Get ready for Mother Nature’s cold shoulder
In an average year, our first freeze usually occurs by midnovember. It did not freeze in November this year, but be prepared for December.
The temperatures dropped after Thanksgiving, so now is the time to protect cold-sensitive tropical plants. Bougainvillea, plumeria and purple fountain grass do not need light during the winter, but they do need to be protected from freezes. Oriental hibiscus, geraniums and mandevilla survive the winter better if they receive enough light to retain their foliage.
Containers with citrus plants such as Mexican lime and Meyer lemon can be moved into the greenhouse, but it is usually easier to cover them and other citrus on evenings when low temperatures are forecast. Thirty degrees is low for limes, lemons and grapefruit. Satsuma, kumquats and Changsha tangerines can usually survive 26 degrees. Treat avocados like Mexican lime. They are sensitive to the cold.
Blankets work well to protect plants from freezes, as do commercial coverings called “plankets,” which are round, making it easier to cover citrus trees, especially in containers. Plankets also have steel ringlets to allow for a drawstring to secure the bottom of the covering to the container. As convenient as plankets are, they won’t be enough in a hard freeze. Provide extra protection with a blanket or fabric under the planket in hard freezes.
Plastic only works well if it is used as a tent or if there is a cloth or blanket between it and the foliage. Remember that the area under clear plastic heats up enough on a sunny day after the freeze to fry the foliage.
If temperatures are going to be in the low 20s or below, provide a heat source under the tent or planket. A mechanic’s light with old-fashioned heat-producing bulbs or poultry lamps work well. Christmas tree lights are no longer practical.
Fall tomatoes are always in a race against cold weather. The first freeze of the season is often followed by two to three weeks of mild weather, so if the plants and fruit can survive the freeze, they will have another stretch of time to ripen before the next freeze.
At some point you may have to harvest all the full-size fruit and let it ripen in the house. Use the ripest ones first, and the fruit may last for a month.
I have had great luck with cyclamen maintaining their bloom through freezing temperatures. The foliage is very tolerant of the cold, but the flowers will burn from the cold. Mine are always planted in sheltered locations in full shade, so they are not subjected to temperature extremes. If the blooms do freeze, however, that may be the end of them for the winter.
The conservative strategy is to cover cyclamen at about 30 degrees to protect the bloom. A sheet of Insulate fitted to generously cover the cyclamen bed works well for long narrow beds. Plankets or regular blankets work well for square or round cyclamen beds.
Do not worry about cole crops, greens, onions and carrots. Beets, radishes and lettuce will sometimes have injured foliage from a cold spell, but they usually recover.
Pansies are safe, but we can expect petunias, snapdragons, calendulas and stocks to have a bloom-free period in midwinter. They could be covered, but we do not usually bother.