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Pruning citrus is an inside job. Here’s how you can keep your trees healthy

Freeze hits valley crops, but citrus growers think they may escape much damage

East of Fresno, farmers overnight use wind and water to keep crops, from citrus to fruit trees, from being damaged by frost.
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East of Fresno, farmers overnight use wind and water to keep crops, from citrus to fruit trees, from being damaged by frost.

Citrus trees are reputed to need little or no pruning. True, they generally don’t need much pruning but an annual shaping and trim makes harvest easier and helps keeps citrus in good health for years. Citrus can be trimmed either in the winter dormant season or in spring, between harvest and flower set. The timing of spring pruning varies with the citrus variety.

As always with any pruning or trimming project, start by sticking your head into the center of the plant or tree canopy and take a good long look. The interior of a neglected citrus tree will be a mess of crossing branches, lighter green sucker growth with big, nasty thorns and a lot of dead twigs and branches. Sharpen your pruning shears and loppers (citrus wood can be tough to cut), put on your thickest gloves and clear out the congested center, being careful to not remove branches that form the exterior of the canopy.

It’s important to maintain a full exterior canopy on citrus trees so that bees and other pollinators can find the flowers on the exterior more easily and because citrus wood is susceptible to sunburn.

You don’t want to expose the more tender, previously shaded inner wood to direct sun if possible. A full canopy also creates a warmer micro-climate in the interior that helps protect the tree from frost damage. That’s why you’ll see citrus in commercial orchards with full canopies that reach the ground.

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You do want to expose any pest insects that are hiding inside the congested interior to beneficial predators as well as create good air circulation within the tree. Cotton-cushiony scale (looks like tiny cotton balls) and mealybugs are common citrus pest. They can be controlled with sprays of horticultural oil or neem oil. Mature citrus scale look like tiny brown bumps on twigs and stems. Spray horticultural oil in May to smother the immature “crawler” stage of citrus scale.

Trim and shape mature citrus trees as lightly as possible. Shorten aggressive leaders by tip pruning to create a balanced, symmetrical shape and to keep the tree short enough to easily reach the fruit. Remove frost-damaged twigs and branches in spring when new growth appears which makes the extent of the damage easier to determine.

Citrus should be fed three times a year with a high-nitrogen fertilizer such as ammonium sulphate (20-0-0) or a good quality lawn or citrus food that also contains necessary micro-nutrients. (Citrus food is my preferred treatment for any nutrient deficiencies in other trees, as well.) Mature citrus trees need 1 to 1½ pounds of actual nitrogen annually, which is equal to about 5 pounds of ammonium sulfate. Apply one-third the recommended amount of fertilizer in late February, one-third at fruit set, and give the last feeding in late May.

Iris show

The Fresno Iris Society is having an iris show Saturday in the community room at the Sierra Vista Mall, 1050 Shaw Ave. in Clovis. Entries will be accepted from 7 to 9 a.m. The public exhibition is from noon to 6 p.m. Admission is free.

Potted iris will be on sale and members of the Fresno Iris Society will be on hand to answer questions.

For more information go to fresnoirissociety.org.

Elinor Teague: etgrow@comcast.net

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