Prior to citrus being grown commercially in Florida the plantation owners of the sea island where I live brought citrus back from Spain and started growing it here. The plan was that it was supposed to be a cash crop but the "late unpleasantness" in the late 1800's put the kibosh on that idea. I would imagine the occasional cold weather would have done the commercial aspect in eventually.
Our water table is close to the soil surface, about 2' down you hit water on a good day and it is salt water. Amazingly, grapefruits thrive around here, the trees are enormous, I have seen some 40' high with fruit rotting on the trees because no one can get up there to pick it without a bucket truck. They must love the extra moisture. My own grapefruit tree looks good, the leaves have good color and no blotching or dimples, but the fruits all have a brown spot on the skin. It looks like a place where the fruit might have rubbed a branch or something but every fruit has a blotch or two. It is all on the surface, the flesh itself is fine and still tastes right. There is a slight stain beneath the calyx, not sure if that is truly indicative of greening in my case or not.
It is raining again today and the tides are unusually high so the rain has no where to go. This has been an unusually wet year, come spring we will know what has survived and what has drowned. We actually had a weather warning the other night about trees falling from the saturated ground.
See that pink stain on the calyx?