Plumerias can survive a short freeze even a dip into the 20s, but longer than 30 minutes will begin to kill the bud ends. When the temperature drops below freezing, the latex sap freezes.
If there is going to be a freeze spray water on your plumerias, This is exactly what citrus growers do during frost. The dry surface and dust will attract frost crystals to the plant and cause it to freeze, also the water on the surface will freeze and absorb all of the cold as it freezes, saving the plant underneath. If you can set the sprinkler to water them at 4 AM and 5 AM, which are the coldest points of the night, that would be excellent.
Wrapping up plumeria with a blanket or tarp or overhead plastic can also save the plant. But plastic to cover your plants because it will retain the cold under and help freeze the plant. Some people put cotton socks over the tips.
Incandescent (Old-fashioned non-LED) Christmas lights can be wrapped around the plant for additional heat.
Plumeria in Containers
Exposed plumeria in containers will be killed if left out in the frost.
- Before the Frost move the containers under a patio or protected roof area if not inside.
- Water them and spray them down
- Wrap them in a blanket
- Move them to someplace where they can get warm air or against a warm wall or building