What are some hearty palm trees?
The hardiest arborescent (trunking) palm is the Windmill Palm - Trachycarpus fortunei. These are grown as far north as parts of British Columbia in Canada. They have a fuzzy trunk which can grow twenty feet tall. They do not need a hot climate, and seem to thrive in cool, moist weather.
Sabal palmetto (Sabal palm, Cabbage palm) is the state tree of Florida and South Carolina.
It has been known to survive between zero and +5° F when well-established. It cannot survive these temperatures on a regular basis, and is probably best rated as zone 8a. It is a large Fan Palm which takes many years to form a trunk.It can be found in the wild as far north as Bald Head Island, North Carolina, near Wilmington.