What are the hardiest palms?

The following varieties can resist freezes down to -15°C (5°F) and some even lower, in order of decreasing hardiness: Rhapidophyllum hystrix, Sabal minor, Trachycarpus nanus, Sabal x texensis, Nannorrhops ritchiana, Trachycarpus takil, T. fortunei, T. wagnerianus, Serenoa repens, Jubaea chilensis, Chamaerops humilis var. cerifera and Trithrinax campestris.