Chinese elm Wintering

rhawes

Mame
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I have a few chinese elm and was thinking of leaving outside until december when in Janurary the average lows are in the 20s and highs in the 40s. I would place them in a greenhouse. I have read to bring them inside when bellow 40 degrees F. I am quite confused about how to care for these trees. I am in Lancaster, Pa.
 

Cofga

Omono
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I am in zone 6b/7a and I just leave mine outside all winter under a blanket of leaves.
 

caffeinated

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My many Chinese elms stay outside all winter, through a week or two into the twenties or teens occasionally, sometimes buried in snow. They're hardy trees. They've dropped all their leaves and are dormant at the time so not a big deal. They can live without a dormancy period, so you can bring them inside for the winter, but ( conjecture) I think they do better having gone through and coming out of dormancy.
 

leatherback

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Mine stay outside. Last winter we had a good long cold spell (5-15F range for over a week) and they only got shelter then, unheated open-ventilated shed.
 

Paradox

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I put mine in a coldframe on the north side of my house. It usually goes in one of the window wells. It drops below 40 out there.
 

PA_Penjing

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important to note that many of the cultivars are not nearly as hardy as the straight species. That being said I don't like any of the cultivars so I only have experience with regular old Chinese elm. In the past I have left mine out all winter in a small pot without a problem. I won't be doing this anymore, because I think protecting roots during summer heat and winter extremes gives far more vigorous growth come spring. Every person here will have a different opinion but after a lot of research I personally try not to let the roots get below 20F, they won't die until below 14F but that gives me a buffer. Important to note that air temperature does not equal soil temperature. And soil temperature does not equal root temperature. The plant is full of anti freeze. On a 17F night the soil could be something like 20F (in a fairly small pot, warmer in a larger one). And the roots? well I have no idea because I have no way to measure, but knowing they are almost definitely above soil temperature puts them in a safe range. I begin moving trees into shelter around 19F just to be safe. But all this is assuming they are in a decent open soil. If your tree is a tub of wet mud I would be far more protective. As the soil freezes solid into block it will mechanically destroy roots that will later root in the cold muddy pot. But to answer your question... 40F is way more protection than CE need, in fact if you keep them above that temperature I don't think they would even go fully dormant.
 

PA_Penjing

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Also 20 degrees and 14 degrees are not random numbers I chose. There are well documented biological changes that take place at that point, here is a popular reference. I like this article because it's for bonsai folks and not the nursery trade in general. https://www.evergreengardenworks.com/overwint.htm

Also while linking this I just realized it's 14 that kills, so 15 is the number not to fall below. Regardless..... if you take action around 19/20 degrees you're still being overly safe according to this article
 

PA_Penjing

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Not sure why you think this? Trees do not have an internal heater.
I guess I misremembered that portion. I just read up on tree's anti-freeze system and I guess just because they don't freeze doesn't mean they are warmer than the soil. Good catch. I guess it has been a long time since I read up on any of this stuff. But the bottom line remains the same. 19 degrees F is a safe temp for most hardy trees, or -7C for you guys.
 

Maiden69

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important to note that many of the cultivars are not nearly as hardy as the straight species.
I like this article because it's for bonsai folks and not the nursery trade in general. https://www.evergreengardenworks.com/overwint.htm
My seiju stay outside year long. This year it was buried in snow for almost 2 weeks and didn't skip a beat in spring.

Funny you linked Brent, I talked to him about wintering my trees and he recommended leaving them outside on the floor with the pots covered with mulch. I did this even with the trees in pond baskets and not one had an issue.
 

karen82

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From what I've read on Chinese elms (and my own very limited experience), either option would be good. They don't seem to have a strict dormancy requirement like many trees do.
I have two tiny-leafed Chinese elms (unknown cultivar, but the both are the same), I planted one in the ground, and the other one I leave outdoors til it gets just about as cold as you are planning - mid-December in my case - and then bring it in and keep it in a cold greenhouse. Both seem to be doing quite well. I think that if they were both in pots, the greenhouse one would be doing better. The one in ground does grow a little more vigorously once it finally gets going in June but I think that is only because it's in the ground. I've done this for 2 winters now and they have responded the same both times.
 

PA_Penjing

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My seiju stay outside year long. This year it was buried in snow for almost 2 weeks and didn't skip a beat in spring.

Funny you linked Brent, I talked to him about wintering my trees and he recommended leaving them outside on the floor with the pots covered with mulch. I did this even with the trees in pond baskets and not one had an issue.
Yeah zone 8 is warm enough that I would leave my trees out all year, even on the bench for all but the coldest nights.

And @Davidlpf I'm impressed if those temps are in Fahrenheit, but I suspect that's celsius. In which case you are well within all the limits for those elms as far as i am aware
 

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