Freezing is really bad for plumeria, but frost can do some severe damage also. One method we use is to turn the sprinklers on before sunrise and allow them to run until the frost has gone our cars. Frost damage occurs on plumeria leaves, branch tips and blooms when the sun hits the ice crystals.
The following list are some meteorological conditions that can lead to frost conditions, I hope it helps:
- Clear skies lead to radiational cooling, allowing the greatest amount of heat to exit into the atmosphere.
- Calm to light winds prevent stirring of the atmosphere, which allows a thin layer of super-cooled temperatures to develop at the surface. These super-cooled temperatures can be up to 10 degrees cooler than 4-5 feet above the surface, where observations are typically taken. For example, if conditions are favorable, air temperatures could be 36 F, but the air in contact with the surface could be 30 degrees or colder.
- Cool temperatures, with some moisture, that promote ice crystal development. If the super-cooled, freezing temperatures can cool to the dew point (the temperature at which, when cooled to at constant pressure, condensation occurs; moisture will have to come out of the atmosphere as fog, frost, etc) frost could develop on exposed surfaces.
- A local study done on frost formation relating temperature to dew point has these guidelines for frost: temperatures from 38 to 42 F can lead to patchy frost, 33 to 37 areas of frost, and 32 and below widespread frost/freeze. Note that the study did not factor in other considerations to frost, such as sky cover and wind speeds.
Local topography has a large role in determining if and where frost develops. Cold air will settle in the valleys since it is heavier than warm air, therefore frost conditions are more prone in these regions. Valleys also shelter the area from stronger winds, enhancing the potential for frost.
Other local effects, such as soil moisture/temperature and stage of vegetation “greenness” are factors that can affect the possibility of frost forming.
If plumerias suffer frost damage from freezing temperatures, prune the damaged areas to help the plant recover.
- Prune as soon as possible after you seed frost of freeze damage. The Pruned tips are more fragile and can be more susceptible to cold weather and may suffer even more damage if temperatures are below freezing after they are pruned. In addition. Frost or freeze damage with show up the next day on leaves and within a few days to a week.
- Determine the extent of the damage. Leaves may turn brown or black and hang from the stem usually when a day or two. Stem damage appears as soft, mushy tips that may ooze a brownish fluid. Squeeze stems between your thumb and forefinger. If you feel separation of tissue inside the stem, it is damaged and should be pruned. Loss of the entire plant is possible after hard freezes.
- Cut damaged leaves 1/2 to 1 inch from the plant stem with sharp pruning shears, leaving a leaf stub. Never pull off damaged leaves. The leaf stubs will dry out and later fall off on their own.
- Prune damaged branches with sharp tools. Cut small sections off at a 45-degree angle until you see only white, woody pith at the cut. Swab cutting blades between cuts with rubbing alcohol or hydrogen peroxide to prevent introduction of bacteria into fresh cuts.
- I is a good idea to seal branch cuts with lime paste or latex caulk. The lime paste has a natural antifungal element in it.
- Do not allow the plants to dry out completely, but too much water will damage them further.
- Always Protect pruned plumeria from exposure to temperatures lower than 40 degrees Fahrenheit. You should always protect plumeria from freezing temps of when there is a danger of frost.
Protect from frost or light freeze:
- Using plastic to cover your plants will retain the cold, if the tip touch the plastic it will damage the tips.
- Old Socks on the tips.
- Cover with frost cloth
- Use old style outdoor Christmas lights or outdoor light bulb under the covering. Make sure they are not LED.
- Freeze damage normally will not travel down the plant, but check to see how far the damage actually goes. Freeze damage will come up from the bottom of the plant.
- Sometimes you will need to cut all the way to the trunk. As long as you have live roots, the plumeria has a good chance of surviving.
When temperatures drop below freezing, the latex in Plumeria freezes. Once you decide to cut the plant you need to make sure you cut to good white wood with no signs of black or brown.