I think the more important issue is the repotting method. If you can't loosen the root mass/growing mix your tree is in trouble (over any kind of long-term. Potting up without bare-rooting doesn't buy you much help.

I have received and bare-rooted many trees which were done like this. The next time you repot, the new material you added may shake loose pretty easily, but the core (the boundaries of your old container) will be rock hard. As the roots in the core continue to constrict themselves, they prevent the flow of water/minerals up into the tree. Basically, the tree strangles itself to death.

You didn't mention how big the former container was. My guess is you could probably put the tree back into it and leave it for the rest of this season then bare root and repot the tree sometime before bud break next season and be okay. This would make over-wintering this year more bearable.

Hi, DL. I'm not quibbling about terms, but it sounds like you only 'potted up', which is quite different from a repot, which includes removing all or almost all of the soil and root work. I agree with James - I think your tree's roots are in dire need of attention come spring. There are lots of posts about repotting methods - James has posted a good one, and I'm sure I've left a description that parallels his on this and other forums, so you might wish to have a look around for it.

Your question more closely asks what temperatures will my tree tolerate, but it leaves unanswered the question of what temps are best. It would be best if you could keep actual soil temperatures above 25 and below 42* for the winter. Here is a longer explanation about cold-hardiness I left on this forum previously. If it leaves you with questions, just ask:

Commonly, each species of plant has a general range of cold-hardiness. 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

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.

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 25-40* 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 and reduces the potential increase in biomass for the next growth cycle and perhaps beyond.

Al

Thanks bjs496 and Al,

I did in fact pot-up -not- re-pot as I posted. The tree was in a 14 gallon container and I potted-up to 18 gallons. In 2009 I did a full re-pot on this same fig because it began to outgrow the 10 gallon container in August or September. At that time I was able to free all of the roots and refresh the potting medium as described in a post on this forum. This same fig had a full re-pot in early May of 2009 also. This particular fig sends roots up and over the edge of the container. Seems like I have not learned the growth habits of this particular fig. I have read that some in-ground figs will grow like a weed and take over a yard. I have neighbors who complain that they can not kill their fig tree. I think this Colasanti is such a fig. I will take some cuttings and root them - just in case I have begun the death of this fig. The figs this tree puts out are super sweet and flavorful.

Thanks for all help.

DL

I mention often how vigorous (genetically) figs are in comparison with most other trees. They grow like crazzy, quickly getting root bound! I also have the same issues with the mulberries I have in containers. Same family as Ficus (Moraceae) and very close relative of figs. Sounds like you have things under control. ;o) Good luck!

Al

question for Al, you have mulberry tree in a pot, what size pot? my son planted a mulberry tree in the ground and was told by landscaper to remove it because its too close to the house, he was also told he could not put it in a pot, last spring he had fruits to enjoy so he really does not want to get rid of the tree, so in your opinion a mulberry tree can be grown in a container. he lives in tucson.i realize this is a fig forum sorry if this subject is not a fig question, thanks

As noted, figs & mulberry are very close relatives and about equal in vigor, so almost anything said about mulberry could be applied to figs, and we all know that with proper attention, they do very well in containers.

I have them in pots about 5 x 8", and one a little larger. Lol - they are now in bonsai training pots, but I grew one out to a 2" trunk caliper in the ground, and the other to that caliper in a 3 gallon nursery container.

With proper attention to roots, you CAN maintain robust trees with large caliper trunks in rather small volumes of soil.

Al