Is Concrete Bad For Winter Storage?

ShadyStump

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Today's project is putting my outdoor trees to bed for the winter.
I'm in a very old house, and half of the floor space is additions built on over time, including punch-outs for a closet on one corner and the laundry room on another. I thought I'd squeeze My trees under one of those, but the closet doesn't have the vertical space, and I realized the drier vent under the laundry could be problematic.

So I'm putting them on the back porch, which faces south and has a roof over it and a light wall on one side so it's only ope to the south and east.
I'm stopped dead, though, trying to decide if I should just set the pots on the concrete against the house wall, and hope that's plenty enough of thermal battery, or if concrete will sap more heat than deliver, so set them on a pallet.
It needs to work because I stole the spot from my dog, and I'll feel bad about it if it was for nothing.

What are your folks' thoughts?
IMG_20211120_105732_202.jpg
That window is the bathroom, BTW. It gets opened for hot showers, but I figured that's allot better than the drier vent.
 

Dav4

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I would expect the concrete to be a good thermal sink do to it’s mass and density and would stay relatively warmer because it is in contact with the ground and your house. Using the pallet would subject the trees to the ambient air temperatures all around, so the roots would definitely get colder. I’m undecided whether a southern exposure is good or bad in your climate but you have the makings of a decent cold frame there in my opinion.
 

Deep Sea Diver

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Great minds think alike @Dav4 !

Well, concrete isn’t a particularly good insulator, but it isnt a particularly good heat conductor either. the concrete will absorb the sun though and release the energy slowly if you get a lot. If you are concerned you might be wise to toss a sheet of used plywood or better still, a layer of small bark underneath the pots first…. I wouldnt put a pallet there as the air space below the pots is not something helpful.

You do have two good sides and bottom of a decent quick made cold frame already on site though. It’s possible you could just use translucent polyethylene sheets, like they sell in the hardware store and staple it to the overhead and sides and use old 2x4s for the bottom foundation. You’ll likely be wanting to make some sort of post for the corner and a vent for the bathroom and vent/access for a ventilation.

One material I used for framing my cold frame was 3/4 pvc piping. Here’s an image of my slapped together operation. It’s drafty but does the job.
2C3E1723-2EB0-4A92-9B42-0D07E65BF0B5.jpeg
cheers
DSD sends
 

ShadyStump

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Thanks for your thoughts.
I guess I'm caught up in the relativity of it. Imagine snow falling. On bare dirt it accumulates slower and melts faster compared to the patch of concrete it surrounds. So my mind thinks concrete must inherently be a terrible insulator and thermal battery.

I was going to place each tree in a cardboard box and heal them in with mulch, leaves, newspaper, etc. for insulation.
South is good in winter here, but southwest gets burned. I have south but not west, so should be good.
Oh, look! I found a mame pot in the leaves!
IMG_20211120_120616_192.jpg
Because, ya know, that's my budget right now.
😭

I think I'll go with your guys' suggestions. I was just over thinking it.

Thanks again!
 

Lorax7

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You do not want an air gap under the pot. The advantage of setting pots on the ground for overwintering is that the earth has a high heat capacity, so it’s temperature is very stable, changing very slowly in response to changes in air temperature. So, definitely do not put them up on a pallet. That’s a recipe for dead trees. The main question to consider regarding your porch is whether the concrete is directly in contact with the ground with no crawl space or other air gap between.
 

ShadyStump

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You do not want an air gap under the pot. The advantage of setting pots on the ground for overwintering is that the earth has a high heat capacity, so it’s temperature is very stable, changing very slowly in response to changes in air temperature. So, definitely do not put them up on a pallet. That’s a recipe for dead trees. The main question to consider regarding your porch is whether the concrete is directly in contact with the ground with no crawl space or other air gap between.
It is. It's just shaded much of the day because of the semi-enclosure, so doesn't warm up much, especially that back corner.

Just got going on the whole project. Laid some wood slabs from a broken section of fence down in that corner, filled any gaps with leaves and mulch, slid the pots that would fit into boxes and mulched them in the boxes.
My think is the wood shouldn't disrupt heat transfer too much- between the concrete and the house it should stay warm, and will help with drainage when I need to water. I'd hate to get through winter and find rot everywhere.
 

Treefer

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I have a glassed in porch with a carpeted concrete floor. I have been told by bonsai elders that concrete will suck the moisture out of the pots. So, to be safe, I place Styrofoam sheets on the carpet and cover that with a blue tarp to protect the carpet when watering. Deciduous against house wall with furniture blocking most light. Conifers go against outside wall.
 

Deep Sea Diver

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Concrete does absorb moisture mainly from the air in an enclosed space,… yet it also gives off moisture when the humidity it’s low until an equilibrium is achieved… however fleeting.

That said, I’m not seeing the concrete sucking the water out of your pots as being something to be concerned about.

The bonsai media isn’t in direct contact with the concrete as your pots should have bottoms and legs….. and you are checking moisture levels and watering as needed….?So there ought to be no worries about a ‘concrete sucking moisture phenomena’.

Your carpet is a whole ‘nother story. Moisture protection is a must there… unless you want mushrooms growing out of your carpet like we did when our roof slow leaked by our fireplace onto the carpet!

btw: Shouldn’t the conifers be outside? Or are your species at risk?

Cheers
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ShadyStump

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Concrete does absorb moisture mainly from the air in an enclosed space,… yet it also gives off moisture when the humidity it’s low until an equilibrium is achieved… however fleeting.

That said, I’m not seeing the concrete sucking the water out of your pots as being something to be concerned about.

The bonsai media isn’t in direct contact with the concrete as your pots should have bottoms and legs….. and you are checking moisture levels and watering as needed….?So there ought to be no worries about a ‘concrete sucking moisture phenomena’.

Your carpet is a whole ‘nother story. Moisture protection is a must there… unless you want mushrooms growing out of your carpet like we did when our roof slow leaked by our fireplace onto the carpet!

btw: Shouldn’t the conifers be outside? Or are your species at risk?

Cheers
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Mine are, or did you mean @Treefer?
 

ShadyStump

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BTW, the current state of things...
IMG_20211120_133605_995.jpg
The pallet is there waiting for me to make a dog house since I stole her spot.
The big brown basket in the center had to be raised considerably. It's a natural semi-cascade Gambel's oak, so need head(?) room.
Think I'll do some re-arranging, though, before the real cold sets in. Maybe a roll of plastic on payday. We'll see what the Christmas can gives.
 

sorce

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Soaked and Froze....
Soaked and Froze....
You know they stay bros when they're...
Soaked and Froze.

I wouldn't worry about rot.

I think you'll fare better on concrete over the ground, since mice can't burrow directly underneath, and the trip to get to them is arduous and hopefully remains unknown.

Though, I have so many mice in the yard, I can breed owls, I have never had damage from them leaving trees on the ground, so I still think an early fall connection to the myc network is more beneficial for winter safety than protecting from mice.

Sorce
 

Deep Sea Diver

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On concrete on bark would work fine would be my vote…. but in my experience one has to start at some point in their practical process before fine tuning.

You can always sic the dog on the pesky rodents! 😉

I’ve fine tuned the way I winter over my bonsai, especially the growing group of azaleas, pines and maples, every year.

It will be interesting to see what happens to your trees.

Cheers
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Eckhoffw

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I’d say warm earth is best but concrete should be good.
I put down foam board over the concrete.
I’d rather sleep on that.
 

Paradox

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My coldframe as I was constructing it.
It worked so well I expanded it twice to make it bigger
 

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leatherback

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The advantage of setting pots on the ground for overwintering is that the earth has a high heat capacity, so it’s temperature is very stable, changing very slowly in response to changes in air temperature.
This is what it is all about

But..
Laid some wood slabs from a broken section of fence down in that corner
This is what reduces that benefit. Wood is a great insulator

Styrofoam sheets on the carpet and cover that with a blue tarp to protect the carpet when watering.
This is like thinking you need to protect the pots from the cold down below. But you want it connected to the relatively warm earth!

I put down foam board over the concrete.
I’d rather sleep on that.
But you are a warm body, generating heat. So you do not want a thermal body connected. A cold object, such as a pot, will stay slightly warmer connected to earth than it would be when isolated from the earth.
 
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