Croton list of Central and North Central Texas

Here is a list of the species that occur in Central to North Central Texas starting at around Austin west and San Antonio north. Unless otherwise stated, assume that all species listed have 3 styles divided once (for a total of 6 branches) and that the leaves are entire. Plants are listed from what appears to be most to least commonly observed in the area on iNaturalist.

C. monanthogynus: 2 styles each divided once (4 segments); abaxial sides of leaves appearing brown-dotted; low annuals often branching at the base and without a strong main stem.
C. lindheimeri: Sepals longer than fruit, the tips curving inward to enclose the fruit at maturity; leaves often cordate at the base, rarely serrated; wooly annuals typically with a single main stem, not typically branching at the base.
C. glandulosus: Leaves serrated, low annuals often branching at the base and without a strong main stem.
C. lindheimerianus: Sepals distinct to base and widest at the apices; abaxial sides of leaves not appearing brown-dotted; low annuals often branching at the base and without a strong main stem.
C. texensis: Leaves narrow; tall annuals usually with long internodes, not typically branching at the base; sepals less than half the length of fruits at maturity; fruits with distinctive tufts of hair giving a warty or spotted appearance; styles divided many times.
C. fruticulosus: Leaves typically ovate, cordate and distinctly green adaxially; tall shrubby plants.
C. capitatus (east and north margins): Sepals longer than fruit, the tips curving outward at maturity; leaves not cordate; wooly annuals typically with a single main stem, not typically branching at the base.
C. alabamensis (rare): Large shrubs.
C. dioicus (west margin): Silvery perennial herbs, sometimes appearing subshrubby; leaves not acute; styles branches more than 6.
C. pottsii (west margin): Silvery-white perennial herbs, never subshrubby; leaves acute
C. heptalon (southeast margin): Like C. lindheimeri but with larger basal leaves, white hairs, and shorter ellipsoid seeds (4 mm long instead of 4.5 mm).
C. michauxii? (east margin): Leaves narrow and silvery abaxially; plants covered in yellow-orange glands.

For differences between C. capitatus and C. lindheimeri, see discussion and illustration in the Flora of North America treatment on Croton. Croton lindheimeri was treated has C. capitatus var. lindheimeri by Manual of the Vascular Plants of Texas and many other references. Flora of North America now treats this entity as a distinct species. Croton lindheimeri is by far the more common than C. capitatus in this region. By far the most distinctive characteristic is the differences in the sepals. The presence or absence of yellow hair as mentioned in FNA doesn't seem to hold up when looking at the observations here. The leaf characteristics seem to work well as long as you understand that C. lindheimeri is variable and often overlap in leaf shape with C. capitatus. If you see a plant with cordate leaf bases, it is almost certainly C. lindheimeri. The petiole characteristic is hard to use in most photos as those of plants much shorter than a person are typically taken from above making it difficult or impossible to see lower leaves. There is also a difference in the seeds described in Manual of the Vascular Plants of Texas but none of the photos on iNaturalist have seeds yet. Croton heptalon looks somewhat in-between C. capitatus and C. lindheimeri with the calices and leaf shape of C. lindheimeri (incurved sepal tips and cordate leaves), but the hair like that of C. capitatus (not yellowish). More distinctions can be found above. Discussion on the differences between C. heptalon and C. lindheimeri can also be found here.

List of some observations representative of C. capitatus:
https://www.inaturalist.org/observations/7768497
https://www.inaturalist.org/observations/7571553
https://www.inaturalist.org/observations/3929292
https://www.inaturalist.org/observations/1925854
https://www.inaturalist.org/observations/1822541
List of some observations representative of C. heptalon:
https://www.inaturalist.org/observations/14728137
https://www.inaturalist.org/observations/8535379
https://www.inaturalist.org/observations/14850391

P.S., Yes, there are three taxa named after Lindheimer: Croton lindheimeri, C. lindheimerianus, and C. glandulosa var. lindheimeri. Thank you Croton taxonomists.

Posted by nathantaylor nathantaylor, November 02, 2017 22:54

Comments

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I hope someone finds another species and names it Croton pseudolindheimeri. :)

Again, excellent curation on these Croton spp., Nathan! You're making iNat better and better.

Posted by sambiology over 1 year ago (Flag)
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Oh man. That would cause no end of confusion. At least you could call it the False Lindheimer's Croton. As it is, the common name Lindheimer's Croton really isn't all that useful. Thanks for the encouragement. I think I got all the C. capitatus/lindheimeri observations done, except for the ones that were too small or dead to ID.

Posted by nathantaylor over 1 year ago (Flag)
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Don't forget C. pseudolindheimerianus! Although I am starting to appreciate the *anus* part of that word.

Thank you Nathan for the ID corrections and the write up! I'm bookmarking this post!

Posted by kimberlietx over 1 year ago (Flag)
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Nathan, have you looked for C. heptalon, which was differentiated in FNA?

Posted by eric_keith over 1 year ago (Flag)
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@eric_keith darn. I missed that one because I had it listed as South Texas. Thanks for pointing it out! Time to learn another Croton...

Posted by nathantaylor over 1 year ago (Flag)
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So that was the odd C. lindheimeri morphotype that I was seeing in SE TX. Well, back to the drawing board to correct my mistakes.

Posted by nathantaylor over 1 year ago (Flag)
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@eric_keith Let me know if you find any information on how to separate C. lindheimeri from C. heptalon in a consistent way that can be seen in a picture. I'm having a lot of trouble figuring out where C. heptalon ends and where C. lindheimeri begins. Also, if anyone can provide pictures that include good style branches of young flowers in the areas where C. heptalon is supposed to occur, that would be great!

Posted by nathantaylor over 1 year ago (Flag)
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I just noticed that C. heptalon was differentiated. It's on my radar to look for differences.

Posted by eric_keith over 1 year ago (Flag)
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Shinner's and Mahler's says that the styles of C. capitatus (and maybe lindheimeri) can be more than twice-divided.

Posted by alisonnorthup over 1 year ago (Flag)
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@alisonnorthup good to know. I think most of the C. lindheimeri observations here have styles only twice divided.

I'm starting to think the style characteristic may require a much closer look than the observations here provide if they are even consistent (it is an easy trap for a taxonomist to fall into to make a bigger deal about a minute tendency than one should). The more elongated styles characteristic seems like it could be one of those tendencies. The branching, however, seems like it should be significant, though I am having considerable difficulty in interpreting it. The style diagrams in figure 1 of the original publication seem indistinguishable. The hairs seem more useful, but are inconsistent and can be found in many plants that otherwise look like and occur where C. lindheimeri, such as this observation. The seed characteristic may be the best to use when possible but that will have to be evaluated when I can get a chance to look at seeds of both species.

Posted by nathantaylor over 1 year ago (Flag)
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Thanks for this!

Posted by cwhiting over 1 year ago (Flag)

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