sbl

There are several "tricks" I thought I would mention that can help with cold protection. Insulation of course is one of the first things we can do, but trapping the "heat" is another. There are several things we can do--adding any form of thermal mass is helpful--rocks, bricks, bags of dirt will help, but buckets of water is even better. When water freezes, it has to release heat to the surrounding air--over 80 calories per gram.

Adding any heat source will also help--anything like a heat tape, Christmas tree lights, or a plain light bulb (just make sure it can't start a fire).

Natural sources of heat in the form of radiation comes from the ground or any nearby walls--when possible, include as much of this heat source as possible underneath your cover. In other words, do not just put a sheet over the top and pull it tight around the trunk if you could have spread it out over the ground and weighted it down with bricks.

Spraying water on a tree is another method of cold protection, but contrary to what some people think, it is not the insulation factor, it is the freezing process--if you stop adding water, the protection will stop. So you can't just get a coat of ice on the tree and turn the water off--you have to keep it going as long as it is freezing.

john_ny

I remember the time we had snow in Pensacola. It didn't last very long, but there was enough to make a snowman, and it sure looked funny to see the palmettos covered in snow.

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TommyMacLuckie

If I put cans or whatever, containers of water in my greenhouse without a heater, they will help keep it warmer. Until they freeze if it gets to that point. Then if I don't take them out they become a hindrance, absorbing the heat before it can warm up the greenhouse.

So I'll try something like that with my heater and 100 watt bulb on. I had a 16 degree difference this morning. 23-36. It's going to get worse later this week, down into the mid teens. 16 degrees is possible, which puts my green house, at the current rate, at 29.

That is not good. Hopefully the power won't go out.

Simply Bananas

The layers of water in the p-stem will freeze and protect the core of the plant. Under 20 and its likely a solid freeze through.

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sbl

The water trick really does help--the water provides 1 calorie per gram for every degree as it cools, but then when it freezes it gives up 80 calories and the entire container of water will remain at 32 until all of the water freezes. It is common practice in a greenhouse to use barrels of water to retain heat.
I have a kidde pool full of water under my lemon tree wrappings.


It would help to dump the ice in the morning to speed the warming of the greenhouse or replace the heat storage.

jeffreyp

if you have a fenced in yard, a couple steel firepits would provide heat much like smudge pots they use in orange groves.


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Abnshrek

I like the heat tapes :^) they work pretty good.. you only need the 12ft. unless you have a monster banana.. like a saba

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sbl

With the cold we are having now we need every trick in the book at the same time.

My problem is I have more plants to protect than I have protection for--so for the few that have minimal protection--they are probably goners. My best protection is all 3--wrapping, adding thermal mass, and an alternate heat source (Christmas lights). The wrapping slows down the cooling, the additional thermal mass increases the amount of cooling needed to cause freezing plus the additional heat is more easily stored.

Patty in Wisc

The other day on news, they showed farmers in SE spraying water on the trees but I didn't know they have to keep spraying. I thought it was just a one time spray but if they spray all night, wouldn't that make for a gigantic ice rink?! Good luck BTW

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sbl

Patty, in your area it probably would, but in most areas where water spray is used, the ground is not frozen and the excess just goes into the ground. The water spray is often only needed for a few hours while the temp is below freezing.

saltydad

Here's an interesting column from Heronswood Nursery.

The dog didn’t seem to be cold. I wasn’t either, but it was no warmer than —15°F. It was a clear, still night; we had gone out for a walk before bed and nothing much seemed to be moving. The only sound I was aware of was the brittle, dry snow crunching beneath our feet. As we came to the corner, under the street light, I saw a puddle of water, unfrozen. I wondered at it and reflexively kicked a dusting of snow into it. It froze almost instantaneously from the points of contact with the snow.
Why the puddle was unfrozen in the first place I don’t know. The temperature had been well below freezing for a week or more, so the puddle must have existed for that long anyway. On first glance, freezing water seems like the simplest thing in the world. But a closer look exposes more complexity. The same is true with the interaction of plants and freezing temperatures.
During the course of the year, plants from temperate regions change in their capacity to tolerate and survive freezing temperatures. Very few herbaceous plants can tolerate low temperatures for long; some have little or no tolerance at all. But after a period of cold acclimation, some perennial species are extraordinarily tolerant. Trees native to the boreal zone withstand temperatures of –40°F for months and in midwinter survive temperatures lower than that. But even species that are quite cold hardy in midwinter can be damaged by frost during their growing season.
Everybody knows that ice melts above 32°F. What’s less well known is that pure water (not rain water or tap water) is unlikely to freeze at temperatures much warmer than —40°F; the attribute of water to remain liquid at temperatures well below the freezing point is called “supercooling”. When water freezes, it becomes crystalline, but this transition does not usually occur spontaneously at temperatures warmer than —40°F. A germ or seed that initiates or “nucleates” ice crystal formation and from which crystals grow is required. This is how the snow triggered the puddle to freeze on my walk.
“Ice nucleators” are important, if not essential, in the formation of snow and rain, and they are ubiquitous in the atmosphere. Most are bacteria; a diverse range of bacterial species presumably deposited by snow can be isolated from high mountain peaks that would otherwise seem sterile. Air-borne dust also plays a role in ice nucleation, and some plant constituents are ice nucleators. Water in nature has an abundance of ice nucleators, and so it generally freezes at or slightly below 32°F.
Most plants, even very tender ones, have some tolerance for cold temperatures, and for most, frost during their growing season is a real possibility. Think of northern orchard crops, apples or cherries, whose flowers are frozen (and possibly killed) in a late frost. Global warming notwithstanding, it’s not at all uncommon in the Upper Midwest where I’m from to see frost every month of the year. Across the Sun Belt, citrus growers routinely face frost as their crops ripen.
Most plants normally supercool to a few degrees below 32°F, but generally ice nucleators cover plant surfaces—leaves, stems, flowers—and initiate freezing. On clear, windless nights, heat loss into the open skies causes plants and other objects to become colder than the surrounding air. The air temperature may never dip below 32°F, but temperatures of leaves and the soil surface may fall below freezing and ice nucleators initiate freezing (radiation frost).
If moisture is present on a plant surface and there is an entry point (a wound, a broken epidermal hair, or a stomate), ice can form and propagate within the plant’s intercellular spaces. Ice crystals within cells are always lethal. But that’s not how damage is generally caused by frost, and the ability of a plant to adapt to seasonal cold plays no part. Instead, ice in the intercellular spaces causes water to flow out of the neighboring living cells into the intercellular spaces where it too freezes. As the amount of intercellular ice increases, more and more water flows out of cells. Ultimately, dehydration rather than freezing per se injures or kills the plant.
Many woody plants are not much susceptible to this sort of frost damage. Yews and oaks are examples. Research indicates that morphological features such as thick, waxy cuticles act as barriers to ice nucleation and propagation in these plants. In some plants, the propagation of intercellular ice is blocked from entering tender lateral shoots or blossoms. There has been some success on an experimental basis spraying hydrophobic particle films on the surface of tomato plants, which are tender and can be killed by frost, to block ice nucleation. But the current procedure is probably not worthwhile on a commercial basis and impractical for a home garden.
An obvious practical approach a gardener can take is to be sure that plants are well watered before a period of expected frost. Having fully turgid, nonstressed plants may prevent killing cellular dehydration that can accompany a growing-season frost. In the cranberry bogs of New England and Wisconsin, when there is threat of frost, commercial growers continuously apply water to cranberry vines with sprinklers. The rationale behind this is that as water freezes, heat is released. This is what is known as the “latent heat of fusion”, and it is enough to keep the vines from freezing. Citrus growers avoid allowing cool air to pool by keeping air moving with giant fans.
As days grow shorter and nights colder, annual herbaceous plants senesce and die, but perennial plants that are adapted to the temperate and boreal zones enter a period of dormancy and begin to acclimate to the cooler and ultimately freezing temperatures that a month or so earlier might have killed them. Despite 100 years of study, our understanding of how plants perceive low temperatures and respond by regulating gene expression and metabolism is incomplete. This is not too surprising really since cold adaptation is an exceeding complex trait that is controlled by a myriad of genes that in turn are influenced by a myriad of factors, and it is nearly impossible to model adequately.
The concept of “cold adaptation” is implicitly presented as if it were a unique, one-time event. This of course is a grand oversimplification. The climate in winter is no more stable than it is in summer. Winter begins on a particular calendar date, but cold temperatures do not usually conform. There are periods of intense cold, followed by warming trends, followed by intense cold. Plants experience these events and respond to them. In midwinter, a warming trend may induce a plant to partially deacclimate, but the next week the same plant may be subjected to intense cold. To survive, it must reacclimate.
In a purely descriptive simplistic sense, as a woody plant adapts to cold, water is flushed out of the cells to the intercellular spaces, where it freezes, and water further flows out in response to the intercellular ice. The composition of fats and proteins in the increasingly permeable cell membrane changes, and salts, sugars, and proteins are synthesized that are concentrated in the living cells and increase the solute concentration, acting as “antifreeze”. Freezing and killing dehydration do not occur.
The ability to maintain this state, where intercellular water is frozen but the adjacent cells remain viable and intracellular ice nucleation is suppressed at very low temperatures is called “deep supercooling”. What allows small quantities of water within cells to avoid freezing, despite the proximity of extracellular ice and low temperature, is poorly understood. The ability to supercool seems to be related to the cell wall structure and composition, but there are also adaptive features that must be under genetic control.
Over the last two decades, increasingly sophisticated molecular biology techniques have been developed for plants. More and more these tools have been applied to teasing apart the genes and their roles in cold acclimation of the weedy species Arabidopsis, the fruit fly of plants. Lots of progress has been made. But from an anthropomorphized view of evolution, the goals of Arabidopsis are quite different from those of woody temperate plants, and Arabidopsis has the capacity to survive only a few degrees of cooling below freezing. The knowledge gained from Arabidopsis will certainly aid in breeding more frost tolerant plants and crops, but understanding cold adaptation and deep supercooling may remain elusive.

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sbl

Understanding radiative heat is one of the keys to freeze protection. I could not understand how we could get frost when it was not freezing until I understood radiative cooling. All matter radiates--that is what we see with infrared cameras and sensors. That radiation is a loss of energy (heat), but they are also recieving radiation from all matter around it--that is one reason why adding things like rocks and bricks around you plants will help. The bucket of water has an additional benefit of giving off heat as it freezes--the "heat of fusion" you mentioned--about 80 cal per gram.

The other factor here is trapping that radiative heat--it is one of the reasons that plastic does not do much to protect plants--the infrared radiation goes right thru. Sheets or burlap are much better at trapping that radiative heat that comes from the ground.

jeffreyp

If you have small plants you can cover them with sheets from your bed, blankets etc. Banana stems you can wrap with beach towels which also helps. I think if I was in north florida with a small/medium sized yard i'd try the fire pit method and maybe a box fan to blow the warm air around.

jwmahloch

I have my windmill palms covered with umbrella greenhouses, inside each one I have a 45 watt halogen light and 15 feet of pipe heat cable wraped around the truck on the ground (the temp sensor mus be outside the umbrella greenhouse and not covered up with dirt or mulch. I also have them covered with blankets. It will stay 20 to 25 degrees warmer inside depending on the outside temp. When I got home today it was 27 outside and 47 inside the umbrella greenhouses. This morning it was 11 outside and 34 in the umbrella greenhouses. It helps that I have a wireless temp sensor inside one of them and the thermomitor in my kitchen. The min temp so far this winter inside the umbrella greenhouses has been 26 degrees and the min temp outside was 2 a couple days ago.

Freeze pruf also helps add about 5 degrees of cold tolerance to most plants. It works better on palms than on banana plants from my experience. It needs to be reapplied every 4 weeks and its supposed to be above 50 when you spray it on. It has not been above 50 in st louis for about a month now and I need to apply again. I am waiting for a mild days but it seems to be staying cold. Now we are supposed to get 6 inches of snow here tonight. Snow is actually supposed to be good insulation for plants from what I have read.

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Nicolas Naranja

I'm getting a real kick out of the local weathermen saying that there is a chance for snow...IN SOUTH FLORIDA

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aroidgrower

I am in zone 6 Kentucky and I have had Basjoo and other tropical plants outside for over 20 years. The main trick I use is the heat from rotting organic matter. I normally use a thick layer of leaves and grass around the base or over most of my beds. The beds are actually one giant compost pile and adding fertilizer helps speed and heat up the process. On average I can gain 1 to possibly 2 zones from this method. I have also been adding clear old greenhouse plastic over the beds that have leaves. This works well also because as we stay below freezing for a week or more at a time the freezing temps creep deeper and deeper closer to the plants. But if you have clear or black plastic or other dark material on the beds the sun heats them up above 32F and they thaw out. They may freeze again at night but they do not penetrate as deep as they would with out it.

ewitte

I did this to my bananas right before the snow on December 4th. Last night I added towels around the base. Will leave the towels until ~ Sunday and pull them off. Also two of the three plants are on the patio. I'm leaving the patio light (70watt HPS) on.