Frost/Freeze damage to Plumerias in California

I live in Southern California. We have had record low tempratures over the last five days. All my plumerias are in pots so I was able to bring them inside to protect from cold tempratures. I was wondering how plumerias planted in the ground are faring after the big freeze here in California. I have thought about planting in the ground, but am not so sure about it now. What has your experience been?

Hi Lorien,

It got down to 28 for several hours the night before last. There are many, many plumeria trees planted all over Southern California, and nearly all openly exposed trees experienced some freeze burn to the leaves, depending upon where they are located and how cold it got. This cold spell is very unusual and hasn't happened before. Some got some tip damage too.

All the trees planted in Zone 10 should come back just fine. Since you are in Zone 10, you can definitely plant them in the ground. You will just have to do what I did and cover with a blanket or tarp when this kind of thing happens. You can put a space heater underneath the tarp for added warmth as well as I did. There are also portable greenhouses that can fit right over the top of plumeria trees that some members used. I have a portable greenhouse set up with a heater inside for all my very special ones that I need to be protected.

There are many pictures of damage being posted over at PlumeriaPals. Here is one member's pics named Dewaine:

http://pictures.aol.com/ap/singleImage.do?pid=7150ANQHQwQQS2f9KSeZtIW-XJRsOXKI*ElYv4xQp5Fd3Ig%3D
http://pictures.aol.com/ap/singleImage.do?pid=7150ANQHQwQQS2f9KSeZtIW-XGGnD126abm5v4xQp5Fd3Ig%3D
http://pictures.aol.com/ap/singleImage.do?pid=7150ANQHQwQQS2f9KSeZtIW-XCxfYs0hhPZgv4xQp5Fd3Ig%3D
http://pictures.aol.com/ap/singleImage.do?pid=7150ANQHQwQQS2f9KSeZtIW-XGvQWoVd-4xIv4xQp5Fd3Ig%3D

The burned leaves should drop off and are not really a sign of real damage, I don't think. As long as the tips are not black or mushy, they should be fine.

Many brugmansias were seriously damaged as well as other tropicals here in Southern Cal. The brug forum has some pictures of damage.

This message was edited Feb 21, 2008 1:07 PM

Here's a link showing brugmansia damage pics here in Southern California, including my damaged brugs: http://davesgarden.com/forums/t/684223/

Here's a picture of my greenhouse:

I'm worried about the big one you helped me save, Clare, it doesn't look so good. It's bigger and extends out beneath the eaves but I'll keep babying it. The others look good. I'm broken hearted about an impatiens my mom had bought me that was frozen. The garden hose was frozen, the dogs water bowl as well as the bird bath were frozen over. This is despicable! (sp)

Oh my that frost damage is sad :(( The morning news said we were the warmest in the Country today ! It's been in the 80's. Hope you all have no more frost just Sunny warm days !

Louise, it must have gotten really cold where you are for a long period of time. Did you check to see how low it got? It got down to 28 here for several hours. They say that 28 and below for two hours or longer is considered a hard freeze. So sorry about your impatiens. I'm hoping your plumie will come back just fine, but it may need a little pruning if the tip turns black or mushy. Try to surround it with as much heat as possible and don't let it go bone dry. A dry plant will experience more frost damage than a well-watered one so I'm told.

Thanks, Violet! Yeah, Florida is the place to be right now.

I'm sorry to hear about all your losses. Good luck for tonight.
Mickey

Thanks, Mickey! I wish I had an Arizona room like you do right about now!

I can't imagine how difficult this is for those of you who never see weather like this. Back when we used to have frosts it was always so scary. I am not sure if I should be thankful we don't have frosts anymore; the weather is just flukey nowadays. Still in the high 60's here and although that cold front is coming we are only supposed to get into the 50's, and the 40's at night.

The folks on the Palms and Cycads forum have reported significant damage; so sad.

I agree, Alice. Some people got hit really hard, and it is so sad.

Clare it's still getting very cold here and no I didn't check the temps when my plants froze but when I got up that morning my thermometer said 20. Supposed to be in the 30's tonite but I think my plumeria are ok...will get to watering them today, with the winds we had, everything is so dry. Alot of dead things too but they will be replaced, all except the impatiens I lost from my mom. My fault, forgot to move it under cover. Maybe she'll buy me a new one!
Thanks again Clare.

Hi Louise, the winds are really blowing here too, but that seems to have made the temps warmer. It didn't get below 50 here last night. It is predicted to be 33 here tonight. I watered everything yesterday too because the winds made everything so dry. I'm so sorry about your impatiens but glad your plumies will be all right.

This article was just posted on another forum and may be helpful:


***************************************copy and paste follows ****************************************************
FROST PROTECTION

It’s hard to believe that late in Oct of 2003 we faced 100° days, and now 3 weeks later, we’re bracing for frost season! For the past 20 years the coldest temperatures in Phoenix have occurred around Thanksgiving when frost damage is usually most severe.

There are many misconceptions about how frost actually damages a plant. It is incorrectly assumed that ice forms inside cells causing them to rupture and burst open when they freeze. This never happens. When people first examined frost damaged plant cells under the microscope in the 1930’s, they never found any burst cells. Cells from damaged tissue were always dehydrated and wilted but their cellular membranes were intact and never torn open. The so called, “Rupture Theory”, was proven false in the 1930’s but the notion continues to this day.

It just so happens that freezing damage is a wilting process that is identical to dehydration damage. But how does wilting occur as plants are frozen?

The surprising clue came from a citrus orchard in Israel where farmers were spraying their trees with tetracycline to control a bacterial disease. Half way through the orchard they ran out of spray and couldn’t finish spraying the crop. Later that night the temperature dropped to 25° F and severe frost damage occurred on the trees that weren’t sprayed. But to the farmers’ astonishment the trees sprayed with the antibiotic did not have any frost damage. How could an antibiotic be a frost protectant? It did not make sense. What was the link?

After much study it was discovered that the antibiotic prevented ice crystals from forming on leaf surfaces. How? To the surprise of everyone it was shown that the antibiotic suppressed bacteria that caused ice crystals to form. These ice-nucleation bacteria triggered ice crystals to form that caused the frost damage. If ice didn’t form, there was no frost damage, in spite of the cold temperatures being the same.

The key to surviving freezing damage was to maintain water in a liquid state, even if temperatures dropped below 32° F, the known freezing point of water. Water that stays liquid, even when its temperature drops below 32° F, is called super cooling. As the Israeli’s found out, anything that promotes super cooling may protect plants against freezing injury.

How is super cooling achieved in nature? One thing is leaf cleanliness. Ice crystals form on dusty or dirty leaves more quickly than on clean leaves. This occurred in the Israeli orchard. Another treatment is to spray leaf surfaces with a sugar or glycerol solution. The sugar dissolves in dew on leaf surfaces and lowers the freezing point of the dew by several degrees. Under the right conditions this is just enough to protect the leaves from freezing damage.

Plants that are naturally frost tolerant use this strategy by making excess sugars or proteins to lower their freezing point. Freezing tolerant plants also tend to have smaller leaves and produce smaller cells as day length’s shorten. The small cells increase surface area and making it more difficult for ice to form. This explains why tropical plants have difficulty protecting themselves from frost. Unlike temperate zone plants, tropical plants can’t distinguish long from short days.

Tropical plants tend keep their leaves and produce large cells year round. Gardeners can control cell size with fertilizer and water applications. Frequent fertilizer and water will promote large cell size that is more apt to freeze. Thus, the traditional practice of “hardening plants” to protect from frost injury is based on sound scientific principles. Cutting back on water and fertilizer increases sugar content that reduces ice crystal formation.

Hardening is one approach to protecting plants from freezing temperatures. The other is to modify the microclimate around the plants. How? By adding heat when temperatures are low. How is this done? Homeowners do this by covering their plants at night to trap heat and prevent it from escaping to the surrounding air. Blankets, towels, sheets, plastic tarps all work. Another procedure is to string light bulbs in the trees. High wattage bulbs generate more heat. This should only be done on the night frost is threatening, not before or after. Infared heat lamps may also work from a greater distance than incandescent bulbs. Fluorescent bulbs do not work well because they emit less heat. Remember that the radiant energy from light travels in a straight line and that trees in shadows will not be protected. Be sure that light surrounds the tree or else the shadowed side could be damaged. Farmers have traditionally added heat to save their orchards by burning smudge pots or spraying huge amounts of water to their trees during the actual frost. Homeowners should avoid sprinkler irrigation of trees where light bulbs have been strung up. The electrocution hazard is real. Farmers also occasionally use wind machines or helicopters to mix the hot air that sits above the cold air during a temperature inversion. Of course this procedure is impractical for residential homeowners.

The extent of frost damage on trees is dependent on the temperature reached, and the duration of the low temperature. Conditions that favor large versus small ice crystal formation cause the most severe frost damage. For example, four hours at 28° F can be more damaging than one hour at 23° F. Also, freezing damage depends on the plant with each species having its own “killing” temperature. The most sensitive are tropical evergreen plants with large leaves. These can be killed by temperatures as high as 40° by a process known as chilling injury. For most tropical plants, however, the killing temperature is between 32-28° F. The next most sensitive groups are the broad-leaf, semi-tropical evergreens. These include eucalyptus, citrus and Ficus that are killed by temperatures between 32-18° F. The succulents, that include cactus, agave and yucca’s have killing temperatures between 28-5° F, depending on species and their acclimatization. The next group on the list are deciduous trees and shrubs with killing temperatures between 20° F down to -40° F depending on species and their acclimatization. The most frost hearty group are some of the temperate zone conifers, which can survive bone chilling temperatures down to -70° F in the most extreme alpine and arctic conditions.

Although we in Arizona don’t have to face frosts every year they can cause severe and costly damage to trees that large trees that managed to escape damage during the mild years.

Clare, thanks for the information regarding Plumerias and frost. Hopefully this cold snap is on its way out (Though I did hear that it snowed in the Santa Monica Mountains today).