Frank, You are NOT going to have your figs "in hard dormancy" between 33 and 40 degrees. You do not have to protect them from freezing - lower temps are what keep them in deep dormancy.
Put a thermometer in the shed and check it before the sun hits it in the morning. That will give you an idea how cold it got overnight. If it stays above 15 degrees, your figs should be fine. By heating them you will be keeping them in light dormancy, and if your heating system fails, they will be much more likely to be damaged by temperatures that they could handle in hard dormancy.
If you find the temperatures in the shed are too low, insulate the trees.

effdeevee,
That is good advice given to you buy fignut. I have had some years of experiance storing my figs in an unheated and not insulated garden shed and I'm in zone 5. I used to wrap just the tops with several layers of blankets and they kept well stored like that in my shed untill seceral years ago when we received two weeks of very low temptures even for this area.

That was the year I lost all nine of my trees to the cold in my shed. I often wonder if I would have wraped the containers as well with insulation and also covered the top of them if my fig trees would have made it. For the last number of years I have move them from the shed to my garage which is attached to my home but is also not insulated.

So far over the years the trees have held up fantastically
and a few years ago we did get extremely low tempsd for days. I still don't wrap the containers I just tie and cover the trees real well.

I have a friend who lives near me who has a shed as well but his shed has one skylight window in the roof. He does not cover his trees at all but he does have a small electric heater that he has sets to come on at 19 degrees
and turn off at 22 degress. He has never lost a tree to the cold. His shed is also insultaed and has a cement floor
which may add something on sunny days.
For what it's worth.
Lou NE., PA

miracles do happen but figs kept @ 19*F= (-7* Celsius)will freeze ? At minus (-7*C) will become total ice.

The primary trigger for the onset of dormancy in F carica is decreasing photoperiod. Technically, it is increasing periods of darkness, but since that is always accompanied by decreasing photoperiod, we'll leave it at that. Dormancy deepens with chill, but figs pass through dormancy VERY quickly. They are dormant for short periods - like 100-200 chill units. The best temperatures for accumulating chill is from about 32-40* F. Below 32*, no chill units accumulate. After a short dormancy, they pass into a period of quiescence, during which they are capable of growth as soon as soil temperatures allow.

You cannot keep trees in "deep" or "hard" dormancy unless you happen to find the trees in true dormancy and lower the temperatures below 32* so no chill units accumulate, so we can say with some sureness that we cannot keep trees dormant for long (only a few days), only in a quiescent state. We can guarantee quiescence by keeping the trees above killing low temperatures and below about 45*. After soils warm to 45*+, for more than a few days, the onset of growth will occur.

I think it's probably unlikely that your trees would see killing lows in your zone and in the shed, unless the shed is so full of openings for the wind to penetrate that it affords little night protection. Here is some information about how cold affects soil and plant that I left on this forum a year ago. Perhaps you can apply some of it to your situation/conditions:

"Commonly, each species of plant has a general range of cold-hardiness, but we know this does not apply to F. carica. Within species and cultivar, cold-hardiness is genetically determined. That is to say that a plant that is propagated from cuttings or tissue culture will have the same ability to resist cold as the parent plant. Plants cannot "develop" a greater degree of cold-hardiness by repeated or prolonged exposure to cold, even after 100 years (trees).

If we pick any plant at random, it may or may not be able to withstand freezing temperatures. The determining factor is the plants ability to prevent freezing of bound water. Bound water is the water inside of cells.

There are actually three kinds of water to consider when we discuss "freezing". The water held in soil - When this water freezes, and it can freeze the soil mass solid, it doesn't necessarily kill the plant or tissues. Then there is free or unbound water, also called inter-cellular water. This is water that is found in plant tissues, but is outside of living cells cells. This water can also freeze solid and not kill the plant. The final type of water is bound water or intra-cellular water. If temperatures drop low enough to freeze this water, the cell/tissue/plant dies. This is the freeze damage that kills plants.

Fortunately, nature has an antifreeze. Even though temperatures drop well below freezing, all plants don't die. In hardy plants, physiological changes occur as temperatures drop. The plant moves solutes (sugars, salts, starches) into cells and moves water out of cells to inter-cellular spaces in tissues. These solutes act as antifreeze, allowing water in cells to remain liquid to sometimes extremely low temperatures. The above is a description of super-cooling in plants. Some plants even take advantage of another process to withstand very low temps called intra-cellular dehydration.

The roots of your trees can stay frozen for extended periods or go through multiple freeze/thaw cycles w/o damage, so long as the temperature does not fall below that required to freeze intra-cellular water. If roots remain frozen, but temperatures remain above killing lows, dessication is the primary concern. If the tree is able to take up water, but temperatures are too low for the tree to grow and make food, stored energy becomes the critical issue. Dormant and quiescent trees are still using energy from their reserves (like a drain on a battery). If those reserves are depleted before the tree can produce photosynthesizing mass, the organism dies.

There are a number of factors that have some affect on the cold-hardiness of individual plants, some of which are length of exposure to seasonal cold, water availability (drought stressed plants are more cold tolerant), how recently planted/repotted, etc."

Al

FF members: ...thanks all, for the quick answers to my questions re: heating my unheated garden shed. I was relieved to learn that my figs will probably survive the harsh winter temp.s with little, if any, problems.

I was really concerned about winter-kill in so cold an enviroment, but according to you guys, I should give my worries a rest. I would really like to continue to grow my fig trees from season to season, and as I've mentioned, the unheated shed is the only area I have for overwintering my fig trees.

Thanks again for all your help, and suggestions with my questions, and especially for educating me once again. I'm always amazed at how little I know.

Heat costs money, regardless of the source. Some sources are more efficient, delivering more heat (BTUs) per $, but it still costs money. Adding insulation cuts the heat loss, which reduces the need to input heat, and thus saves money. No way around it.

pezzuti9
You are in Zone5. I am also in zone 5 and my garage which is attached to my home is also not insulated and not heated. Similar zones may experience similar avergae minimum temperatures but may differ as far as lowest temerature swings are concerned. What lowest tempeatures do you get in your zone 5 area in January and February? Some years in January or February we get a few days between -25F and -30F at night in Ottawa.
Next year I am planning also to experiment inside the unheated un-insulated garage with some plastic enclsure, just large enough for my few fig plants, attached to the house wall where the heat loss from the wall may be trapped to keep a decent temperature for figs to survive. It may require a watch between mid-January to mid-February for the nasty low temperatures. Any comments?

Hello tapla
Is it possible to put approximate numerical values (or ranges) for the two freezing temperaures as far as common figs are concerned i.e. for "unbound water or inter-cellular water" and "the bound water or intra-cellular water"?

No one can give a definitive answer that even comes close to accurately assessing the temperature at which bound water will freeze that covers the whole species. Unbound water is of little concern & will usually freeze somewhere around 28*.

Some material will be able to withstand little cold & roots could freeze/die at (actual) root temperatures as warm as 25-27*. Other plants may tolerate much colder actual root temperatures - as low as 10*. There's just no way of knowing unless you have a feeling for how cold-tolerant the genetic material the plant was derived from might be, and finding out is expensive (from the plant's perspective). ;o) Another example of this genetic variance is that trees found growing and fruiting well closer to the equator need no chill time, while other trees, derived of genetic stock from a more northerly provenance may need a period of chill to grow with optimum vitality in the subsequent growth period/cycle.

Another tree that fits the same mold as Ficus c. is Ulmus parvifolia (Chinese elm). It varies over an extremely wide range in cold tolerance and chill requirements.

It's wise to remember that root death isn't instantaneous at one particular temperature. Roots succumb to cold over a range of chill with cultural conditions affecting the process. The finest roots will die first, and the slightly thicker and more lignified roots will follow, with the last of the roots to succumb being the more perennial and thickest roots.

Since any root death is a setback from an energy allocation perspective, and root regeneration takes valuable time, it's probably best to keep actual root temperatures in the 25-45* range as long as we can when the tree is resting, even though the organism as a whole could tolerate much lower temperatures. Even well established trees become very much like cuttings if all but the roots essential to keep the tree viable are lost to cold. Regeneration of roots is an expensive energy outlay and causes the trees to leaf out later than they normally would and shortens the natural growth period.

Al

Dear FF Members :

Today the temp.s soared and reached into the mid-50s. It felt just like Spring. I decided to take a look at the "ATREANO" fig trees that I'm storing in my unheated shed. I expected to see dried-out shriveled terminal ends to all the branchlets, however, I was encouraged when I saw that the branch tips showed green terminal buds, and green under the bark when I scratched away at the top layer with my fingernail! Now, I really can't wait for the warmer weather to break so I can see if my trees really did survive this winter. Judging by what I have seen so far, I am ever hopeful that the figs will be growing again in a few short months.

Maybe I was concerned and worried about the condition of my trees for nothing. I'll keep you guys posted.

Thanks again, Frank DV...from, DA-BRONX