Wintering Bonsai in Minnesota

Hello. I was wondering what to do with bonsai during winter. I have heard suggestions such as insulating them, burying them in the ground, cold frames, refrigerators, etc... But in Minnesota the temperature gets to 20-30 F below zero and the frost line is about 3 feet below the surface. Oh and we often times don't get much sun for days and days (so I doubt a cold frame would be much help). Any suggestions you can ofter would be greatly appreciated. Thank you very much.
~Michael

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Jay

Mike, Good to plan early! I am a novice living in zone 5b/6a area. We get cold but not like you. First the lack of light you mention as a possible problem....is not a problem! When the trees are dorment they do not require much light! I winter my trees in an unheated garage and place them near a north faceing window. The garage moderates the temperature. If you have a garage that is unheated but shares a wall with your home it may get enough heat from the fondation to moderate your super cold temps. If you are growing native trees, they survive in the ground in nature so with a little help they can survive as Bonsai. What zone are you in?

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A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing

Well, I am in zone 4a/b so temps generally get around -20 to -30 for the cold days (which actually in the past several years has only been for a few weeks at most). I do have an unheated garage connected to the house, but the problem is the temp still gets below zero (generally not below -10) and I'm told 15 degrees is mandatory to prevent roots from freezing. I need to find some way to insulate the pot base. So far the only solution I've come across that I think would work is to dig a trench (3 - 3 1/2 feet!) and keep them in there for winter. I wish there were a better idea though...
~Michael

Jay

Mike.....I did not mention this added feature of my in garage set up, a heater. Now let me give you the disclaimers: - I am a novice. My trees used this last winter only for the 3-4 really cold days. I have a remote probe thermometer in with the trees to tell me the temp. But here goes.

My trees are on a shelf by the north window. The shelf has 3 inch high sides. The trees are packed (loosely) with peat moss or strofoam. I have a heater under the shelf.

The heater is simply some 1/2 inch copper tubeing running under the shelf up one side and back down the other with cross pieces every 12-18 inches. The tube is turned up at the ends by 8-10 inches. I fill the tube with car antifreeze. I place under the copper tube some heat tape with a thermostat. It comes in various lengths I started small covering approx 1/2 the tube. The thermostat does not come on until the temp is below 35 degrees F. and will not heat the pipe to more than 45 degrees. Now these temps are too warm. But remember the pipe is below the shelf and the trees are insulated from the shelf as well. This method by the thermometer I use never got warmer than 38 degrees. In addition, I did not even plug it in until the temps were reading in the garage below 30 degrees and likely to remain cold. I think if you were to use something like this and adjust the amount of heat tape or percentage coverage of pipe you could still use the garage! Now remember I am a novice who just used this for the past (mild) winter.

Does anyone else see any downfalls in this method if properly adjusted

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A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing

shane1130

I live in Northern Minnesota, Duluth, The zone here is 3 or 4, I think I am 4 as I am close to Lake Superior.
What has worked for me to winter my bonsai.
All of my outside trees are species zone hardy to the area.
I bury the pots so the ground is level with the surface if the pot, put a couple of inches of mulch over the surface of the roots. As soon as it snows I cover the trees with snow, to protect the foliage. I don't mulch the foliage as the one year I tried it I got snow mold.
The snow covering insulates the trees and keeps them between 25 and 32 degrees, it is the below zero cold that kills stuff. Think about it, a hardy tree out in the wild freezes and still lives. The key is using zone hardy stock.

Shane

Earl

We don't have quite that cold but 0 is sure common. I just mentioned in another post that I have a friend who takes those grow mats (I think I said heat tape in the other post...hope he reads this) that nurseries use for seedlings and sets his pots directly on top of them. He has them hooked up to a low temp thermostat and sets it for 32 degrees. He has beautiful, wonderful trees so it works. It would be a very easy solution in your garage. The foliage doesn't have to stay warm, only the roots.

The reason a pot can freeze and kill the same plant that won't die in the ground is because the roots are so constricted they can freeze hard and stop all water, air and food intake where in the ground they usually will extend down below the frost level.

Jay

Earl, sounds like your heat tape/mat is a similar direction to my pipe below the shelf with heat tape (mentioned in post above). It is a good system. You do have to be careful not to warm the trees to much. Different trees react differently to warming temps but I have been told to try and maintain a max of high 30's F to maintain dormancy, slightly colder is even better for most trees.

__________________
A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing

Thank you all for the suggestions. I guess I'll just have to pick one and try it. It was especially nice to hear from someone in my area that has hands on experience with this cold weather.
Shane1130, when you say the key is using cold hardy stock, do you mean plants that have been grown in the area from the beginning; or just plants that have been hardened by the frosts of fall? It's difficult to find plants in nurseries that haven't been shipped from a different area.
Jay and Earl, do either of you have an idea on roughly how expensive the growing pads are (in terms of the heating bill)? I expect not too much but when you have consistently cold weather...

Jay

Mike... I can not give you an actual cost but only an estimate for my heating system. First remember, even though you are in a much colder climate than I (I know you are) there are some things that are the same. When I have weather in the teens for days it is the same as by you(in the teens that is). I have a remote reading temp probe in with my trees. I find the temp on the shelf does not drop that quickly or that deep. The unheated garage attached to the house does get some heat from the fondation. So if you can construct an inclosure useing one side of the house as one side of the inclosure it will help. Now for the cost...the copper tubeing used was perhaps a few dollars, the anti freeze was automotive and I only used a cup or two and the electric heat tape(with stat) was about $10.00(I think). The heat tape comes in various lengths... the longer the tape the more it costs to buy and to run, that said, the cost of running this heat tape is VERY LITTLE. It draws milliamps if I am correct. You could also insulate the pipe to the shelf to keep the pipe warm. If you use this method be sure it only cuts the degree of cold and does not eliminate it....you do want the trees and roots to get down to at least the 30's.

__________________
A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing