The are several major difficulties with what might seem the obvious FNA–based identification.
Although the FNA treatment of Sabal gives a reference to the Brazoria palmettos as possible hybrids (somewhat inconsistently in its treatments of S. minor and of S. mexicana), a possible relationship of the Brazoria palmettos with S. palmetto has only recently has been supported (cf. Goldman, Phytotaxa 27 ). [Although I do not have a S. palmetto fruit image, these as well as those of S. minor are the same size as the smaller fruits above. The fruit mesocarp of both Praha and Brazoria palms is fleshy, not thin and papery as with S. minor.]
Inflorescences ... equaling or exceeding leaves in length.The inflorescence of the Praha palms is contained within the leaves, as is that of the Brazoria palmettos. But Zona (personal communication, 2007) questions whether "inflorescence length is a stable, useful character."
Inflorescence of Praha palm.
Inflorescence of S. palmetto.
This [the Praha palmetto population] is the only case I know of S. palmetto escaping into the wild in Texas. Normally it doesn't escape into the wild. Although I've never investigated the matter I have heard that S. palmetto is commonly dug up in Florida and shipped to Texas.One must consider the possibility that the Praha palms, unlike those imported from Florida and maintained in gardens, are already adapted to Texas conditions, ultimately from a native source in the 19th century. Again, the Brazoria palmetto has shown the ability to survive and escape into the wild well north of the coast, in the Texas hill country.
A somewhat different view has been expressed by Zona (personal communication, 2007):
I would guess that Sabal palmetto will escape wherever it is cultivated, as it has in Louisiana, western FL and probably elsewhere. The seeds get around. One wonders why its range hasn't naturally expanded to include Louisiana and southern Texas. [Emphasis by Harms]
The Louisiana populations of S. palmetto noted by Zona are probably at Lake Charles, Calcasieu Parish on the Texas border, described in Principes 40 (1996) by Landry & Reese. Several groups of palms were found essentially adjacent to (old) US 90 (i.e., these days as Interstate I-10), which runs from San Antonio to a few miles north of Praha to Lake Charles (and east). It also parallels the railway (Southern Pacific) which linked San Antonio with New Orleans in the later 19th Century.
Landry & Reese suggest that these palms are from cultivated palms introduced in the 1960s along a man-made beach, but they found no volunteers at that site. They report "more than 200 plants (numerous seedlings, young plants, and several mature trees) ... just east of the Calcasieu River near the base of the ... (I-10) bridge over the Calcasieu River." Yet another site had some tall palms but no seedlings or very young plants. Harms note: The variation in the extent of adaptation of the palms at the various Lake Charles sites is not accounted for by Landry & Reese. The possibility of more than one source – even Brazoria palms – must be considered.
Mulberry Creek enters the West Navidad River some 10 miles from Praha, leading to the Lavaca—Navidad basin, with the Lavaca River entering Matagorda Bay on the gulf coast. The area above the bay is one for which reports of arborescent palms have been noted since the 17th century. For example, in Henri Joutel's 1685 journal from the La Salle Expedition (Warren translation, p. 124) he notes:
tree which has long branches of about three or four feet and its leaves are like those of palm trees[fn 23] but are taller and wider. They bear a small fruit, but I do not know how to describe the taste, not having eaten any. One of our men told me that it seemed good to him.Footnote 23: Cheatham and Marshall report that this description reads more like Sabal texana (aka S. mexicana in some works) and that Garcitas Creek is one of the known sites for S. texana.
Harms note: Everyone agrees that S. mexicana at the Garcitas Creek site are of recent origin, whatever their ultimate source.
Later, in Ferdinand Lindheimer's letters to George Engelmann in 1845 [Goyne's translation as corrected by Lockett (Sida 16:712, 1995)]:
I collected seeds of the fan palm with stem that is often 20' to 40' high.Lindheimer, rightly or wrongly, identified the palms he observed just inland from Matagorda Bay as S. palmetto (using its scientific synonym Chamaerops palmetto).
Texas Parks and Wildlife natural resources director David Riskind observed arborescent palms in the Lavaca/Navidad bottomlands in the mid 1960s before they were flooded. But, as he recalls (personal communication):
I never looked at them carefully, nor were any photographs or specimens taken. At the time I was doing archeological reconnaissance and I have no way of knowing where the plants were observed.A critical review of the current literature on Texas palms reveals that there is no direct evidence, either historical or biological, that would permit identification of the native (not introduced/escaped) tall palmettos outside the Lower Rio Grande Valley as S. mexicana. One cannot with certainty rule out the possibility that the early palms of the Central Coast were Brazoria palmettos or perhaps even related to the Praha palmettos.
The possibility of a more extensive distribution of the Brazoria palms is presented by Jill Nokes (2001, p. 452):
Some botanists believe that Brazoria Palmetto probably once occurred extensively on Galveston Island, as larger palms were once recorded there. There may have been more extensive palm lowlands along the Gulf Coast uniting those species 12,000 years ago, before the Gulf of Mexico gradually inundated the present day coastline (Ogden, personal communication, 1999).Nokes doesn't identify the botanists, but of interest is the absence of the commonly invoked 'tall palm syllogism' (i.e., Texas has only one tall palm species, S. mexicana, therefore reports of a tall palm demonstrate the historical presence S. mexicana).
One recent DNA study of the Brazoria palms supported by Lockett added yet new possibilities — with implications for the historical tall palms north of the Lower Valley (personal communication from Lockett, June 2007; emphasis mine):
Mark Brunell, a University of the Pacific botanist, has done genetic research on the Brazoria palms and now believes this palm is either a new species or a hybrid of S. minor and some now-extinct Sabal. This palm is known only from a small area of Brazoria County, although there could be more in the thick woods surrounding the site. It is prolific and has been planted widely.
Although Brunell's study did not include either the Praha palms or S. palmetto, the latter was included in Goldman's recent (2011) work establishing the hybrid status of Sabal × brazoriensis and suggests a possible close relationship with S. palmetto.
As for more recent palm sightings that are yet to be investigated, one must entertain the possibility that the Praha plants are old enough to have produced seeds that traveled down Praha's Mulberry Creek to the lower Navidad. It may be necessary to wait until the young palmettos seen in the area mature and produce fruit that a firm ID can be made.
The currently recognized native range of S. palmetto is restricted to the southeastern United States, not extending west of the Florida panhandle.
One possibility that can't be rejected off hand is that the distribution of S. palmetto once stretched from Florida to the Central Texas Coast, and inland. And that early historical sightings as well as later palmetto populatons at Brazoria and Praha, perhaps also some in Louisiana, are evidence of an earlier S. palmetto population.