Friday, December 31, 2010

Overwintering trees - experimenting with some principles

As it is widely accepted, the best way of overwintering the trees that stay outside is to put them on the ground. So, you just take them of their shelves or posts and put them down on the ground. That is the basic principle that Walter Pall thaught us a few years ago. I decided to check the raw phisics behind that overwintering technic.
I prepared two (2) identical thermometers (same type, same model, same manufacturer).
One thermometer was placed 1.80 meters from the ground at the eye sight, fixed on the doorpost. We can call it T(1).
The other thermometer was placed on the ground surface in my garden. (the ground cover is grass - now frozen)
During these  days we've had a few centimeters of snow over the grass (up to 10 centimeters). The second thermometer was forced through the snow, in the upright position, until it reached the ground.
That second thermometer  is T(2).
The measurements were checked at the same time in succession for a week. Sometimes twice a day, in the morning and in the evening.


T(1) -9C...T(2) -3C
T(1) -6C...T(2) -3C
T(1) -5C...T(2) -3C
T(1) -8C...T(2) -3C
T(1) -5C...T(2) -3C
T(1) -6C...T(2) -3C
T(1) -5.5C...T(2) -2.5C
T(1) -4C...T(2) -3C
T(1) -3.5C...T(2) -2C
T(1) -6C...T(2) -3.5C

It is possible to make more measurements but I believe that something can be concluded even now. Temperature is NOT the same on bonsai shelves and on the ground level.
Snow (even that thin cover) can serve as a good insulator in addition to ground level position.
Temperature rarely drops below -3C on the ground level and if it does, that changes are much slower than on bonsai shelves or posts.
So, if you have the opportunity, always put bonsai pots on the ground. If there's a snow, let it cover pots and trees. In addition, you can add more with a showel. That's a perfect way to overwinter the trees in the garden.

P.S. Happy New Year to all of you my bonsai friends.


  1. The measurement here just shows, that snow is a good insulator, as you say - keeping the temperature konstant! Would be interested to see T(1) placed at 2 m, and T(2) at 0.5 m or a coupple of centimeters above the snow level. My guess here is that the results would not be that different as in this case...

  2. Oh yes, that could very easily be true. I agree... :)