Frost on the pumpkin won’t kill it, but it can kill your tomatoes, zucchini and tender summer annual flowers. It can also harm citrus trees. Some plants are meant to live for only one season—you can’t help annuals, such as marigolds, zinnias, most garden vegetables and herbs, but you can keep certain other plants from freezing in the winter by giving them shelter, moving them indoors, covering them with a tarp or plastic, and other simple methods. Subtropical plants such as bougainvillea, hibiscus and some jasmines are examples of frost-tender plants you can help.
Keeping Plants From Freezing
Bring all of your potted houseplants indoors before your first fall frost. Provide them with a sunny, warm environment—a south-facing window is often a good location. Be sure to spray them with insecticidal soap spray to prevent introducing insects into your home. Alternatively, you can move potted plants into a small hobby greenhouse.
Spray tender plants in the ground with an anti-transpirant spray. Examples of plants that you can help with this method include citrus trees of all types, especially the more tropical varieties of lime.
String outdoor Christmas lights all over your frost-tender plants. You can also hang incandescent light bulbs over and near your plants to give enough warmth to prevent freezing.
Cover your plants with clear plastic sheeting, a floating row cover (“Remay”), tarps or blankets. If you can, build a frame to support such materials because frost or freezing temperatures will damage the parts of your tree where the plastic or other material touches it.
Keep plants well watered during cold weather because freezing temperatures cause plants to become desiccated. Also spread a thick layer of mulch (compost, sawdust, leaves or wood chips) around the base of your plants to keep the soil moist and warm. Mulch is especially helpful for bulbs.
Run a sprinkler to cover your plants with below-freezing, moving water. If the water is moving, it cannot freeze, and this protects plants.