I have a 3-year-old oak (from a stray acorn) that's growing 4 feet away from my 7-foot navel orange tree. Although I appreciate the shade this fast-growing giant provides, I do not want to sacrifice my dying navel orange.

Half of the orange tree (facing the oak) is completely bare and has stopped branching for the past two years. I also noticed more yellowing of leaves and less fruit yield.

Is it possible to have both plants co-exist? If I have to choose, the uninvited oak must go. What is the best method of eradicating it?

– Nick Tran, Sacramento

According to UC master gardener Bill Pierce, citrus need a minimum of six hours of direct sunlight each day to grow properly. Your tree will not get this if you allow the oak to remain.

The easiest way to eliminate the oak is to cut it down and then dig out the roots immediately below the trunk. The other roots can be left in the ground.

The next step: Restore your orange tree's health.

"Yellowing" can mean two things. Yellowish leaves indicate that a citrus tree needs nitrogen fertilizer. Yellow leaves with green veins indicate that citrus needs iron.

Mid-March to mid-May would be a good time to apply fertilizer. Buy citrus fertilizer at the nursery. It has the proper amounts of nitrogen, iron and other minerals needed by these trees. Apply it according to the directions on the bag.

It takes about six weeks after the fertilizer is applied for the leaves to regain their deep green color.

Now about the side of the tree that has stopped growing; is it dead?

Limbs and parts of trees can die when they are shaded by other trees. However, a 3-year-old seedling oak is probably not large enough to have caused that kind of damage to half of your tree.

Sometimes a part of a tree or shrub will die when the grafting stock sprouts and sucker branches grow. These branches are first in line to receive nutrients and water through the vascular system from the roots, causing decline to the grafted area.

Sucker growth will not produce edible fruit. It is very vigorous and it has a vast number of thorns.

Check your tree to see if sucker growth has occurred below the graft union. About 6 inches above the ground, you will see a ringlike area on the trunk; this is the graft union.

The tissues above and below this ring will have a different appearance and will be different shades of green. Any growth below the ring needs to be removed, as it is a sucker.

Sometimes the sucker growth is the major portion of the tree and it hurts to eliminate it, but it must be done.

Another possibility is that the main limbs or limbs on half of your tree have been damaged by wind, pets or children and these limbs have died.

Examine all the branches carefully because damage is often not readily apparent when a branch is broken but not severed from the tree.

Citrus also may become infected with California scale, which looks like little red jewels on the branches and twigs and various soft scales that are often whitish bumps. Insects suck plant juices and can lead to the death of twigs and branches.

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