Frost damage occurs in a plant when the liquid inside the plant's cells turns to ice. This damages the cells and prevents the plant from obtaining water. Frost-damaged plant tissue looks water logged and wilted when the damage first occurs. Eventually the foliage will turn dark brown or black. If the damage has affected enough of the plant's tissue, it is unlikely to recover. But there is no way to know the extent of the damage until your plant begins producing new growth in the spring. Therefore, the University of California's Horticultural Advisor suggests that gardeners wait until then to assess frost damage and try to revive the plant.
Move your houseplant indoors immediately. After a houseplant is frost damaged and defoliated, it suffers a higher risk of sunburn.
Remove all of the frost-damaged fruits from containerized fruit-bearing plants and trees. This fruit will rot quickly now that its cells are ruptured. Furthermore, supporting this damaged fruit puts the tree under more stress.
Prune away the parts of the plant that are visibly damaged and fail to produce new growth by summer.
Dilute the plant's fertilizer application by 1/2 until it has fully recovered. Now that some of its foliage is gone, it has more roots than it needs and may produce rapid new growth. Withholding fertilizer will stabilize some of this growth.
Cut severely damaged perennials and shrubs back to the soil line if they show no signs of life at the beginning of the growing season. Your plant may indeed be dead, but cutting it back may stimulate it to produce new growth. However, if your plant produces no growth during the season, it is likely dead.