In the Garden:
Southern California Coastal & Inland Valleys
November, 2013
Regional Report

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Use diluted interior latex paint to protect deciduous tree trunks from winter sunscald.

Fall Tree Care Tips

Around Thanksgiving our garden soil is finally cooling off and trees and other plants are slowing their growth and beginning to shut down for the winter. It's also the time when our average first frost occurs. The operative word is "average," since in some years we may not even have a light frost. Nevertheless, it's best to help trees go dormant so they'll recuperate from the previous seasons' exertions. Here are some ways to help them sleep through our minimal winter and re-energize for next year.

Protect Trunks
Provide protection for deciduous tree trunks, as the trees can be damaged more by first frosts than by later ones. Sunscald is a problem during the winter, especially on the south- and west-facing sides of young trees with thin bark. Prop up or loosely tie cardboard or palm fronds to the trunks, or paint with inexpensive white interior latex paint diluted with water.

Check Stakes
Anchor stakes and ties to young trees and shrubs to stabilize them against winter winds. Use two stakes and tie loosely and low enough so the tree can sway gently in the breeze. This movement helps the roots grow into strong supports that firmly establish the tree. But don't leave stakes in place more than one year or your tree may end up with a weak trunk and root system.

Pull Back Mulch
Remove mulch from under trees back to the drip line. The bare soil can then absorb the day's heat more easily and release it to the trees at night. This also lessens overwintering of disease-carrying bacteria and insects. Knock down water basins around trees and plants to lessen the chance of sitting water and the resulting root rot. Loosen the soil within the basins so water can penetrate more easily.

Prune Lightly If Needed
Llightly prune top-heavy trees to reduce wind resistance by cutting out whole branches so you can look through the tree; this means the wind can blow through, too. But hold off on heavy pruning until the trees are completely dormant in January.

Protect Tender Trees
Protect tender subtropical trees such as avocados, young citrus, guavas, and loquats from frost damage by watering them well before winter rains arrive in full force. But don't feed them again until late January. Leave citrus fruits on the trees until they're needed -- many varieties become sweeter the longer they're left on the tree.

Plan a Fruit Tree Spray Regimen
Plan your dormant fruit tree spraying schedule to coincide approximately with cool-weather holidays -- Thanksgiving, New Year's Day, and Valentine's Day. Specific cues are the fall of the last leaf (Thanksgiving), the height of dormancy (New Year's Day), and bud swell (Valentine's Day). Spraying at the precise period of bud swell is especially important -- before the buds swell is too early, and after the blossoms open is too late. So, if you spray only once, do it at this time.

Oil sprays smother the eggs of scale insects, aphids, and mites. Lime sulfur and powdered or liquid copper sprays discourage the growth of fungus diseases like peach leaf curl. Choose a copper spray that contains at least 50 percent copper. On apricot trees, use only copper sprays, since sulfur will damage them.

If the rains haven't thoroughly moistened the soil around trees to be sprayed, deep water them a few days before spraying. The oil spray can damage the trees if their roots are too dry. Spray on a cool, dry, sunny day during a windless period to minimize evaporation and drift. Make sure that all leaf, branch, and trunk surfaces are thoroughly covered with the spray solution. Drenching the soil from the trunk to just beyond the drip line is also helpful. Reapply if rain falls within 48 hours of the application.

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