This isn't completely correct.. While not " Humid " when compared to S.E.'rn US standards, typical, annual humidity levels in much of CA are more than adequate for most ...if not all... the Sabal sps.. Heat is good enough as well, except maybe in a few spots like San Francisco < though i'm sure the commonest sps would do < are doing?? > fine there > and always chilly areas along the north coast, north of San Fran.
Even here in the ...much drier.. / Quite a bit hotter low desert section of AZ there are folks growing perfect looking " Eastern " Sabals
..If they will grow well here, no doubt, they'll do fine in CA. ...more parts of the state than not at least.
BIG part of the reason Washingtonia could be considered the most common fan palm in this part of the world, compared to Sabal sps. comes down to which was introduced here, first..
..To that end, everyone can thank the Spanish explorers for bringing W. robusta w/ them from Mexico ..On a much more visible - to -all scale than probably had been seen at the time, even if the species / form of Washingtonia itself were already present in specific spots in say AZ or areas of CA closest to the Gulf of CA / Sea of Cortez..
Canary Island Palms, and Schinus molle, aka " CA " Pepper Tree were additional " Spanish Settler imports " brought into CA ( and AZ ) when they settled missions and larger homesteads / Ranchos.
They probably liked W. filifera so much when they saw it that it too became a popular thing to plant on their ranches / within Mission gardens..
After that? newer settlers in CA " caught the bug " ..so to say, and sealed the " iconic status " fate of both Washingtonia and Phoenix canariensis.. Pretty sure you can toss in Jubea as well, though i think it was a later import that didn't garner quite the same level of popularity compared to Canaries at that time.. Could be wrong ofcourse..
No one ( that we know of ) brought Sabal -anything- species with them when they headed west from the eastern US, so... It is only now that people in the west are being introduced to that Genus of Palms.
In time, if promoted, they'll probably take their place in " Palm Star Status " in CA landscapes..
....Reverse is a big reason why Sabal ..palmetto in particular.. is the eastern / southeastern US equivalent " Washingtonia " ..It is what was around, well known, and easy to access..
..Folks there didn't know what a " Washingtonia " was until much later in time..
As far as Sabal uresana, carefully study the climate where it grows in Mexico, both forms of it.. ...somewhat Southeastern US -ish, minus the constant Arctic Invasion threats during the winters, esp. along the coastal plain.. Not quite the same as what people associate with California ..For the moment at least.
It is however the Saba sp.l i myself would widely promote out there, before all others except species within " Caribbean " group.
" Slow " is a word used only by the " i want instant gratification clan " To the rest of us, Sabal do, what they do after planting..
Treated well, they'll get to where we hope they do, when they do..
See the above..