Fruit tree pruning lessons begin Saturday

As soon as the leaves drop from your fruit trees, you can begin to prune them. On Saturdays, Dec. 12 and 19, I will be conducting peach and nectarine pruning classes at the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas. The class will be held from 10 a.m. to noon both days.

Classes on pruning apricot, plum and related fruit trees, such as pluots, will be held on Saturdays in the beginning of January. Apple and pear pruning will be toward the end of January. Grape pruning classes will be conducted in March. Grapes are always the last thing we prune in the orchard.

Q: I have two plants that I am not sure how and when to clean up. Red Mexican bird of paradise is now getting to the end of flowering time and it has large stalks, some with seeds and some have lost their seeds. Red yuccas also have grown and the flower stems are getting droopy on some. When is a good time to cut them back?

A: You can cut the red bird of paradise to the ground in the spring to renew it. Follow that with a fertilizer application high in phosphorus. Remove seed pods as they develop so the plant does not reseed itself into the landscape.

Red yucca flowers can be cut back to their base with no problem. I would do it after the blooms have finished but before the capsules form unless you want the capsules for some reason like flower arranging.

Q: How can I get rid of borers in my peach? I’ve noticed the trunk has lots of hardened sap spots, especially on upper surfaces where it branches. I’m assuming it is borer damage.

A: On peach, this is most likely the reason. Not necessarily so on plum.

This winter you can cut out the bark covering the damaged area with a sharp and sterilized knife. We do this at the orchard to determine the extent of the damage and remove hiding places for this insect when it emerges in the spring.

Usually the damage is on the west- and south-facing upper surfaces of larger limbs. Typically this is due to sun damage to those limbs. You will continue to cut out the dead bark with a knife down to the fresh wood.

Make sure the area that you have cleaned is free of dead bark and the living wood is exposed. If the damage is greater than half of the circumference, then consider removing the entire branch. The branch then should be removed at its source, or point of origin, leaving no stub.

Paint the upper surfaces of all large limbs with diluted white latex paint. Dilute the latex paint with at least an equal amount of water. Also paint any exposed large branches that face west or south. The diluted latex paint helps reduce the amount of damage to the limb by our strong desert sunlight. Wood damaged by sunburn attracts these boring insects.

Q: You mentioned “whitewashing the tree.” What is your mixture for whitewashing?

A: In years past, whitewash was a mixture that included hydrated lime. It was the same mixture used to whitewash fences.

You can substitute white latex paint for the old-fashioned whitewash. The mixture is water and white latex paint using at least a 1:1 mix of water and latex paint. The water content can actually be higher than that. It just has to put a white layer on the bark.

It is applied to the surfaces of trees that are subject to sunburn the most. Paint limbs 11/2 inches in diameter or larger on the upper surfaces facing these directions. Paint the trunk as well, particularly on younger or newly planted trees.

Q: I am attaching two photos of my apricot tree. It has several branches with only a few leaves and the leaves are turning brown. It seems to be happening to a new pluot tree that is planted about 8 feet from the apricot tree.

A: What is puzzling to me in the pictures are the brown leaves on one branch while the other branches have no brown leaves. This means that the immediate problem is in that one branch, not the rest of the tree. So we would begin to narrow our investigation to that one branch.

If the entire branch has leaves that are turning brown, then the problem is most likely at the base of that branch. If only part of the branch has leaves that are brown, then we would narrow our search to the area of the branch where the brown leaves stop and the rest of the branch has green leaves.

It is most likely physical damage to the branch in the area where we have focused our search. Physical damage, or some sort of destruction to the branch itself, can be from insects, diseases or humans that accidentally break the branch.

The two most common reasons for physical damage are from insects, such as boring insects, or physical damage caused by humans Look for damage to the limb on the upper side facing toward the sun.

Sun damage to apricot is fairly common due to its thin bark. Once sun damage occurs, boring insects usually invade, causing physical damage to the limb. This physical damage restricts water movement to the leaves above the damage resulting in leaf scorch.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at morrisr@unce.unr.edu.