We haven't had many hard freezes in the past few years but delicate sub-tropicals i.e. bougainvillea, gardenia, mandevillea, hibiscus etc.................need some help even in mild winters.
Spray these plants in early December with Wilt-pruf or Cloud Cover anti-dessicants to help them survive the winter cold.
If there is a warning out for a hard freeze cover plants with an old sheet or ground cloth (never plastic!)
supporting cloth off of the foliage. Putting a lamp or light (turned on) below the cloth adds heat to help in a freeze.
Move potted sub-tropicals under an overhang on a warm wall (south or west facing).
When planting these plants try to locate them below an eave on a warm wall so that even in winter the wall will warm in the day and retain some heat at night.
Avoid pruning back frost damaged areas of plants until way after the last freeze to allow plants additional coverage from old foliage and to see where new sprouts will appear.