Depending on the type of succulent, how low temperatures drop (water freezes at 32 degrees F), and how long the cold snap lasts, “frost tender” succulents may show damage just on leaf tips or collapse into mush.
When moisture in the cells of a vulnerable plant freezes, it expands and bursts cell walls. A few succulents have a built-in antifreeze, and survive temperatures well below 32 degrees F—below zero, in fact. But these are the exception, and tend to be in the genera Sedum and Sempervivum.
Crassulas, aeoniums, euphorbias, and kalanchoes are among the most tender succulents. The majority of aloes, echeverias, cacti and agaves can go a few degrees below freezing for a short period.
Check the forecast, and if there’s a frost advisory for your area, cover susceptible plants with frost cloth (sometimes called garden cloth, frost blanket or floating row covers) or old bedsheets.
When determining if a tender succulent needs to be covered, I sometimes stand over it and look up. Plants beneath eaves or tree branches are not as vulnerable as those open to the sky.
Cold air is heavier than warm, and flows down slopes and collects in low spots. Consequently, succulents in swales are more at risk than those atop berms.
You may have heard that Christmas lights raise the temperature a few degrees. Yes, if they’re the old-fashioned kind. Those sold nowadays (LEDs) don’t generate heat.
Wait until spring to trim damaged tissue. It’ll help protect the plants from further damage.
Watch how I cover my own tender succulents in my new video, “Protect Your Succulents from Frost.”