Keeping the plants warm in China

I've written before about the method used to preserve plants during winter. By early December many of the trees are painted white - I was told to keep the trees warm, but I think it is just part of a process. Perhaps there is some fungicide or similar in the white "paint", which is applied before the trees are wrapped in rope.

You can see in the photo above that some of the trees are wrapped in rope. In the fore ground are some trees wrapped in hessian. It is quite curious, but it obviously works as come spring when the coverings are removed the plants spring into life.