What is the perfect temp for a wintering storage shelter?

[aml1014]

No. It does NOT really depend on the size of container. It's not that simple. It mostly depends on what's IN the container.

The soil in a 6 inch pot can freeze solid with no problems, just as the soil in a 24" pot can too. It all depends on the species in the pot's ability to withstand Intracellular freezes. Those kinds of low temperature come with extreme, constant lows below 15 degrees or so (this is tremendously variable). Smaller pots can reach those lows more quickly because they have smaller mass, but those same temperatures can affect larger containers as well.

A Ponderosa pine in a solidly frozen six inch pot at 0 F will be fine for days, while a Japanese maple at that temp in a 12" container will get winter kill or lose branching...

I absolutaly agree that larger containers will freeze same as smaller pots AT constant low temperatures, that's nearly impossible in our climate as it can be 14° at 7am and 60° be 11am so those larger containers never freeze through until our rough month which is February and March can be hot, or very cold. It's very unpredictable. Nevertheless, larger containers do take longer to freeze then smaller containers do, that's a fact. Many places in the country can stay under 32° for weeks at a time, but we do not have that here even if the trees are kept in full shade.

Aaron

 

[coh]

You've got to know your environment. Remember what happened to M.Frary's trees last winter. Leaving them outside under mulch and snow is certainly the easiest approach, but if you have a significant critter problem (like I do), it's a huge risk. Similarly, indoors in barns or garages can be a risk for the reasons rockm gave. I've had major damage (mainly from voles and mice) with trees wintered outdoors on the ground, and in my barn on the floor. It wasn't until I built the enclosed shelter inside the barn, and got the trees up on tables, that I eliminated the critter problem. Even with the trees up off the floor, though, I do put out traps and check the shelter periodically to make sure no critters have found their way inside.

 

[rockm]

I live in the same Zone 7 as you. I'm familiar with the temperature swings in the winter and which pots freeze through and which can take longer--and ALL of my trees are frozen solidly in their pots come February and stay frozen even as the air temperatures warm into March. I want it that way.

Which is why mulch is so much better than an enclosed, heated, insulated structure. Mulch lags cold AND warm temperatures. Using it, you're basically using mass to protect the roots, which is mostly the same thing as planting them out in the ground. The temperatures are slow to rise in the spring and slower to drop in the winter, but remain mostly even on the low side in the winter. Constantly hovering around the 35 -40 degree mark is dangerous, as either the trees don't reach steady dormancy, or are too quick to rouse themselves in the spring.

Do this for a few years and you will understand why that's important.

 

[aml1014]

Do this for a few years and you will understand why that's important.

I've been doing it for a few, I have the knowledge of decades at my disposal, and I've been in the nursery business for a but now. All have taught me everything I need to know about wintering trees, I do use mulch for some, others go in the structure, and some stay out exposed to it all. I've never lost a tree to the cold, or waking up too early so I must be doing good lol

Aaron

 

[rockm]

Um, you seem to have changed your plans significantly? The first post said you were going to put them all in the structure, or did I misread?

 

[aml1014]

Um, you seem to have changed your plans significantly? The first post said you were going to put them all in the structure, or did I misread?

I never specified everything goes in. I rather said "them", them being more tender species, and trees in very shallow containers. Most of my trees in training get mulched in next to my structure, and the hardy trees like my ponderosa pines and fir just sit on the bench unmoved all year. There's no way all my trees would fit in my coldframe.

Aaron

 

[Bonsai Nut]

There's another misinformation. With the exception of some deciduous/sensitive trees, freezing the roots is not a bad thing.

I would overwinter my trees on shelves in an unheated garage in Chicago. The temps were about 10 degrees above ambient temperature outside. They would freeze as solid as a block of ice once it got cold enough. The only issue I had was with the soil drying out, so I would put a snowball or a few ice cubes on the soil. Over the winter the snowball or ice would slowly dwindle, and I would replace as necessary.

 

[coh]

I would overwinter my trees on shelves in an unheated garage in Chicago. The temps were about 10 degrees above ambient temperature outside. They would freeze as solid as a block of ice once it got cold enough. The only issue I had was with the soil drying out, so I would put a snowball or a few ice cubes on the soil. Over the winter the snowball or ice would slowly dwindle, and I would replace as necessary.

Did you have species with roots that are supposedly sensitive to lower temps, such as tridents? If so, no problems with them? I know Chicago can get some pretty cold periods so I would think you sometimes had temps in the garage down into the single digits...if not briefly lower.

 

[rockm]

I never specified everything goes in. I rather said "them", them being more tender species, and trees in very shallow containers. Most of my trees in training get mulched in next to my structure, and the hardy trees like my ponderosa pines and fir just sit on the bench unmoved all year. There's no way all my trees would fit in my coldframe.

Aaron

That's not what you said initially.

"I'm sure most everyone here knows what tree's I have because I've posted several pics but here is a list of the tree's that will be in there anyway

4 Japanese Maples
2 Elms
1 Hackberry
1 Ume/Plum
2 Junipers
1 JBP
1 Boxwood
1 Ponderosa

JBP, Junipers, and Ponderosa won't go in there until temps drop into the teens."

 

[aml1014]

That's not what you said initially.

"I'm sure most everyone here knows what tree's I have because I've posted several pics but here is a list of the tree's that will be in there anyway

4 Japanese Maples
2 Elms
1 Hackberry
1 Ume/Plum
2 Junipers
1 JBP
1 Boxwood
1 Ponderosa

JBP, Junipers, and Ponderosa won't go in there until temps drop into the teens."

Those are abqjoes trees, I have a larger variety of species but I do have most on that list.

Aaron

 

[Vance Wood]

Mine is a Trident root over rock Shohin. So what you're saying is that I'd be better off pulling it from the pot and transferring it over to a larger container and pack it in Pine Bark?

bury the pot rock and all up to the level of the base of the trunk in a box full of PBM, or some other non toxic substrate.

 

[rockm]

Those are abqjoes trees, I have a larger variety of species but I do have most on that list.

Aaron

Sorry then. I got lost in the New Mexicans.

 

[aml1014]

Sorry then. I got lost in the New Mexicans.

Lol that's cool, I kinda figured but wasn't sure.
I do think the pondy needs to be left out though, it can handle anything winter throws it's way. The others I'd either mulch in the shade or do as he is and build a structure and aim for anywhere between 25-40°. My structure has gotten down to about 18° with no damage to anything.

Aaron

 

[rockm]

Like I said, structures that try to hold that narrow 25-40 degree margin aren't necessary for most species in Zone 7. We don't get cold enough for long enough to warrant that king of thing. I know people here who have tried various kinds of enclosures, from unheated garages to plywood shelters with heaters. Most of them have given up on those things, or have learned how to manage them with ventilation--heat gain in any structure is inevitable.

I overwinter all of my trees in mulched beds sheltered from the sun and wind in the back yard. Thick cover (8-12 inches) of hardwood mulch. No cover other than a wind break. I store tridents and Japanese maples in two foot deep cold pit that has a board lean-to roof that is open all winter. The roof is angled to keep the sun and excess rain out. The trees in it are also under a foot of mulch. I've had southern species survive sub-zero temps several times over the years. The deep single digit or below cold rarely lasts for more than a week.

Trees under mulch never require water over the winter, IF you make sure the mulch is wet all the way though when you apply it. Rain, snow and ice provide all the water that's needed.

 

[Bonsai Nut]

I would overwinter my trees on shelves in an unheated garage in Chicago. The temps were about 10 degrees above ambient temperature outside. They would freeze as solid as a block of ice once it got cold enough. The only issue I had was with the soil drying out, so I would put a snowball or a few ice cubes on the soil. Over the winter the snowball or ice would slowly dwindle, and I would replace as necessary.

Sadly, it has been 20 years since I did this, so I don't remember if I had tridents or not (I think not). I know for a fact I had Japanese Maples, Japanese Black and White Pine, lots of junipers, some boxwoods... and some other stuff Sorry I can't be more specific based on memory.

 

[Cadillactaste]

You also need to focus on those warm days...which surprisingly...surprise us. A way to vent to let the heat out which has built up.