They do die pack all the way, and send up new shoots in the spring from under ground The old growth is totally dead it will not leaf out come spring and can be removed, I usually leave it until the new growth shows above ground so I will know where it is at.
They love it wet. My white one is sitting in one of the pools with water from the drip standing in it.
This picture is early in the season, right after I set up the pool
My Fire Ball Hibiscus did not send up shoots last summer until July, this year it was May.
