Exaco Trading Company Biostar 1000 Premium Insulated 8mm Twin-Wall with Protective Netting Cold-Frame from Amazon.com
As fall temperatures dipped in the Boston area to mid-teens at Thanksgiving, I was concerned that my original plan for winterization of my outdoor bonsai would not be sufficient. It seemed in retrospect that simple storage boxes were not going to be sufficient to protect my trees from Boston’s extreme temperatures. Boxes only provide protection from wind and I wanted protection against hard freezes. It felt like this would be another extremely cold winter, like the prior year.
Armed with this knowledge, I invested in a cold frame. Searching the web for an appropriately sized cold frame, I was lucky to find the Booster 1000, a premium insulated 8mm twin-wall constructed cold frame from Exaco Trading Company. You can find it on Amazon here. Be fore warned, it is not cheap at $216.86. It measures 40″ deep x 30″ wide x 17.5″/20.5″ height (the back is higher than the front). It was difficult to assemble, partially because the instructions are in German and all I could do was follow the pictures. I finally got it put together, but it took close to 2 hours. Frustrating but in the end satisfying that I had a decent system in place to protect the trees. I can also take this apart where each panel meets and store it easily in a storage unit. I will make my own instruction sheet and mark each side with a letter to guide putting it back together next year.
The top of the cold frame can be closed and has 2-panels that slide to provide easy access or air on a warmer day.
I moved the trees into two larger mulch insulated wood crates with stapled burlap on the sides so that air can circulate, and I put thick plastic sheeting on the bottoms of the crates with small holes for drainage. The crates where then placed in the cold frame. Additionally, I have a large plastic basket that resembles wicker. In this, I surround a few trees with mulch, and placed this in the cold frame too.
Trees buried in mulch, in crates or a large basket. The cold frame fit on top of these items
I only need to water them two or three times a week (at most) and this will slow down from January to March. I’m pleased with this setup and it’s easily storable when Spring arrives.