The decision about what action to take with impending fall frosts can be complex. That’s probably why many simply throw a cover over their warm season crops (peppers in photo, tomatoes, etc.) and hope for the best.
The rhythm of the seasons with shortening days and cooler temperatures really speaks against fighting the trend. Harvesting tomatoes and letting them ripen indoors as discussed in the September 17 post may be a better choice in many ways. Cold temperatures destroy flavor and chilling injury decreases “shelf life” of the fruit leaving them open to decay. Room temperature indoors eliminates both problems.
Tomatoes will not be setting more fruit in cool temperatures so saving green plants is not productive from that standpoint. Concentrating on soil improvement by removing warm season plants to the compost bin and planting a cover crop as discussed last week may be a better use of a gardener’s energy.
Cool season greens planted in mid-summer (kale and mesclun in photo) tolerate frosts well. They may be more productive for the water applied in fall than warm season plants. Maturing root crops will also survive initial frosts and store well in the garden until dug for use.
Covers can perform well in radiational frosts experienced under clear nights. Cloth (photo left) will trap soil heat with the plants and is fine as long as it doesn’t get wet. Wet cloth loses heat due to evaporative cooling. Plastic traps heat and doesn’t have evaporative losses due to moisture but must be removed promptly the following sunny day to avoid cooking plants. Do remove any cover the next day to allow the sun to warm the soil again.
See CSU Extension Garden Note on Frost Protection and Extending the Garden Season for more extensive information including comments on use of space blankets and Christmas tree lights under covers.
Photo credit: Plastic to cover peppers, mid-summer planted greens, fabric covered tomatoes, all credit Carl Wilson