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

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2275

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

Fall Tree Care

Around Thanksgiving our garden soil has finally cooled 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 my garden hasn't had even a light frost in four years. 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.

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 surfaces of young trees with thin barks. Prop up or loosely tie cardboard or palm fronds to the trunks, or paint with a light-colored, inexpensive interior latex paint (exterior oil paint will clog tree pores, suffocating the tree).

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.

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.

Slightly 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 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 do not 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.

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, and viruses. 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. The foliage and roots can "burn" if there's not enough moisture to help them absorb the nutrients.

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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