These bags are black plastic and I can assure you, the bagging doesn't rot the plants. I have bagged hundreds of plumeria over the years. I do leave the bags open. It doesn't matter whether the plants are sitting in a bucket, piled up, or bagged. You want to keep the temperature above freezing. I keep all my plants in temperatures at or above 50 F. Temperatures in the 40's won't harm them though.
