[Arid_gardener] Bouganvillas - Winter Problems

[Kelly Conroy]

I have two bouganvillas in my back yard for 3 winters now.  I have
another that is in its second winter.  Everytime we get a freeze, the 3
winter bouganvillas shrivel, dry up and "die".  However, if I cut them
down to the trunk in the spring, they regrow.  I was under the
impression that these only go dormant (if that's the right word) for the
winter during their first season and that they should stay green
throughout winters after that first winter season.  Yet mine shrivel up
each winter and need to regrow each spring.  Why is this?  I can't cover
them during freezes because they grow to be enormous and they are the
type that poke out in 10 different directions, making them difficult to
cover.  

Can anyone make any recommendations as to how to prevent them from
shriveling up every winter?   That other bouganvilla, in it's second
winter, has not shriveled up this year (it did last year, it's first
winter).

~ Kelly