Need guidance - dormancy indoors (several species)

[Aphystic]

A little bump here.

I just want to ask: my Chinese elm that I am planning on keeping outdoors this winter in a “box” of mulch - right now it’s still in a normal potting soil and not a more coarse bonsai mix - is it still ok or will it freeze as a huge block of ice and kill the roots? I heard I shouldn’t repot before next spring but I’m afraid it’ll die in its current soil.

 

[Shibui]

I do not have to deal with such cold but if trees in the ground can cope with frozen roots I cannot see why trees in pots can't cope with frozen roots too? Soil type should have relatively little bearing on how roots cope with cold. Same temps in a pot with soil as in a pot with pumice or any other substrate?

 

[Orion_metalhead]

The zelkova just leave outside, not dug in, but pile the mulch around the pot... im same usda zone here in NJ and my zelkova do just fine outside with the pot mulched.

 

[Bonsai Nut]

I agree with everything @rockm has said in this thread - including the identification of your Chinese elm as a Ulmus parvifolia (not a Zelkova or Zelkova serrata)

I'll just add my own experience. Since moving from Southern California to North Carolina, I have had to start overwintering trees that I could keep outdoors all year in SoCal. Not only ficus, but Brazilian rain trees, Brazilian ironwoods, Texas ebony, ficus, fukien tea, and probably some I am forgetting. I have kept them in two different houses in east facing windows (bright, but indirect sunlight) and have had no problems. It is important to note that tropicals often have their own dormant seasons in the wild - but they are usually brought on by a dry season. When you bring your trees indoors, expect them to slow down significantly, and watch that you do not overwater. Do not try to force the same growth that you would see outdoors in the summer with direct sun and rain.

 

[rockm]

I do not have to deal with such cold but if trees in the ground can cope with frozen roots I cannot see why trees in pots can't cope with frozen roots too? Soil type should have relatively little bearing on how roots cope with cold. Same temps in a pot with soil as in a pot with pumice or any other substrate?

But soil does have a bearing. Heavy dense soil that doesn't drain keeps roots to wet in zone 7 winters, where we don't have a steady below freezing climate. Temperatures in the winter give us snow (which is great for overwintering bonsai) and rain (which is more common and keeps bonsai soggy during inactive periods) That constant wet and freeze/thaw cycle can kill roots that are constantly wet--for many of the same reasons constantly soggy soil in the summer does--no drainage promotes rot which can take hold more quickly when roots are inactive and unable to grow.

Additionally, roots freezing happens in more than one way. Yes, trees in the wild can handle (mostly, until they can't) for the most part frozen roots aren't much to get concerned about, UNLESS you get dramatically deep freezing that is early and/or lasts for more than a week or so. Intracellular freezing, in which water inside plant cells freezes--kills plants. It happens when temps are mostly consistently below 25 or lower for a week or more (mulch helps lag these temps in garden beds staving off the worst --hopefully).

Free draining soil is a lot better than a soil that freezes into a solid lump.

 

[Aphystic]

But soil does have a bearing. Heavy dense soil that doesn't drain keeps roots to wet in zone 7 winters, where we don't have a steady below freezing climate. Temperatures in the winter give us snow (which is great for overwintering bonsai) and rain (which is more common and keeps bonsai soggy during inactive periods) That constant wet and freeze/thaw cycle can kill roots that are constantly wet--for many of the same reasons constantly soggy soil in the summer does--no drainage promotes rot which can take hold more quickly when roots are inactive and unable to grow.

Additionally, roots freezing happens in more than one way. Yes, trees in the wild can handle (mostly, until they can't) for the most part frozen roots aren't much to get concerned about, UNLESS you get dramatically deep freezing that is early and/or lasts for more than a week or so. Intracellular freezing, in which water inside plant cells freezes--kills plants. It happens when temps are mostly consistently below 25 or lower for a week or more (mulch helps lag these temps in garden beds staving off the worst --hopefully).

Free draining soil is a lot better than a soil that freezes into a solid lump.

So is it appropriate to repot my Chinese elm now before the winter? I’m not sure what I should do, all I’ve heard is that repotting should be done in spring.

 

[rockm]

So is it appropriate to repot my Chinese elm now before the winter? I’m not sure what I should do, all I’ve heard is that repotting should be done in spring.

No, not really. You're going to have to get the tree through the winter as is. You could do a fall repotting, many people do it. But if you're asking the question, you might not have the know how to do it correctly. Incorrect, or overzealous root work in the fall can complicate overwintering.

 

[Aphystic]

No, not really. You're going to have to get the tree through the winter as is. You could do a fall repotting, many people do it. But if you're asking the question, you might not have the know how to do it correctly. Incorrect, or overzealous root work in the fall can complicate overwintering.

Am I better off keeping it in the current soil and watering sparsely?

I’d like to repot it now if possible.

 

[Orion_metalhead]

Id leave it as is and repot in spring. Surround the pot with mulch. Under neath, provide clear drainage, either some stone or gravel, maybe extra mulch. You just want the pot to drain excess moisture when it thaws. If youre going to get some reaaaallly cold weather, provide a wind-break by covering with a tarp (watch for potential snow load/branch breakong). If its going to snow, leave uncovered. If youre getting a little rain, leave uncovered. If youre getting more than a few hours of drenching rain, cover. I havent lost a chinese elm with these tactics. Im USDA 7b in NJ. I have my elms in free draining bonsai soil. I would be more attentive to soil moisture in your situation, due to the more water retentive potting soil.

 

[Shibui]

But soil does have a bearing. Heavy dense soil that doesn't drain keeps roots to wet in zone 7 winters, where we don't have a steady below freezing climate. Temperatures in the winter give us snow (which is great for overwintering bonsai) and rain (which is more common and keeps bonsai soggy during inactive periods) That constant wet and freeze/thaw cycle can kill roots that are constantly wet--for many of the same reasons constantly soggy soil in the summer does--no drainage promotes rot which can take hold more quickly when roots are inactive and unable to grow.

Point was more about freezing wet soil V aerated soil - that both types will get to the same temps so no difference in freezing stakes.
I take the point that soggy soil with temps above freezing is definitely an issue. We have that here too through winter when it is wet and cool but not frozen.
It may be a little late in the season for Fall repotting so I suspect that best action for @Aphystic would be to manage soil moisture through winter by trying to limit how much water gets into that soggy soil.

UNLESS you get dramatically deep freezing that is early and/or lasts for more than a week or so. Intracellular freezing, in which water inside plant cells freezes--kills plants. It happens when temps are mostly consistently below 25 or lower for a week or more (mulch helps lag these temps in garden beds staving off the worst --hopefully).

This freezing should not be better or worse with different soil types. Intra cellular freezing is intracellular freezing whether it is wet or dry. I guess each species has its own minimum temps which is what the plant hardiness zones is all about. Knowing what species can cope with what temps informs winter actions. - indoors, mulch, fully in the open, etc.
I guess mulching pots is good insurance even if the species is hardy?

 

[Aphystic]

Point was more about freezing wet soil V aerated soil - that both types will get to the same temps so no difference in freezing stakes.
I take the point that soggy soil with temps above freezing is definitely an issue. We have that here too through winter when it is wet and cool but not frozen.
It may be a little late in the season for Fall repotting so I suspect that best action for @Aphystic would be to manage soil moisture through winter by trying to limit how much water gets into that soggy soil.


This freezing should not be better or worse with different soil types. Intra cellular freezing is intracellular freezing whether it is wet or dry. I guess each species has its own minimum temps which is what the plant hardiness zones is all about. Knowing what species can cope with what temps informs winter actions. - indoors, mulch, fully in the open, etc.
I guess mulching pots is good insurance even if the species is hardy?

I will bury it in mulch, was thinking a big plastic box with holes and filled with mulch.

However, should I try to keep my organic soilt that my Chinese elm is sitting in just slightly moist the entire winter?

My big Japanese maple don’t get any water between having lost its leaves until buds are showing and it’s doing great but it’s also in a bigger pot, much bigger

 

[Shibui]

However, should I try to keep my organic soilt that my Chinese elm is sitting in just slightly moist the entire winter?

That would be my preference. If I thought I could keep it just damp through winter I would avoid repotting now.
If there's no way to manage moisture through winter I would probably opt for emergency out of season repot now, knowing that not repotting is likely a death sentence and that Chinese elm are tough and have survived repotting at all times of the year.
Final decision must be yours as we don't have the full picture of your conditions, resources, etc that may influence the decision.

 

[Aphystic]

That would be my preference. If I thought I could keep it just damp through winter I would avoid repotting now.
If there's no way to manage moisture through winter I would probably opt for emergency out of season repot now, knowing that not repotting is likely a death sentence and that Chinese elm are tough and have survived repotting at all times of the year.
Final decision must be yours as we don't have the full picture of your conditions, resources, etc that may influence the decision.

I will be able to manage moisture because it’s under a roof and protected from rain/snow but it will freeze so as long as that is not an issue in its current soil, I think it’s better to keep it as it is until spring