Missy Gable is the program manager at the California Center for Urban Horticulture at UC Davis. She says frost-tender plants don't adjust well to the onset of cold temperatures. 

"Plants have a hard cell wall and when we have freezing temperatures the water inside those cell walls freezes and it expands and that can damage the cell wall or even cause it to rupture."

Gable says if you're covering your plants, don't use plastic. She says woven material such as old sheets provides little pockets of air that help keep the plants a little bit warmer.

Frost-tender plants include: cactus, succulents, citrus plants and begonias.