A warning to all gardeners:
Never mind that Tucson's weather has been warmer than normal this month. We could be shivering through freezing nighttime temperatures by Thanksgiving.
Which is another way of saying that it's time to get out all those frost blankets, old sheets, boxes and paper grocery bags. You need to be ready to protect your cold-sensitive plants.
These include lemons and limes, young citrus trees of all types, exotic cacti, bougainvillea, plumbago, hibiscus, crown of thorns, cape honeysuckle and tropical bird of paradise.
You'll also need to protect flowers such as geraniums, impatiens, begonias, lobelia and alyssum. What to use
Cloth and paper provide the best insulating qualities to hold in heat and protect plants.
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If sheets aren't available, consider buying frost blankets, which are sold in garden centers and nurseries. They're made of non-woven polypropylene, which is lightweight and can be left on plants for several days without harming them.
Newspaper also makes an excellent frost blanket, but it should be several sheets thick to maximize protection from cold.
Paper grocery bags work as frost caps when you place them over the tops of tender plants. Protecting cacti
Cold-sensitive columnar cacti can be protected by putting a Styrofoam cup over the top of each column. The cups insulate and protect the delicate growing tips from cold. About those flowers . . .
Straw is especially well-suited to protecting flower beds.
Use straw bales or bags of loose straw, which are available at feed stores.
A layer of straw scattered over flowers and other growing plants helps to hold in the heat. After the cold snap, the straw can be pulled back and worked in between plants to serve as a beneficial mulch over the soil surface.
If needed, the straw can be pulled back over the plants if cold protection is needed again. Avoid plastic unless . . .
Plastic actually conducts cold and won't protect your plants unless you provide a source of heat beneath it.
When you're covering small areas, an incandescent light bulb (60 to 75 watts), contained in a simple utility lamp fixture, can be placed under the plastic frost cover to provide heating.
When you're protecting larger plants such as tender shrubs or small fruit trees, however, you'll need a heat lamp with a higher wattage.
But don't use small-bulb Christmas lights, such as twinkle lights. They don't give off enough heat for adequate frost protection.
Regardless of what you use to protect your plants, it's important that the frost covers are secured properly.
Generally, cold snaps are accompanied by wind, especially on the first night. So if plant covers are not secured, not only will warmth escape from under the cover, but cold air will be forced under the cover. Container plants
Cold-sensitive container plants also need protection, even if they're on a patio. Patio roofs offer some protection, but not always enough.
Either cover the plants or move them to a warmer location — the garage, for example. The heat stored during the day will keep your garage 10 to 15 degrees warmer overnight.
Not all cold-sensitive plants need covering, however. Lantana and desert bird of paradise typically freeze back in the winter but regrow rapidly in the spring.
Freezing back and the resulting pruning of frozen stems actually will keep these plants full and flowering.
» gardening classes
The weekly gardening classes at the Murphy-Wilmot and Oro Valley libraries will be on holiday break through December. Weekly classes will resume on Jan. 9.