Building a heating bed for overwintering Bonsai and Yamadori

I have used a heating bed for over ten years as the best way to increase the recovery of collected yamadori. The building of my new Greenhouse meant that I could have a new much larger heating bed. This is how I made it.

The whole frame is 12ft x 3ft The Timber was 9”x 2”. There is NO base to the frame, it is laid directly on the stone flags. The Timber is held together with 6” galvanised bolts.

A layer of silver backed ‘bubble’ insulation is laid directly on the floor. I could have used 1” Polystyrene block, but this proved OK.

To ensure that the moisture is retained the whole frame is lined with a Heavy Duty Polythene Sheet, and ‘stapled’ into position, particular attention is given to the corners.

Batons are screwed into the top of the frame to secure the Polythene Sheet, galvanised screws are used.

12 bags of Kiln Dried Sand are used to line the base of the frame, 2” deep. This Sand never ‘hardens’ and is a joy to work with. ‘Builders’ sand is not suitable. The Sand is then saturated with water

The heating cable (80ft long) is placed as shown and covered with a further 2” of Sand.

The completed Heating Bed, the cable is secured to the frame with a cable clip and the whole bed is saturated with water.

The raw yamadori now has a comfortable resting place to recover and thrive.

2 comments on “Building a heating bed for overwintering Bonsai and Yamadori

  1. I just found this by accident, but I have been thinking of doing the same thing. I have a few questions if you don’t mind. 🙂

    What temperature does the cable heat to and how warm does it keep the bed? I assume this allows the trees to remain dormant all winter… ( besides maybe slightly extending the growing season?) — Also do you use this for both pine and deciduous, or just deciduous? — How cold do your winters get? And does this keep your roots from freezing during colder periods?

    Would this work to over winter hardy bonsai that aren’t quite hardy enough for the harsher winters in my climate? I keep several maples and a few others that need extra winter protection and I’m hoping this might help.

    I apologize for all of the questions. Thanks for this post and I look forward to hearing from you.



    • Hi Dan you have answered most of your questions already.

      My winters never really get below -10c I use my heating bed to over winter Mediterranean species such as Olive and Myrtle. I also use to establish early collected yamadori. This ‘kick starts’ the establishing phase of the stock. I do not use to extend the growing season however depending on light levels the trees can come into leaf early… but you do need to watch for tender shoots and the cold top with warm roots.

      The Cable keeps the sand at a steady 7c unless we have a very cold snap before xmas I only turn on my bed after new year. Trees need a cold spell to thrive.

      Hope this helps



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