You should be fine, Rob. The gritty mix holds less water than heavier peat-based soils, but that's a good thing in winter. Besides, you'll be surprised at how much water the soil holds and for how long. I generally only throw a little snow on my over-wintering trees (in the garage) 3-4 times over the entire winter. They can get quite dry - just don't let them dry out completely.

There are 2 ways to look at young tree roots. You can make a generalization and say they are more tender than the roots of older trees and thus need more protection; or, you can say they are no more tender than the roots of older trees - they just lack the more lignified and larger roots that the old trees fall back on during periods of extreme cold.

Roots don't all die at the same temps. The fine roots of large trees die at the same lows as the fine roots on small trees. The medium sized roots die at the same temperatures as well. The real issue is that the older trees can lose their fine and medium roots and still come back from the large roots, but small trees that lose fine and medium roots (at the same temps large trees lose them) are goners - because they don't HAVE the heavier roots.

The rub here is we shouldn't be letting any of our trees experience temps low enough to kill the fine and medium sized roots, just because they will 'tolerate' it. It's better to keep the temperature as close to freezing - 42* as possible, to ensure the best root survival. I see lots of people offer advice that 'figs are fine down to 'X' degrees .....' but are they really? Just because they tolerate it doesn't mean they like it.

If you're worried about low temps, set your trees on the garage floor & cover them with an overturned cardboard box. It will keep them toasty warm (by tree standards), even if you forget & leave the door open inadvertently during a cold spell.

Al

Thanks Al. There is always some new info to learn from your posts. I will apreciate answer to a couple of questions that came out of this thread.
1. How long does it take for a potted tree to get those large roots which are relatively more cold tolerant than the medium and fine roots?
2. Al mentioned "It will keep them toasty warm (by tree standards), even if you forget & leave the door open inadvertently during a cold spell.". What are the cold temperatures referred to as cold spell here. We do get -20F cold spell every year in Jan-Feb and some years as low as -30F. Is there a chance of survival of medium or large roots in an unheated garage here?
3. Will the survival chances increase in temepratures mentione above in my zone 5 if the pots are placed on cement floor in the unheated garage, surrounded by a fence-like perimeter, covered all pots together inside the fenced space under a tarp and then covered with maples leaves and then covered again with another tarp so no air gust will reach the plants?
I know I can try and find out the hard way and lose some plants. But taking a chance with some knowledge helps. I tried last winter with a coule of tree in less elaborate way. The tree survived but shooted late some times in July!

1) How long does it take for a potted tree to get those large roots which are relatively more cold tolerant than the medium and fine roots?

As with many other physiological plant processes, certain events depend more on growth rate than on a chronological time lapse, but a good indicator that roots are gaining in cold-hardiness is when the root loses the finer roots we often refer to as 'hair' roots and becomes more involved in transport of water/nutrients than assimilation. (gathering them). As the cortex (outer covering) of the roots gains a fibrous coating similar to bark, the roots are increasing in their resistance to cold. Of course, the most hardy roots will be closest to the trunk because they are the oldest, so that is another good way to determine how hardy a section of roots might be. Basically, the proximal roots that are getting or have a bark-like covering are the most hardy, and the finest distal roots the least hardy. Most cuttings, if grown well, will have mature roots by the time they are entering their 3rd winter.

2) Al mentioned "It will keep them toasty warm (by tree standards), even if you forget & leave the door open inadvertently during a cold spell." What are the cold temperatures referred to as cold spell here. We do get -20F cold spell every year in Jan-Feb and some years as low as -30F. Is there a chance of survival of medium or large roots in an unheated garage here?

Where you live, trees in the landscape have the buffering effect of the earth to help moderate soil temps during the cold snaps you describe. You'll find that even during periods of extreme cold, that your 6" soil temperatures won't fall below 25* F. The small soil volume of containerized plants offers virtually no buffering effect, and the fact that trees are often isolated from a source of extraneous heat (siting them on decks/tables/railings ....) is a consideration as well.

I think there is a chance of survival in an unheated garage if you use some care & try to take advantage of extraneous heat - that being the wall between the house & garage and the garage floor. If your garage is unattached and drafty, I don't have much hope, but if it's attached & you use boxes to keep them covered, and don't allow the door to remain open all night on the coldest of nights, it should work for you. You might try cutting the bottom & 1 side out of a box so the open side is against the wall between the house and garage. Use a digital thermometer that shows daily highs & lows to see how you're doing. They're not that expensive - around $15-20 US here.

3a) Will the survival chances increase in temperatures mentioned above in my zone 5 if the pots are placed on cement floor in the unheated garage, surrounded by a fence-like perimeter, covered all pots together inside the fenced space under a tarp and then covered with maples leaves and then covered again with another tarp so no air gust will reach the plants?

You're on to something. If you put the plants directly on the floor with some space in between, then fill the spaces with leaves and keep the whole affair corralled, it will really help to keep soil temperatures up. You can then arrange something of a tent to help guard against the bitter cold that could still kill above ground tissues, even though these are more hardy than roots. Don't cut off ALL air flow though - you don't want to introduce fungal issues with your set-up. DO be careful that temperatures don't get TOO high & start the plant to growing during a Jan thaw. That would be decidedly bad. ;o)

3b) I know I can try and find out the hard way and lose some plants. But taking a chance with some knowledge helps. I tried last winter with a couple of tree in less elaborate way. The tree survived but shooted late some times in July!

I've talked about this often when debating cold-hardiness of figs and other trees. You can see that your trees tolerate very cold temperatures to the degree you noted, but they assuredly don't like it. When (the collective) you adopt the idea that it must be OK to over-winter my trees where they will be subject to temperatures in the teens, you miss an important part of the picture. Yes, the tree survived, but essentially you've reduced the tree to something like a large cutting. The tree HAS to use energy reserves to grow an almost entirely new root system before it can go about it's above-ground business of making leaves and fruit, and getting fat. This is a large and unnecessary setback for the tree. If you think about it, a loss of potential doesn't just affect a tree in the present, it has a significant effect on the tree forever. You (your trees) can never regain lost potential - they can't catch up.

Al

How long do your cold spells last? We can get down to 20 below (F), but it rarely lasts for more than 4-5 days. Normally, down into the 20's is most of the weather.

So the plan here is to put an oil filled radiator in the garage with a thermostat that turns it on as the air hits freezing.

I don't think our garage has ever frozen, but it is attached to the house and has a dog door from the house to the garage to let heat seep into the garage. The dog door from the garage to the outside has baffles, so it doesn't let all that much cold air in.

Besides the baby fig trees, the garage is going to contain pears and apples (fruit, not trees)that I don't want to lose to freezing. So a week or two of running heat at night isn't too much to pay.

Let me ask another question, what is the warmest temperature a dormant fig tree can be held at? I have an unheated sun porch that may get up into the 50's on a sunny day, bad for dormancy?

Temperatures above 42* for more than a day or two can stimulate growth. At that point, cold hardiness is diminished considerably, so the tree shouldn't be subjected to freezing temps after initiation of growth. The buds will be the least hardy (after initiation of growth) of the above-ground organs. The tree will still go into a kind of suspended animation and stop growing (above the soil line) if the temperature drops back down to 32-42* after bud movement.

Al

Al - based on your last post re max temperature for overwintering - I dont have any place to keep temps under 42F. Even our unheated basement keeps temps around 50F. I am thinking to keep my 2 yound figs outdoor, in pots, sunk into the ground - where they spent the spring and summer. They by the porch, facing east and towards south end of porch, should not get too much wind. If I just cover them with leaves and burlap, do you see any risk of them dying?
Thanks

I would bury them on the north side of a heated building against the foundation and mulch heavily. It's possible the top(s) will die back if you get the lows you could see in USDA 7a, but if you can see your way clear to follow my suggestion, it's very unlikely the roots will freeze. No chance you can over-winter in a garage or out-building that's not too drafty?

Al

no garage, we chose to spent money on a full size basement.

We have a small tool shed but it is pretty stuffed with car parts, garden tools, and a whole motorcycle. And there is no light in it. So would I have to open the door once in a while?

My North facing wall option - do I bury just the root section and leave trunk above ground and then mulch? Do I need to wrap in burlap or blanket? That wall gets almost no sun at all - the roof casts a foot of shade and there are lots of large trees around

So would I have to open the door once in a while?

No. While evergreens are capable of carrying on some small amount of photosynthesis when they are cold but above freezing, deciduous trees are not. Light becomes important again after the onset of growth subsequent to dormancy and quiescence (the temperature-induced rest period after the dormancy chill requirement has been met).

My North facing wall option - do I bury just the root section and leave trunk above ground and then mulch? Do I need to wrap in burlap or blanket? That wall gets almost no sun at all - the roof casts a foot of shade and there are lots of large trees around.

You can actually bury the tree as deep as you want for the winter and lift it in the spring. If you had a big enough hole, you could actually bury the entire tree & dig it up when it warms in the spring. Perhaps you could bury it diagonally and cover the top loosely with a box or trash can (you need some air circulation). It doesn't help to wrap the tree in cloth or burlap from the perspective of temperature, but it does help to reduce damage from dessication.

Shade is a friend of dormant trees. It helps prevent sap from rising and freezing, killing all or sections of the trunk. It also keeps the roots cooler longer into spring, so there is less danger of frost damage.

Al

Is there any advantage to keeping a tree covered with black plastic during dormancy to keep out light?

thanks, Rob

No - it's sort of like when you're out like a light right before surgery - you don't really care if it's the weird guy with orange socks and mustard in both eyebrows who's shaving your stomach for the appendectomy. You're like, counting backward from ten and wondering how he got that mustar .........

Al

Yes Al been there in room couting on several occasions and woke up and forgot what number i made it too !!!
Best Health
Martin

My husband thinks we can put them in basement when it gets colder. The trees still have green leaves on. Do I wait until they drop all leaves / start to yellow and drop leaves to put them inside? Do I need to fertilize them now or then?

What happened to burying and mulching? How about the rest of you guys near Richmond - is that a viable option?

Al

My first post on this forum!!! This has been a very informative thread. I find myself in the same situation as others who just don't really know what to do. I am i bit apprehensive with the idea of leaving my baby fig tree in an unheated garage over winter. I have know idea how much warmer it stays on average in the garage versus just being outside. Does anyone have a past experience of estimating what the temp difference is between outside and an attached unheated garage? As another poster said I hate to try something only to learn the hard way. originally i thought the basement would be cool enough but as i've read it seems i need to drop below at least 42 degrees for a proper dormancy, but for how long?

I like the idea of constructing a protective barrier in the garage although i have no room for anything very elaborate. There must be a reliable way of keeping something at just the right temp taking into consideration that we can have temp extremes as low as -20F and as high as 40F whenever old man winter decides. It just seems like there is such a large amount of variation in possible temps that I would have to constantly monitor the trees temp and make necassary adjustments to the heat source, but what do i do when i have to travel out of town for a week and the arctic cold front comes through while i'm away?

I moved my tree to the basement today because we had our first frost last night and i think it will be fine down here but at some point i need to figure out how to SAFELY put it to bed for the winter.

I don't mean to totally hijack this thread but I would really like to see this thread provide others with useful information on the same questions i have.

I'm borderline between USDA 5b-6a. I overwinter my figs and about 150 other trees on the garage floor or on tables w/o additional protection. If I was the sort that was prone to forgetting and leaving the garage door wide open during REALLY cold weather (Al

Al -
I was still thinking to burry and mulch them, but husband thinks we can avoid that - and store them in basement.
So how do I know the tree is dormant?
Thanks

In the life of a fig tree, the true dormant period is a mere blink - it lasts about a week or so after the leaves fall.

Trees are pushed toward dormancy by decreasing day length. Technically, it's the increasing dark period that is the stimulus, but why quibble. ;o) Chill usually initially deepens dormancy, but continued chill is also the release mechanism. A certain period of chill is required to release trees from dormancy. Once the tree passes from the dormant stage, it is said to be quiescent, or quiet. It is prevented from growing by soil temperatures; although, it is capable of being stimulated to growth at any time, by soil temperatures above 42-45* for more than a day or two.

From this, you can see that trees in basements above 45* are going to grow. W/o adequate light, the growth will be weak and distorted, but more importantly, it will be a considerable drain on the plant's energy reserves. Most of the foliage will likely die (for various reasons), so these plants will enter spring with foliage in (often) bad shape and little or nothing in the way of energy reserves to push a new flush of growth.

Had the tree been kept cool and quiescent, it would have entered spring with batteries fully charged and raring to go. Those that think that because their trees survived an indoor winter stint they have a leg up on other trees because of the 'longer growth period' are usually mistaken. Your trees will perform better and gain more mass if they are kept cool and quiet well into spring. Even the trees I over-winter in my unheated garage leaf out at least a month earlier than I would prefer, but with 200+ containerized trees, a pit for over-wintering isn't an option.

Al

well, Can I just keep them burried where they spent entire spring and summer - east facing side of the house - and cover them with a box?

You can if you think the soil temperature will be warm enough that roots won't die - like against the foundation of a heated building - you prolly don't even NEED a box with that scenario. We've come full circle now, back to my original suggestion. ;o)

Al

can I stick a garden termometer in the pot so it measures soil temp at the roots and if it drops below 40 - I will pull them out? Otherwise, I would just pile leaves all around it and leave it where it is

Al, thanks for all your info and experience. I never would have realized that the garage floor would be a relative source of heat. so it is possible that i could cover the tree with a large card board box and place it on the wall next to the house. Its also interesting that the actual dormant period is so short. If i can get the tree to go dormant for the required week or so which shouldn't be to difficult then it is just a matter of keeping it in the quiescent period until spring which is the difficult part.

I'm now wondering if it would be best to not let the tree go dormant until much later in the winter and then take advantage of the warmer spring weather to let it wake up more naturally? Otherwise i can see if we had a sudden warm spell come late feb. for example it may want to wake up. I believe you said it needs a day or 2 above 45 and it may start to wake up and begin growing, so my question then is if the temps drop back down during the night is that enough to keep it from trying to wake up to early? Does the nighttime low temp need to stay above the 45 degrees or is it just the day time temp?

nathan

I'm not sure how you'd go about controlling the trees natural progression toward dormancy, but the garage floor also serves to cool the soil during warm periods. Ambient temperatures have little affect on stimulating the tree to growth beyond their affect on soil temperature, which is key in the onset of growth after quiescence.

Generally speaking, working hand in hand with Mother Nature, trying to replicate the environment she has provided the trees where they are naturally found as best you can, is going to give you the healthiest trees and best growth with the least effort/trouble.

Al