Question: What do I do the night of the first killing frost or freeze?Answer: What do you do when it looks like the growing season might come to a halt? Many times, if you can pull your plants through that first frost or light freeze there will be several more frost-free weeks before winter arrives to stay.
For a light frost: Frost, which forms on plants’ leaves, just as it does on car windshields, during clear and still, cold weather, can disfigure or kill plants, so take precautions even when temperatures are expected to fall only into the high 30s. Covering plants with lightweight nursery cloth or old sheets can gain several degrees’ worth of cold protection. Move container plants under the cover of porches or beneath eaves.
For an actual freeze (32 F or below): Protect hardy plants (such as chrysanthemums in bloom, also leafy and root vegetables) with lightweight nursery fabric. You’ll gain several degrees of protection from those frost-cloth fabrics when you use them to cover tender annuals such as tomatoes or marigolds. Freeze-sensitive annuals can be protected from hard freezes by covering with plastic suspended away from their leaves. Supply supplemental heat to keep temperatures above freezing beneath the cover. Do not allow their leaves and flowers to touch the cold plastic.