A trait useful for identification in the Sabal genus?

[Phoenikakias]

This Sabal has prominently inwards recurved margins of hastula and costa. Is it a random occurence or a constant feature of a particular Sabal sp?

[Phoenikakias]

And costa

[Phoenikakias]

For comparison next two pictures show margins of hastula and costa on my Sabal causiarum (identification based on ligules). Some people consider doubtful the use of ligules as distinctive feature of causiarum. Nevertheless fact is fact that discussed here feature of recurved margins is absent on a different Sabal sp. Note how open are here the margins.

[Phoenikakias]

And costa

 

[sonoranfans]

Differentiation between causiarum from domingensis alone requires (3)orders of branching vs (4) and 7-10mm fruits vs 11-14mm(?) fruits according to Zona in his 1990 sabal monograph.  If a hastula form was confirmatory, I'd think he would have seen that as its an obvious morphological trait.  Ligules may or may not be definitive, not sure that observation came from habitat.  I think the work of Zona still stands as the most comprehensive study of Caribbean sabals.

[RJ]

I purchased this sanbal  as an unknown , however am leaning towards causiarum. 

Edited June 21, 2019 by RJ

[PalmatierMeg]

Sabal causiarum has papery ligules vs. domingensis, which doesn't

[sonoranfans]

In the case of my causiarum(defined by 3 orders of branching of inflorescence and fruit ~8mm as above), there were no ligules till just before trunking.  About 5 years in the ground from a 7 gallon strap leaf seedling and over 12' tall, I started seeing small ligules 4".  today they are there no doubt.    Because I believed the "ligules" argument was definitive, I though my palm was, as labelled, S domingensis.  Today, 8 years after planting it has a massive fat trunk and ligules and has been setting seed for the last 2 years..

[Steve in Florida]

None of my Sabal causiarum have ligules.   I looked through photos of a half dozen wild trunked specimens in Puerto Rico and they did not have ligules either.  If I grow them from seed they are easy to distinguish from S. domingensis.  The latter develops tall bifurcated leaves which linger for multiple seasons.  They also can't take frost.  S causiarum goes from strap leaves to mutisegmented fan leaves like S. palmetto, only larger.  They are also much more cold tolerant as I've seen mine take 19F and .50" of freezing rain without a blemish. while my S. domingensis would die to the ground at 25F. 

[Fusca]

27 minutes ago, Steve in Florida said:

If I grow them from seed they are easy to distinguish from S. domingensis. 

Seed size difference between causiarum and domingensis seems pretty obvious to me.  I recently received some different Sabal seeds I've not tried to grow before and decided to measure them to compare with what I have read.  As Tom mentioned above, what was labeled as causiarum measured 7-8mm wide and 5mm tall, domingensis 10-11mm wide and 7-8mm tall, and maritima 8mm wide and 5-6mm tall.  

[sonoranfans]

On 6/21/2019 at 1:01 PM, Steve in Florida said:

None of my Sabal causiarum have ligules.   I looked through photos of a half dozen wild trunked specimens in Puerto Rico and they did not have ligules either.  If I grow them from seed they are easy to distinguish from S. domingensis.  The latter develops tall bifurcated leaves which linger for multiple seasons.  They also can't take frost.  S causiarum goes from strap leaves to mutisegmented fan leaves like S. palmetto, only larger.  They are also much more cold tolerant as I've seen mine take 19F and .50" of freezing rain without a blemish. while my S. domingensis would die to the ground at 25F. 

Hi steve, interesting observations since you have had both.  I had small, 6-8" ligules on a sabal blackburniana in arizona, so I have been thinking its an adaptation outside natural environment or something like that.  My current causiarum is a beast, bigger than my bizzies in width of trunk and crown, and it has good sized ligules.  It was years(~5) before they developed.  I bought it as a "s. domingensis" from tejas tropicals(no longer around) as a 4"x12" pot seedling in 2011.   the branching of 3 orders  on the infloreescence and the ~8mm fruits confirmed as directed by Scott Zona (in his sabal monograph) confirmed it for me.