Trachycarpus wagnerianus survival
I've been unimpressed with the hardiness of my one windmill palm (Trachycarpus fortunei)--damaged foliage and spear pulled 3 winters in a row (even after the unusually mild 2005-2006 winter); the first two times it recovered quite well come spring but after 7 degrees this past winter and extensive damage, there's still no sign of new growth and I'm not sure it's going to make it. Even if it survives, I may remove it because it just looks so awful every spring. I know other people have grown this species successfully in my area, but they generally have much more favorably locations.
On the other hand, my "waggies" (dwarf windmill palm, T. wagnerianus) have been doing fabulously well. I planted seeds in early 2001; the 3 largest are now about 6 years old, and have been in the ground through 5 winters. I protected all of them during their first winter, then protected only one of them (just as insurance) in the second and third winters; since then the only protection I've given them has been a heavy leaf mulch. They have grown fairly slowly but none of these three has ever had a spear pull; they came through 7 degrees this past winter with virtually no damage and are pushing out vigorous new growth.
The biggest surprise came from the runt of the litter. This seedling grew more slowly than the rest and was still very small when I finally planted it out last spring, pretty much just to give up on it. I put it in a poor location where it got watered infrequently and shaded out by other plants, then didn't protect it except for mulch (which I forgot to apply until after the weather had turned cold!). Because this was a cold winter I wasn't surprised that it suffered quite a bit of damage. By this spring the spear had pulled and only one relatively green leaf was left; the rest were fried. About a week ago I was about to pull it out when I saw, to my amazement, that it was pushing out a new spear! I guess I won't give up on this one quite yet! I'll try to get some photos posted later this week.
From my own experience, and from talking to other growers, I am absolutely convinced that this species is hardier than T. fortunei.