Overwintering Potted Trees

I would really like to have some input on this topic. I just can’t find any satisfying answers. I have quite a few grafted an ungrafted potted fruit trees… mainly jujube, persimmon, pawpaw, apple, pear. Can anyone point me to some actual data or information regarding root damage or mortality for different species in freezing temperatures? I keep seeing people say that the roots should be 2 zones less hardy than what the shoots can handle. Is this true? Stark Brothers seems to imply that 20F and below is where damage occurs,

“The problem is this: when the temperature dips to 20ºF and stays there for a while, it’s possible to freeze the core roots of the plants.”

I’ve seen other people saying 28F or below 28F. I accidentally left all my potted stuff uncovered for a night in the mid teens last year and everything was just fine come spring. Maybe some root damage but no mortality.

Please share with me some of your personal experience with this.

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You’ll never know unless you try for yourself. So many factors at play. Burying pots in the ground and covering them with something is your safe bet.

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Oh my gosh. I probably can’t find definite answers because nobody has them. Just a guessing game?

Basically. There are different areas of cells affected at different temps, and all the thresholds vary depending on species. If a tree incurred 15% root damage over winter but recovered the following season by regrowing new tissue, would the typical owner ever know this happened… nope.

Not much academic info out there, but I found this previously: Resistance of the roots of some fruit species to low temperature It seems to justify the 20ºF safety threshold for peaches.

The dominant factors are duration of critical temperatures and the size of the pot.

Moist soil will be slower to freeze than dry soil.

Are your pots already at the maximum size you can handle?
Can you array the pots next to each other or are the plants too large for this?

In Texas last winter we had some zone pushing weather. Of course it never lasts very long but I had some plants in pots that were out without protection…largest pot was 5 gallons and most were 2 gal or smaller. Lowest temps were 8-9 degrees. Trees were young jujube and Russian mulberry.

Katy


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I will tell you about my personal experience (Apple, Peach, Plum, Juju, Pear, Persimmons and Pawpaws). I graft and pot many trees a year, at the end of the year here in Ohio, I either plant them if i have a space for them or I put my pots in the ground. 10 years ago I tried a couple of years to just leave them in the pots above ground in a corner under an overhang with straw/hay around them, also would water them occasionally. Temps here can remain under freezing for weeks on end and even go a couple of months below 32 and down to below 0. My loss rate was 75 percent or more.

I now put all my pots in the ground deeper or at least level with the current dirt level in the pot. I have not lost one potted tree since doing it this way. If I have several rootstocks that don’t take, I will un-pot them and bunch them up all together and bury together and in spring, graft and re-pot.

I can’t give you specific numbers as other have replied the same, your situation and location will vary even with the ow temps in your state, you could have a situation where you can leave them above ground in a windless location, with morning sun everyday almost a semi controlled climate environment. Here in Ohio… it is more like wind, haze, snow and gloom until late spring.

Just a note, my Jujubes don’t do well here… Still alive but slow growers.

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Thanks for replies everyone. I’m going to see how they fare unprotected in the low 20s.

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Had potted peach, apricot, mulberry, blueberry and apple outdoor last year in 10 and 15 gallon pots. I covered them with oak leaves a few inches over pot rims. Temperature went to 0F and they all survived.

I believe @warmwxrules stores potted plants in an unheated shed all winter in WI. I would suppose he sees significant periods of time where the temperature in the shed is in at least the low single digits.

Encouraging replies here. Thank you. I do plan on covering them with some heavy white plastic as soon as I get home… just out of state for the next week and a half and a little concerned.

took some trans plants and cuttings in early fall. left them outside. were covered by snow in late nov. but still lost most of them over winter. bigger plants may do better. these were all z3 hardy plants. I’m in z3b/4a. i had my z5 lavender in my unheated garage but wrapped roots in a thick blanket. i thought it died but then started growing again in mid june. got to -35f a couple times w/ temps mainly -20f during the days in jan.-feb.

i gave my son an apple tree,potted, for planting next spring,in Marquette,Michigan. He has an unheated shed,where it will be stored.

since those are all deciduous i would put them in a garage or shed that doesnt get too much below freezing if at all. Thats how i store my pomegranate and figs.

If one has to go to all that trouble to dig a trench, etc., wouldn’t it be easier to just grow them in the ground to start with?

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Yes that’s a good point. But not always possible.

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Depending on your situation and equipment it can be easier, take less time than other options. Especially if your plans don’t include keeping them after the second year of growth.

@Marknado check out this topic.

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Thanks for directing me hear Bob. Looks like the perfect thread for answering my question. I have an outdoor shed so I may end up just sticking the trees in there. Now that the temperature is in the 20s I threw some dead leaves on my pots just to provide a little protection. The figs are in my garage for the winter.

I have a Wonderful pomegranate in a pot. It’s in my basement which is somewhat dark and 72 degrees. It has lost all the leaves. I wonder if 72 is too warm for a dormant tree. Not sure how long it will stay dormant. I plan on not giving it too much water.
I can move it to a brighter area that stays around 69 degrees. Will it do better in the cooler area? Will it make any difference? I’d rather not move it to the cooler brighter area (it’s the living room and this would be an eyesore) unless it increases the plant’s chances of getting through the winter a lot.