Life is mostly peachy for healthy tree

Q:  I attached a couple of pictures of my peach tree. It’s growing like gangbusters (I did a pretty good job pruning it back after your class), but something is going on with it because it’s dropping leaves and has this brown-leaf-edges thing going on. It had major growth (about 3 feet) after I harvested the peaches this month. Thank you for any help you can give.

A: Let’s cover each issue separately.

First, the peach leaves that are brown and crispy along the edges. This is quite common on peach trees here. It could be a problem called shot hole disease, which is also called Coryneum blight. The purplish spots on your leaves are typically created by shot hole disease infections . I will post some pictures of this problem on my blog and talk about it more there.

There could be some heat stress due to high temperatures, poor soils, salt problems in the soil and even irrigation problems. But generally speaking, if the tree is otherwise healthy and the peaches are good quality, I usually don’t worry about it too much. This is the desert. The problem appears minor, and your tree is in good health.

I also will see shot hole disease develop if the trees were water stressed (didn’t get enough) once or twice during the growing season. Some varieties of peach seem to do this more than others.

You have far too much vigorous growth if you are getting 3 feet of new growth. You should get maybe 18 inches or so. Cut back on how much fertilizer you give your tree next spring. You might even skip one season and just add some iron or lightly fertilize it along with your iron application.

Right now you can remove a few new shoots that are growing back toward the center of the tree or going straight up. Don’t remove too much, and don’t remove old growth. Remove just enough so you see some light getting through the canopy and onto the ground. Light pruning now will not hurt the tree but may make it healthier for next year.

In the winter, when pruning, open up the center to get some light to the inside of the canopy. Remove about 50 percent of the new growth . Focus on leaving growth that is at 45 degree angles. Cut back strong new growth to no more than 18 inches in length.

Q: First, I enjoy reading your column and have learned many gardening tips with great results.

Since moving into our home three years ago, the photinia and hawthorn patio tree have a reoccurring problem with discolored leaves. It has been treated with Bayer Disease Control, dormant oil and Ironite, as recommended by others, along with the normal seasonal fertilizers. Hopefully, my photos will shed some light on the problem.

A: What you have here with the yellow, discolored leaves is basically a nutrient deficiency problem, most likely iron. I know you applied iron, but you did not use the best form of iron for our soils. If these problems get too advanced and the leaves turn all yellow and begin to scorch or drop off, the plant can be difficult to fix. When the plants are caught early in their yellowing, it is relatively easy to fix.

Much of this problem has to do with not amending the soil enough at the time of planting and the use of rock mulches around plants that are not tolerant of desert soils. Both of these plants are not very tolerant of desert soils or rock mulch.

What basically happens is that the good stuff applied in the soil at planting, which I like to refer to as organic material, has essentially decomposed and disappeared. When plants are grown in rock mulches there is nothing decomposing and giving back to the soil and the soil becomes “mineralized” or void of organic material.

Organic material in the soil is important to most plants. Photinia and hawthorn are two of them. When these plants are first put into the ground, the soil is usually modified with some sort of planting mix.

This planting mix is usually organic in nature. This organic material modifies the soil as it decomposes and provides many benefits to the plants that help to improve its general health. As this organic material decomposes and is lost during a period of three to five years, these benefits disappear and the plants’ nutrition and health begin to diminish.

This is why organic mulches that slowly decompose can be very beneficial. Rock mulches, which do not add anything organic back to the soil, tend to be harmful to these plants.

True desert plants are usually tolerant of low organic matter content in the soil, while plants that originate where there are higher levels of organic material in the soil tend to do poorly growing with rock mulches.

What to do? It will help if we can add organic material, such as compost, back to the soil around the roots. This is difficult to do with established plants. You can try removing the rock mulch and replacing it with 4 to 6 inches of organic mulch, and it will help over time.

In the meantime, you might try spraying the leaves with iron sprays in the early morning hours before it gets hot. You will probably have to do this five or six times, a week apart, to see any results.

Use a wetting agent or “spreader” with the spray to help get it into the leaves. It is a liquid that helps make the spray “wetter” and helps it enter the leaves along with the iron. A small amount of foliar fertilizer added to it might also help. Use a lot less foliar fertilizer than the label says while it is hot like this.

You can pick up wood mulch free from the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas every Tuesday and Saturday morning before noon. You have to drive in and load it yourself into containers, bags or even a pickup.

There is no charge for this organic mulch. Call the Cooperative Extension office at 702-275-5555 for directions and more information.

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.