When covering plants to protect them from freezing temperatures, plastic is perfectly fine to use…as long as the plastic doesn’t touch the foliage. Plastic will transfer the cold to leaves touching or almost touching the plastic. Tender leaves will be damaged by the cold.

Cloth sheets might not transfer the cold to leaves touching them because of the little air pockets in the fabric that slow down the movement of chill within the fabric. But wet cloth, absorbing dew or rain, loses much insulation value.

For the occasional quick cover-up, cloth is fine. If it’s frosty, prop up the cloth on supports to raise it above the foliage. But for longer-term protection, I use plastic. Plastic, of course, sheds water. There have been times when I’ve used blankets sandwiched between layers of plastic for the best insulation value. Blankets cut off the light though, so this was done only on super cold nights or when the power went out, and the miniature Christmas lights that warmed the space couldn’t work. Photo—a few pots of tender plants in a plastic bubble, with indoor/outdoor incandescent lights.