Regional Gardening Reports :: National Gardening Association

In the Garden:
Southern California Coastal & Inland Valleys
December, 2006
Regional Report

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Move succulents in pots under cover for frost protection, and keep them barely moist all winter long.

Preventing Frost Problems

We're officially into our frost-possible weather zone (Thanksgiving through January 31), so here are some ways to lessen the likelihood of extensive damage should we get a hard frost. I haven't had one in Pasadena in three years, but friends in Long Beach did have real damage last year ... go figure!

Wrap trunks in newspaper, and cover the foliage with plastic sheeting. Support the plastic away from the foliage, as it will conduct the frost damage to the leaves it touches. Also, a low-wattage (40W or so) light bulb hung in the center of the tree (or several in larger trees) should keep it snug enough over really cold nights. Cold soil and dry winds can stress citrus trees, causing the rinds of ripening fruit to develop bleached blotches and leaves to turn yellow where the sun strikes.

Cacti and Succulents
Container plants should be moved under cover for protection from cold and rain. Remember to water them each month, though, since that's all they'll get. Even so, they're dormant and won't need much water -- and no food.

Tender Subtropicals
Bougainvilleas, fuchsias, and hibiscus must be covered when frost threatens. Use large cardboard boxes, or drape old sheets or tarps on stakes over them. Keep the plastic away from the foliage, or the foliage may freeze more readily.

Watering and Misting
Because cold air will keep evaporation down, plants will need less water. But plant roots are not very efficient at bringing in moisture during cold weather, so be sure they get well watered at least once a month. If you're unsure if water is needed, dig down 6 inches or so; if it's heavy and gummy and you can squeeze it into a ball, don't water; if it's light and crumbly and a fistful falls apart, do water.

Misting outdoor plants will minimize frost damage. Sprinkle plant foliage the night before a frost to put a thin layer of water on the foliage overnight, which will insulate the leaves from severe frost damage. The next morning, lightly sprinkle the foliage again to wash away the frost before the sun hits it, when the actual damage occurs (the melting ice crystals "explode" plant cells, and they leak to death).

Since water in outdoor hoses may freeze by early morning, keep enough water inside the house or another protected area to use for the morning sprinkling. The drawback of this method (besides being labor-intensive and requiring strict attention to each evening's weather) is possible waterlogging of the soil surrounding the plants. Because this sprinkling for frost protection may continue for several days at a time, be careful not to water too much each time, or the accumulated water may drown the plant. For the best coverage of foliage with the least amount of water, use sprinkling cans with fine-spray nozzles, or misting spray bottles.

Even if frost damage does occur, don't prune plants until they leaf out and you can see precisely what damage occurred. You'll be surprised just how much of those scraggly twigs are alive after all!

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