tmo wrote:
"Last night, with the weather forecast predicting lows in the 40s, a
friend suggested I cover my tomato and pepper plants. I put dry cleaner
plastic over the tomatos and glass jars over the peppers."

Plastic is not a good material to protect plants from frost or freeze.
Cold is easily transmitted through it and plant tissue will be damaged
where there/s direct contact.

Glass cloches work well, but should be removed or propped open in the
morning to prevent overheating during the afternoon.