Brazoria Palmetto Origin Theories

[L.A.M.]

I wonder, what is the true origin of the Brazoria palmetto (Sabal brazoriensis)? The possibility of hybridization with Mexican palmetto (Sabal mexicana) has been disproven with genetic analysis, even though geographically a hybrid of that and dwarf palmetto (Sabal minor) may seem logical due to them being the only other palm species native to Texas. Some other possibilities for the origin of the Brazoria palmetto already mentioned in scientific literature:

1. Hybrid of cabbage palmetto (Sabal palmetto) and dwarf palmetto
2. Hybrid of dwarf palmetto and an unknown, now-extinct palmetto (Sabal) species
3. Completely new palmetto species of unknown origin
4. Hybrid of cabbage palmetto and an unknown, now-extinct palmetto species

Personally, I'm inclined to think scenario 3 is the likeliest. Greenland ice core data for the climates of the last 120,000 years shows that the area where the Brazoria palmetto is native to had marginally mild winters at the height of the Last Glacial Maximum, and they're known to be reliably cold-hardy well into the single-digits degrees Fahrenheit in places like Murfreesboro when planted elsewhere (unlike cabbage palmettos and Mexican palmettos which would perish in most of Tennessee). One Murfreesboro palm grower even says they're more cold-hardy than the Birmingham palmetto (Sabal 'Birmingham', widely believed to be a modern hybrid of cabbage and dwarf palmettos) and the smaller trunking Louisiana palmetto (Sabal minor subsp. louisiana). This seems to suggest speciation and that Brazoria palmetto is a glacial relic hardened to survive a climate similar to modern Tennessee to avoid extinction in glacial periods. This video shows reconstructed climate data from North America: 

The video doesn't show the effect of the Labrador Current on the immediate East Coast's climate during Heinrich events, but the author acknowledged in a comment that showing short-lived microclimates would test the limits of their model. This also is irrelevant along the Gulf Coast and inland, which the marine layer over the periodically supercharged Labrador Current (responsible for localized permafrost forming Carolina bays) did not reach. I see no reason to doubt the accuracy of the data even in Appalachia, let alone central North America.

I also recently stumbled upon this article about a mysterious Braha palm species that is native further up the Brazos River valley in Texas and physiologically very similar to Brazoria palmetto. https://w3.biosci.utexas.edu/prc/Sabal/PrahaPalmID.html Could this be a disjunct population of Brazoria palmettos introduced by migratory birds, vagrant herbivores or even deliberately by Native Americans or Euro-American colonists (perhaps unaware of what it truly was)? Really, the only way to find out for sure may be to try to plant seeds from the mysterious Braha palm in a part of Oklahoma, the Ozarks, Tennessee or Western North Carolina that's firmly too cold for cabbage palmettos to survive long-term and precarious for Louisiana and Birmingham palmettos (which the part of Tennessee I live in is) but plant the seedlings in April of whatever year they're sown to maximize the chances of them fully establishing in their first growing season. I digress, though. If they are in fact Brazoria palmettos, this further suggests that Brazoria palmettos are likely a glacial relic with a very inelastic natural range and rely on their extra cold-hardiness to survive glacial periods when inland parts of the Texas Triangle have continental climates; intermittent desertification from the west and variable sea level from the southeast would also force Brazoria palmettos to spread (which they have largely failed to do) or adapt to their tiny range in Brazoria County and parts of neighboring counties (which they do seem to have done based on climate reconstructions of North America's past and successful Brazoria palmetto plantings right here in Middle Tennessee).

[Zeeth]

I suspect that the Praha palms that you allude to are something unique, but I don't know exactly what. They did get cold damage during one of the bad freezes a few years ago which I wouldn't expect with a S. brazoriensis. Pictures of that can be seen on this post:

If they are a hybrid, I would think maybe S. palmetto x mexicana based on the appearance of the leaves.

[L.A.M.]

6 hours ago, Zeeth said:

I suspect that the Praha palms that you allude to are something unique, but I don't know exactly what. They did get cold damage during one of the bad freezes a few years ago which I wouldn't expect with a S. brazoriensis. Pictures of that can be seen on this post:

If they are a hybrid, I would think maybe S. palmetto x mexicana based on the appearance of the leaves.

If what is a hybrid? Maybe the Braha palm could be, but scientists already used DNA evidence to rule out a close ancestral relation between S. brazoriensis and S. mexicana. Maybe Braha palms could be a hybrid of those two instead of of S. palmetto, though?

Also, how cold did that freeze get at St. Mary's Church? Context is important.

[amh]

I have 2 of the Praha sabals and they are the slowest sabal I have grown. The seeds are small, unlike S mexicana.

It is possible that these are S. brazoriensis from the western edge of its range.

https://w3.biosci.utexas.edu/prc/Sabal/Sabal-juven.html

[Chester B]

8 hours ago, amh said:

I have 2 of the Praha sabals and they are the slowest sabal I have grown. The seeds are small, unlike S mexicana.

It is possible that these are S. brazoriensis from the western edge of its range.

https://w3.biosci.utexas.edu/prc/Sabal/Sabal-juven.html

I'm not finding that, I would say average Sabal growth rate.  I have one in the ground and the other will likely be planted next year.  I have some Mexicana to compare them to but no palmettos other than small volunteers.

[amh]

3 hours ago, Chester B said:

I'm not finding that, I would say average Sabal growth rate.  I have one in the ground and the other will likely be planted next year.  I have some Mexicana to compare them to but no palmettos other than small volunteers.

It could be that mine suffered some transport shock. The plants are slow, but I do notice that they are maturing faster than Sabal minor.

I am inclined to believe that these are a form of Sabal brazoriensisor or independently occurring hybrid, but I am very open mended to alternatives.

[Chester B]

4 hours ago, amh said:

It could be that mine suffered some transport shock. The plants are slow, but I do notice that they are maturing faster than Sabal minor.

I am inclined to believe that these are a form of Sabal brazoriensisor or independently occurring hybrid, but I am very open mended to alternatives.

I think they’re palmettos.  Some of the palms are very tall, much more so than any brazoriensis I’ve seen.  As well brazoriensis have a haphazard boot pattern but these have a uniform pattern like most trunking Sabals. 

This is just my opinion. I always lean toward the most probable and unfun answer to things that are a mystery.  The railroad went through there and palmettos are likely the most common Sabal in the US. When I look at the photos of the Praha palms to me they look like regular palmettos. But I do plan on seeing them soon in person real soon. 

[awkonradi]

Some published research suggests a hybrid of S. minor and S. palmetto.

27144-Article Text-20581-22462-10-20190319.pdf

[L.A.M.]

On 11/13/2025 at 1:13 PM, amh said:

It could be that mine suffered some transport shock. The plants are slow, but I do notice that they are maturing faster than Sabal minor.

I am inclined to believe that these are a form of Sabal brazoriensisor or independently occurring hybrid, but I am very open mended to alternatives.

I read the article and looked closely at the articles. They look like either an outlier Sabal brazoriensis population or a Sabal brazoriensis x minor hybrid (perhaps descended from a vagrant S. brazoriensis population that got wiped out at some point, or a vagrant hybrid population itself with the originals still undiscovered in the S. brazoriensis range or having been outcompeted), although them supposedly being less cold-hardy than both is very odd.

[L.A.M.]

On 11/13/2025 at 6:55 PM, awkonradi said:

Some published research suggests a hybrid of S. minor and S. palmetto.

27144-Article Text-20581-22462-10-20190319.pdf 1.96 MB · 4 downloads

I read the article and looked at the diagrams. Thanks for sharing!

Personally, I'm still inclined to believe S. brazoriensis is a new species. Nonetheless, it seems to be a more recent descendant of S. minor than S. palmetto is, given that that diagram seems to suggest S. brazoriensis is more closely related to S. minor (unsurprising, given their comparable cold hardiness that S. palmetto lacks) but too distantly related to backcross. The smooth underground trunks in that other person's document are also telling; S. palmetto has rougher underground growth in that image, although S. minor also has a black coating that S. brazoriensis evolved out of like S. palmetto previously did, suggesting speciation if it isn't a S. palmetto x minor hybrid - which is still possible on million-year timescales, especially if those hybrids backcrossed with S. minor during the Pliocene or the less severe glaciations of the early Pleistocene prior to 1.2 to 0.6 mya but stopped backcrossing at some point.

Whether it evolved gradually or has a Pliocene or early Pleistocene hybrid origin, perhaps S. brazoriensis just represents a more advanced stage of speciation with taller trunks than S. minor subsp. louisiana and a trend back towards becoming more cold-hardy (S. minor subsp. louisiana is only reliably cold-hardy to 5 degrees Fahrenheit, not 0, according to @Allen in Murfreesboro). It would seem that southern Louisiana may be a favorable location for arborescent speciation on paper but that the shift to continental climates there in places above sea level during glacial maxima would wipe them out if they couldn't migrate to the continental shelf in time and back up when sea levels rose again. On the other hand, S. brazoriensis has a range that seems to have maintained at least a Kentucky-like climate, probably even Tennessee-like, during glacial maxima and is safe from sea level fluctuations and the intermittent expansion and retreat of deserts - allowing S. brazoriensis to keep evolving for hundreds of thousands of years (not just tens of thousands during interglacials) without having to migrate but also incentivizing it to be slightly more cold-hardy than S. minor subsp. louisiana and substantially more so than S. palmetto.

Keeping these things in mind, S. minor subsp. louisiana seems to be a speciation in progress but limited by climate and sea level fluctuations, whereas S. brazoriensis seems to be a complete but geologically recent speciation of S. minor that has had more stability than S. minor subsp. louisiana but also still having incentive to adapt to winters comparable to modern-day Middle Tennessee or Western Kentucky. Unfortunately, S. minor subsp. louisiana has clearly not yet had enough time to regain its diminished cold-hardiness through natural selection, and likely previous attempts at speciation in Louisiana have either been wiped out by a shift to continental climates or by failing to escape the subsequent sea level rise from the continental shelf - either of which has clear potential to claim any nascent plant species with a localized range there within 50 millennia if it can't adapt to a continental climate, which no palms can (they can adapt to days- or weeks-long hard freezes in marginally subtropical or oceanic climates, but the ground freezing like it does in continental climates will kill them).

[awkonradi]

Given the high mobility and durability of pollen, I think gene flow is steady, if slow, between many different "species" of palms.  I think this is true within Sabal, Phoenix, and Washingtonia, within which all "hybrids" are vigorous and fertile.

[amh]

On 11/13/2025 at 6:19 PM, Chester B said:

I think they’re palmettos.  Some of the palms are very tall, much more so than any brazoriensis I’ve seen.  As well brazoriensis have a haphazard boot pattern but these have a uniform pattern like most trunking Sabals. 

This is just my opinion. I always lean toward the most probable and unfun answer to things that are a mystery.  The railroad went through there and palmettos are likely the most common Sabal in the US. When I look at the photos of the Praha palms to me they look like regular palmettos. But I do plan on seeing them soon in person real soon. 

I initially was of the same mind, until I started growing Sabal palmetto. The Praha palms could very well, just be a very slow growing S. palmetto with thicker underground growth. I'm not married to any particular identity, but if these are S. palmetto, they are a very cold hardy form.

[amh]

On 11/17/2025 at 1:20 AM, L.A.M. said:

I read the article and looked closely at the articles. They look like either an outlier Sabal brazoriensis population or a Sabal brazoriensis x minor hybrid (perhaps descended from a vagrant S. brazoriensis population that got wiped out at some point, or a vagrant hybrid population itself with the originals still undiscovered in the S. brazoriensis range or having been outcompeted), although them supposedly being less cold-hardy than both is very odd.

In my opinion, there is just too much trunk for these to be back crossed with minor, perhaps it is a brazoriensis crossed with palmetto, or just a palmetto ecotype of unknown origin.

The historic ranges for Texas palms are probably less than accurate, I think the interest in palms is fairly recent, so people in the past did not pay much attention to what was growing.