Thanks Adam, it would be very nice if they can get 25º F (-4º C) and survive in a protected place where colds can get 20º F (-6.6º C), under other bushes and with automatic watering. We planted one of them in that place now and hope that will be fine this winter... maybe will put an anti frost blanket
If wind is not intense, you can protect by letting them ice over during a freeze, I did this just recently for 26F and 25F, two separate hard freezes, about 10hrs total duration at those minimum temps, the irrigation must be started before the onset of freezing weather, (38-36F works for me, I start early because I've had the water start to freeze inside my pipes before it actually froze), and you mustn't stop watering until the freeze has passed, I wait for temps to rise above 36F, and then I stop irrigating
The process of ice forming actually generates heat
http://littleshop.physics.colostate.edu/tenthings/FreezingWarmer.pdfOne bad thing is that if you water too much and the freeze is too hard, it can produce so much ice, it weighs down the branches and breaks them...good thing jaboticaba wood is very strong, mine held what seemed like 60lbs of ice armor.