Greenhouse for bonsai

[JoeR]

I used to overwinter Chinese elms in an unheated garage in Chicago, so they can take the cold. Just protect them from the wind and make sure the soil doesn't dry out (I used to put snowballs on my bonsai in the garage). And as far as an apple tree goes, apples are cold hardy trees that NEED a cold winter. There are some cultivars that "may" still fruit in warmer climates, but I have never had any luck with them even though they sell some in nurseries down here in Southern Cal.

How much warmer is your unheated garage compared to the temps outside? How does the unheated garage help if its the same temperature?

 

[Bonsai Nut]

It helps in a couple of ways...

First, it is NEVER as cold as the outside. Outside could be 20 and garage would be 30. Still below freezing, but not as brutal. But the big advantage is no wind... no exposure. Cold doesn't kill trees that are in full winter dormancy... dryness does. Cold and wind = freeze-dried dead tree. So keeping it in a cold frame, or unheated greenhouse, or unheated garage, protects the trees from drying out. They hunker down, rest, and wait for spring. I would make snowballs, and put them on the soil of each of my trees in the garage. As long as the temps were below freezing, the snowball would stay. As soon as it got a little warm, the snowball would melt into the soil and let me know it was time for another snowball

 

[JoeR]

It helps in a couple of ways...

First, it is NEVER as cold as the outside. Outside could be 20 and garage would be 30. Still below freezing, but not as brutal. But the big advantage is no wind... no exposure. Cold doesn't kill trees that are in full winter dormancy... dryness does. Cold and wind = freeze-dried dead tree. So keeping it in a cold frame, or unheated greenhouse, or unheated garage, protects the trees from drying out. They hunker down, rest, and wait for spring. I would make snowballs, and put them on the soil of each of my trees in the garage. As long as the temps were below freezing, the snowball would stay. As soon as it got a little warm, the snowball would melt into the soil and let me know it was time for another snowball

Thanks,

I was curious because I always hear about people using their unheated garage but it never made sense to me. I have a shed in my yard that is pretty much the same temperature inside as outside and I wondered how that could possibly help.

 

[BrianBay9]

Tieball mentioned going underground.That is what I do.Make sure to use a gravel bottom so the earth heat can radiate up through.Also put on non flood,at top of land and also in the shade.Mine is almost 3 feet deep and it never falls below 27F when it is single digits at night.There is usually some dew on the bottoms of my pots no matter what the temperature is.
Can also run a fluorescent low intensity light for added warmth I have been told.
In the autumn you can shoot a garden hose in it and flood it a couple days before you put away the trees and the humidity from the mud after it drains deep under the gravel keeps trees moist all winter.
The serious enthusiast could actually do something on a larger scale too.Believe I saw it in Bonsai Focus.It was like a walk in shed with no floor.Just a deep cold frame that you walk down into.Same principle I use with the mud and everything.That is where I got the mud idea.

Saw a guy once who used an in-ground swimming pool. He put on a poly cover, and installed a door at the steps

 

[JudyB]

Saw a guy once who used an in-ground swimming pool. He put on a poly cover, and installed a door at the steps

smart guy...

 

[edwin norden]

Is some cold frame will to the work for the winter ?
Something like this

We have -5 -10 usual and some extreme -20 -25.
Will my trees survive in this mini cold frame or i should put some heat in there as well?

Next winter i want to put some trees to cold frame and i hope something like this will be ok.

 

[petegreg]

I think this will work for cold hardy species. They will be protected from temperature extremes and drying winds. But do not let the sun look directly through the glass and temperature rise too high.

 

[edwin norden]

Then i should built to shade to protekt from sunlight?

 

[petegreg]

Yes, you can place the cold frame in the shaded area or turn the window orientation to the north.
BTW, the lowest temps you have stated are similar to those here. I usually over winter my cold hardy trees buried in the garden. In order to separate and protect the pots and substrates from surrounding field soil I cover the pots by agrotextile. (This winter I have left the most of trees on my balcony, buried only shohin sized ones and e.g. japanese maples and mulberries in the garden, was able and ready to protect the trees on balcony more, built some polyshelves, but this is not a winter...)

 

[JoeR]

You definitely need a heat source. I know for my cold frame setup, I have to use a heat element just to keep it from freezing at night; If I do not turn the heat on, it only stays like a max of 5 degrees warmer than outside.

But I have delicate plants in there currently.

 

[armetisius]

Be certain to check out biological heating/bale gardening.
My bales produced a steady 140F all last winter. Costs?
Bale of straw + nitrate fertilizer to kick start the bacteria.
Extreme old school method of heating.

 

[JudyB]

This cold frame will work for you depending on what trees you are protecting. If the trees are hardy to your area, then this will work with some thought to placement, like out of the sun, or with shade cloth. You'll want to make sure you have an auto opener on the lid, so the plants won't get too hot when it warms up in the day.

 

[whfarro]

Be careful not to "bake" trees in a cold frame. Direct sunlight through that glass/plastic top can really generate and trap some serious heat. Make sure you place it with the proper orientation to avoid that.

 

[Bonsai Nut]

Trees in dormancy don't need sun. In fact, it can actually cause problems related to heat and dryness. When I would overwinter my trees in an unheated garage, I certainly didn't leave the lights on

 

[MauroUna]

You definitely need a heat source. I know for my cold frame setup, I have to use a heat element just to keep it from freezing at night; If I do not turn the heat on, it only stays like a max of 5 degrees warmer than outside.

But I have delicate plants in there currently.

What kind of trees? Freezing is not necessarily a bad thing

 

[JoeR]

What kind of trees? Freezing is not necessarily a bad thing

They are fully leafed out, semi-rooted cuttings. Root divisions, actually