In the Garden:
Southern California Coastal & Inland Valleys
December, 2011
Regional Report

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Cheesecloth or floating row covers aid germination and provide protection from frost.

Frost Protection and Other Winter Tasks

Tender trees and plants need protection from frost. For citrus, which don't go dormant, wrap trunks in newspaper, and cover the foliage with plastic sheeting. Support the plastic away from the foliage, as it conducts frost and the leaves it touches will be damaged. Also, a low-wattage (40W or so) light bulb hung in the center of the tree (or several, for 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. Plant roots are not very efficient in bringing moisture to these areas during cold weather, so be sure that trees get well-watered at least once a month. Because cold air will keep evaporation down, plants will need less water. If you're unsure if water is needed, dig down six inches or so; if the soil is 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.

Cacti and succulents grown in containers 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 like bougainvilleas, fuchsias, and hibiscus must be covered when frost threatens. Use large cardboard boxes, or drape old sheets or tarps on stakes over them. Again, when using plastic, keep it away from the foliage or the leaves may freeze more readily.

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. This 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 as 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 other protected area to use for the morning sprinkling.

The drawback of this method (besides being labor- and worry-intensive) 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 to not water too much each time, or the accumulated water may drown the plant. For the best coverage of foliage with the least water, use sprinkling cans with narrow spouts or fine-spray nozzles, or misting spray bottles.

Shrubs and trees that bloom in January and February will need to be fed to stretch their blooming period. Azalea or gardenia foliage that's yellowish-green needs to be watered with a solution of chelated iron, since the cold weather "locks up" the iron in the soil so the plant roots can't absorb it.

Wait until two weeks after the last leaf falls off of trees and vines before you start serious dormant pruning. But don't clip spring-blooming shrubs until after they've bloomed, or you'll remove this coming year's color. Also wait to prune outdoor fuchsias until they leaf out and you can see just how much frost damage has occurred. You may be surprised at just how much of that scraggly twiginess is alive after all!

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