Last month  we looked at different ways by which members of the Memphis Bonsai Society wintered their trees.  Some had left them on stands last year when the winter was so mild and their trees came through just fine.  Others took their trees off the stands and placed them on the ground in a protected place.  Still others did the same but took special care to protect the root systems by either placing mulch or leaves over the pots and planting media.  Others brought their plants in to a well lit  garage for protection and then there are others who have greenhouses . 

 Some of the greenhouses are unheated and at least one that I am aware of has a heated greenhouse.  That doesn’t mean that he keeps his temperature up reasonably high. 

The temperature control is set at about 40 degrees, enough to keep the potting media from freezing but not that warm to break dormancy.

 
What have I?  Well, my trees are in a restricted area and when the winter winds and cold are around the corner, I put up my 3/4 inch PVC frame and then cover it with white plastic. 

My “greenhouse” stays open most of the time (held open with clamps) except if the temperature is going to drop below freezing.  Then I close it. 

 
If the temperature is going down into the low-to mid twenties, I not only close it but I have an electric heater that I place inside.

This has worked for me.  What do you do to “winterize” your bonsai trees?? 

Drop  me a line and then it can be shared with others.

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A couple of questions for you.
1. Why do we need to keep the root systems and potting medium from freezing?

2. Why do some folks use a clear plastic cover and others use a white plastic cover for their greenhouses?