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Farm Advisors Warns Gardeners to Irrigate in Dry Winter...But Hold Off on the Pruning
By E.A. Barrera
Winter months often seem to have one advantage - we think we can save on our water bill when it comes to watering our plants and trees.
However, according to farm adviser and horticulture expert Ed Perry, this is a bad habit.
"In low rainfall years, a winter irrigation is often a good idea, especially if the trees have not been well watered since last summer. Many soils - especially sandy soils - are dry right now at 2 to 3 feet deep," said Perry.
Perry, a farm adviser for the University of California's Cooperative Extension said watering trees and plants is critical in winter due to the fact that roots begin actively growing four to six weeks before the buds in the tops of trees begin growing.
"The roots of some species, like almonds, have already begun growing. Roots grow poorly, or not at all, in dry soils. This results in water-stressed trees that grow poorly, produce poor crops and are more susceptible to insect and disease pests," said Perry.
Perry noted that dry soil is difficult to hydrate and often requires a lot more irrigation so as to allow water to penetrate the soil sufficiently for the entire root zone.
"Your goal should be to thoroughly soak the soil around your fruit trees to at least 3 feet deep," said Perry. "Another good reason for irrigating now is to move fertilizer into the root zone. If you applied your fertilizer early this winter and have been waiting for rain to move it into the root zone, an irrigation now will accomplish the same goal."
Perry said flower and leaf buds should be well supplied with nutrients - especially nitrogen - when they begin growing in spring.
"This means that the fertilizer which you apply in the fall must move into the soil, be picked up by the tree's roots, then move up in the tree to be utilized by growing buds in the spring. All of this may not happen unless it rains, or in a dry year, unless you irrigate," said Perry.
Perry said citrus and avocado trees would benefit from an irrigation, since these subtropical trees are evergreen, and continually transpire some water all year long, even during the winter months. He noted that subtropical fruit trees injured by the freezing temperatures in January would require careful and consistent irrigation to help them recover from the cold.
Perry also said it was important in a cold dry winters to avoid pruning these types of trees, since the true extent of the damage might not be understood until the spring arrives.
The frost injury to plants depends upon a number of factors, including species, age, health, soil moisture and location. Frost injures plants by causing ice crystals to form in plant cells, making water unavailable to plant tissues and disrupting the movement of fluids, he explained.
If a 1- or 2-year old citrus tree has been killed almost to the ground, it's important to determine whether the dead wood extends below the bud union, something best done in April or later.
Fellow UCCE citrus farm adviser Ben Faber said the only treatment that should be applied rapidly after a freeze is whitewashing the trunks of the trees. According to Faber, the most severe damage following a freeze comes from sunburn of exposed twigs and branches after defoliation.
"If a tree has been defoliated, paint or spray water-diluted white latex paint to protect the bark from the sun," said Faber.
Both Faber and Perry advise owners of deciduous trees to decrease or withhold nitrogen fertilizer applications with severely damaged citrus trees and remove the frost-damaged fruit. They said removing the damaged fruit would relieve stress from a weakened tree.
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