Frank's sedge confusion

So, about a year ago I heard about this Carex frankii lookalike that I had never heard of - Carex aureolensis. It apparently has relatively recently been split out from Carex frankii and is recognized as distinct on iNaturalist. See:

Since Franks sedge was one of the first Carex species I learned to sight ID, I just assumed it was more common. But literally every time I have found a specimen that I initially think is Frank’s sedge, it turns out to be C. aureolensis.

Now I’m doubting whether or not I’ve actually ever seen Frank’s sedge in real life in Texas.

But based on the greater amount of observations of the two species in Texas, my experience with C. aureolensis being more common seems to be abnormal. Or are they just chronically mixed up? A lot of the observations of C. frankii don’t seem to have sufficient data to distinguish the two, but I hesitate to down vote identifications since I’m not even sure I know what franks sedge looks like any more since I don’t think I’ve ever seen it.

Are there any Texas wetland people or Carex spp. gurus who can speak to this?

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Are they both in the same sedge section? Can we merge them back into one species? It doesn’t do inat any favors if they can’t be told apart.

I’m not finding much for sources that map Carex frankii in Texas when they also accept C. aureolensis. C. frankii isn’t mapped in Texas in Flora of North America or Weakley 2018. USDA PLANTS and BONAP map it in Texas, but BONAP excludes C. aureolensis completely and USDA PLANTS only shows state-distribution (not counties) for C. aureolensis, which makes me think their assessment is incomplete and that they are both treating C. frankii sensu lato. iNaturalist is following Plants of the World Online, which is in agreement with FNA and Weakley that C. aureolensis is a Real Thing, so C. frankii is sensu stricto here.

As far as identification, I know Justin would not mind me sharing these here:

From his blog:

Thingamabob Carex aureolensis Carex frankii
Pistillate scales Broader, with translucent body, up to 1.1 mm wide Narrow, up to 0.4 mm wide
Staminate scales Lanceolate to ovate, up to 1.6 mm wide, close-packed linear, up to 0.8 mm wide, tips spreading
Number of perigynia Up to 80 per spike Up to 100 per spike
Perigynium beak Up to 2.0 mm long Up to 2.5 mm long
Growth habit Forms big colonies with long rhizomes Forms loose clumps with short rhizomes

Not helpful for the majority of iNat observations, which might just show a single culm, but in cases it’s not clear you can always feel fine bumping back to section (Carex sect. Squarrosae) if that’s all the evidence provides. Bumping back to section will also help the computer vision learn not to be as “confident” that these southern Squarrosae are C. frankii vs. C. aureolensis.

All with the big caveat that I’ve never seen C. aureolensis. Just wanted to learn a thing by putting this together. :)


this is the explanation from Botanical Research Institute of Texas (BRIT) in its Illustrated Flora of East Texas ( Ford and Reznicek (2002) designated all TX material of this species as C. aureolensis Steud., while previous modern floras have treated C. aureolensis as a synonym of C. frankii. Ford and Reznicek (2002) stated that C. aureolensis “has been recognized as a distinct species based on its staminate and pistillate scale morphology, growth habit, and distribution.” However, TX material possibly consists of two distinct taxa. Until more detailed study of this complex in TX is carried out and to avoid confusion, for the present we are continuing to use the name C. frankii for TX material. Section Squarrosae

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Bouteloua, I want to thank you just for posting this blog. Funniest thing I’ve read all month. Also loving “thingamabob” as a column header in that table.

I live outside of the USDA range of C. aureolensis, but here in western NY state I just encountered Frank’s Sedge for the first time last week. Up here it’s an S2 endangered species, though this newly observed population may more than double its known numbers in the state. I’m sure that, just for fun, I’ll be checking those pistillate scales sometime to confirm the obvious result that this NY population is not aureolensis.


@charlie I think that when you know what you’re looking for it, the distinction between the two species is pretty obvious if you know that C. aureolensis exists as distinct from Frank’s sedge. That’s not so different a case from many other genera either. So, I don’t think I would advocate for a merging of the two species.

I think the issue is just that people don’t even realize that there’s a distinction that has to be made. In my wetland/botany classes in college ‘Franks sedge’ was one of the first things TAs or professors would point out and we’d learn to sight ID it pretty easily. In hind sight, I doubt anything we were taught as Frank’s sedge in Texas was actually anything but C. aureolensis. But I didn’t know that, so I never saw any need to get down to the nitty gritty of what characteristics makes Frank’s sedge distinct - I’d see something matching the general form and unquestioningly note it as C. frankii.

I think that same mentality is potentially contributing to a lot of incorrect IDs in Texas of C. aureolensis as frankii. People see the form and automatically agree with it.

I guess there’s a lot of bumping back to section to be done? I may also message @anewman and @eric-keith to get their thoughts. Both of them are the sedge kings in Texas. A lot of people (myself included) tend to implicitly accept their IDs.


On the basis of the two photos aureolensis seems to have pistillate scales with two small auricles at awn base which are missing in frankii, it is always so?

Huh? Charlie you must be an ecologist, yes? I hope the comment was made in jest because, if not, your sentiment offends me, rather. It’s just bad science to lump them because you are unable to tell them apart. How does it do iNat any favours to disregard a valid taxon and willfully misidentify it?

huh what? you’re offended by the questioning of excessive splitting? Are we not allowed to question the splitters now?

But seriously, it isn’t bad science to identify something to section if you can’t identify it to species, it’s bad science the other way around. It’s never bad science to apply a higher taxonomic order if you aren’t sure. If some people can actually tell them apart, yeah, it’s fine to keep the species in the database if they are valid species and leave the section for those who can’t…

unfortunately, good luck drawing a reasonable line as to what a ‘valid’ species is, with splitters around.

No, agreed, IDing to section is what should happen if sympatric taxa are indistinguishable in the absence of diagnostic images. This is far more of a problem for the entomologists who are used to not being able to ID to species level. I thought you were advocating merging C. aureolensis with C. frankii because they are so visually similar.

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well, i might advocate that if they aren’t consistently different, but that isn’t something we can do unilaterally on iNat anyhow. And it sounds like they are actually different.

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Yeah, that’s the case. Additionally there’s supposed to be a difference in growth form where aureolensis is rhizomatous and Frank’s sedge is cespitose

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