Hardiness is not a simple issue defined by low temperatures. There are factors and factors involved; soil type, soil moisture, slope, the sequences of warm and cold and wet and dry.... and on and on. Some years plants on the "edge" sail through only to succumb to what might appear to be similar conditions the next year. It's not unusual for many borderline plants to last a few years or 10 or more, but eventually be killed by some peculiar combination of meteorological phenomena. Bearing all that in mind I have to think that this Vernicia is good in our zone. Last winter wasn't extremely cold but it was a legitimate Zone 7 winter which is uncommon enough here of late. We had a couple of days under 10 F, we had 40+ inches of snow, and something more than the top two inches of soil were frozen for weeks. This plant looked as good coming out of winter, actually better, than it did going in and it hasn't missed a beat. We've already got 6 leaves on a plant that, as I recall, had only 18 total last year.(Yes, I did count. Not every plant, but this one)
Rosa clinophylla, on the other hand may well be taking advantage of a winter without any extreme temperature swings; I wouldn't be surprised not to see it next spring, but who knows? It could outlast me. Nobody rates this above a 9a. It's a swamp rose ?!?! from tropical Asia: India, Bangladesh, Myanmar, Laos, and Thailand. And it looked miserable all summer. It's supposed to like heat and humidity. Go figure.
This last one is the real shocker. It's Brazilian Plume, Jacobinia sp., a 9b plant for sure. I somehow got confused about what it was and put it in the ground thinking it was a Shrimp Plant, Justicia Brandegeeana, which is more likely candidate for survival in Zone 7, being itself, only a Zone 8. I planted it in the courtyard of the Beltsville Library where it is a little protected and hoped for the best. Well, the leaves kept getting bigger and bigger and I realized it wasn't a Shrimp Plant and then it flowered, that distinctive pink mop of florets and I figured, whatdayouknow? I fed it and watered it thoughout the summer and figured people would be impressed with the flowers because, well, they're impressive. And it was well received but I had no hopes whatsoever of seeing it this spring, but there it is. It looks vigorous, as though it's ready to put up multiple shoots and become a very showy plant. I'm psyched.