Ummmmm...as a Floridian, who's Growing Palm Trees.....you are correct, except for coconut palms ....they absolutely love saltwater, even better used saltwater from your tank with all the nutrients in it. I always dump my used 5 gallons at a time directly on to my coconut palm and it loves it!
My coconut palm has grown twice as fast as the person I got mine from , who was the Original grower, his and mine are not even close any more.
Some plants at least in Florida actually love and need Saltwater!