Will, I've mentioned this before in your threads, but it's hard revising my understanding of Washy hardiness. Prior to your wonderful and thorough documentation, I thought Washies were frond hardy to the upper teens and trunk/spear hardy to about 11F.

Where did I get those numbers? Through logical deduction based on others' experiences on this board and noting where Washies become commonly seen in public landscapes. They are seen along the coast in SC. And they very numerous from Savannah on south. They are a 9a tree, with a fair representation into good 8b locations. There is/was a "famous" one that was often presented here that grows/grew in Wilmington,NC. Seems to me if 17F is the fatal loss threshold, the species would have a hard time maintaining their footholds in the Wilmington to Savannah corridor. Every decade or so, temperatures in that area tend to dip into that 10F to 15F range. And no one if protecting those trees.

Your documentation is, to me, definitive. You have much more hands-on experience with Washies than I do. Thanks for sharing your results, and the pictures are terrific.