O. tortispina (but probably larger than those), roughly barrel-shaped, and O. gilvescens will usually have largish broad fruits. All relative though - they will all have fruit smaller than some of the bigger more southern species. It may not be any of these species though - there are other options, but none seem to fit your photo very well.

The third photo is probably Opuntia polyacantha (though the fruit still present looks abnormal - like it dried out before mature - so it doesn’t help much - it could be a hybrid). It appears to be of a variety of O. polyacantha found on the Colorado Plateaus mostly in Colorado and Utah (leaking into Wyoming and Arizona a tiny bit), and also in desert areas of the northern Great Basin in Utah, Idaho, and Nevada. This plant has been given a few names, the oldest of which is Opuntia rhodantha (another is Opuntia xanthostemma, based on a different flower color). O. [polyacantha var.] rhodantha has never “legally” been made a variety of O. polyacantha, but that’s what it is. In Lyman Benson’s books, this sort was lumped in with the rather similar variety “utahensis” under the “species” O. erinacea. O. erinacea is a VERY different plant, and also belongs with O. polyacantha. The name erinacea has “legally” been made a variety of O. polyacantha, but the other two names didn’t tag along when that was done. So, it’s basically a matter of book-keeping; the names need to basically be filed correctly under O. polyacantha, following the botanical code, be “legal”, even if they are the correct names. So, biologically this looks like “rhodantha”; a variant of the O. polyacantha group that is commonly grown in gardens where winters are cold. AND, I could be totally wrong - it could be O. polyacantha crossed with something else (such as O. tortispina).

Sorry, I tend to be long-winded sometimes.

Hope that helps. I know it’s a little wishy-washy at this point.

If you have more photos, and if you can tell us where they were found, that would help to be a little more certain.



Thank you, that is a very detailed response, much more than I was expecting. It’s really quite helpful.

The species were found in Hawkins Preserve in Cortez, Colorado. They only list Polyacantha and Phaeacantha as species there.

It is in a little rock crevice, so it might be somewhat etiolated, but the other species were also fairly long and oval shaped, even with proper sun exposure. It is fairly large, although low growing, some plants were upwards of 2-2 1/2 feet tall. Unfortunately I don’t have any flowers or new growth buds or anything, these photos were all taken recently.

Here is just a photo dump of the random shots I took whilst hiking, if that helps at all.

1 Like

Welcome @southwesternsol. It looks like you’ve started to add some Opuntia photos as observations on iNat, which is great. The main iNat interface is much better suited to helping bring people together around identification than the forums. You’re welcome to tag @davidferguson or other experienced Opuntia identifiers to draw their attention, but people will find your observations anyhow in time. Over time more observations with more accurate IDs adds up to a more accurate picture of distribution for these species.

EDIT: One more thing… Of course, it’s always a challenge to accurately ID plants when they’re not flowering, so it could be that a clearer picture will emerge if you’re able to add some observations of flowering Opuntia in the spring.


That’s why I went out and took these photos the other day. I wanted to get some before it got cold and they started going dormant. I can check in again next spring and/or early summer for flowers.

1 Like

After taking some time to look up and read a bit about the various species suggested, I do agree that this really does look like O. Woodsii. The only problem is I don’t see established range on the Colorado Plateau. But that might just be that it’s a lesser known species and not as well documented. Otherwise, that looks accurate to me.

A comparison of another one I found, and O. Woodsii from opuntiads.com

As @rupertclayton already mentioned, identification and commentary on specific observations should be done on individual iNaturalist observations, instead of here on the Forum, which is for more general topics related to iNaturalist. So I’m going to go ahead and close this thread to help redirect the discussion to the observations.

@southwesternsol I would encourage you to post the images you linked here as more iNat observations, and solicit expert help from there, using the comments. You can identify them initially as just the genus Opuntia to start the process – no need to have the species ID first. This thread can still be referenced as a link, or comments copied to relevant observations, as needed.

1 Like