Photinia in Rock Mulch Has Discolored Leaves

Q. Firstly, I enjoy reading your column and have learned many
gardening tips with great results. Since moving into our home three years ago, the Photinia or
Hawthorne patio tree has a recurring problem with discolored leaves, usually in the
spring and fall. It has been treated with Bayer Disease Control, Dormant Oil
and Ironite as recommended by others, along with the normal seasonal
fertilization.  There are three, 4 gph
emitters. Hopefully, from the photos, you will be able to shed some
light on the problem.

A. I am sorry this is such a late posting back to you. What you
have here basically is a nutrient deficiency problem. If these problems get to
advanced they can be difficult to fix. When they’re caught early, it is
relatively easy.

Much of this problem has to do with the soil and the use of
rock mulches around certain plants that are not very tolerant of the soil
conditions that develop under rock mulch. What basically happens is that the
good stuff in the soil I like to refer to as organic material has essentially
disappeared.

When plants are grown in rock mulches there is nothing decomposing
and giving back to the soil and the soil becomes what we call “mineralized” or
void of organic material. Organic material in the soil is very important to
some plants. Photinia is one of them. When these plants are first put into the
ground the soil is modified usually with some sort of planting mix. This
planting mix is usually organic in nature.

This organic material modifies the
soil as it is decomposing and provides many benefits to the plants that help to
improve its general health. As this organic material decomposes and is lost
over a period of 3 to 5 years, these benefits disappear and the plant health
begins to diminish.

The leaf yellowing with green veins indicates a micro nutrient problem, like iron. in our alkaline soils and alkaline water.

This is why would some plants organic mulches that slowly
decompose can be very beneficial. Whereas rock mulches which do not add
anything organic back to the soil tends to be harmful to these plants.

True
desert plants are usually much tolerant of very low organic matter content in
the soil. While other plants that originate from climates where the soils
organic material tend to do poorly growing in rock mulches.

What to do? Obviously if we can add organic material like
compost back to the soil it will help. Usually, however, by the time we notice
it the condition is very advanced and recovery can be slow or nonexistent. The
best thing to do is to get these plants growing back under organic mulches.

Organic mulches do not include bark mulches. These are almost as bad as rock
mulch. Wood mulches decompose and add life back to the soil again. You can pick
up this type of wood mulch free from our Orchard in North Las Vegas and a
Tuesday or Saturday morning. This is a case where you have to drive in and load
it yourself into containers, bags or even a pickup truck.

There is no charge
for this organic mulch. This mulch is made from chipping trees that are cut
down in Las Vegas neighborhoods. Instead of taking it to the dump and burying
it, we have provided a location we can come in and pick it up for nothing. For more information on the mulch at the North Las Vegas orchard and how to get there, call 702-257-5555.

 

You can also try spraying the foliage with a liquid
fertilizer such as miracle Gro and iron sprays. Make sure you use a wetting
agent mixed in the liquid fertilizer so that it improves its chances of
entering the leaves. The wetting agent could be a teaspoon of Ivory liquid in a
gallon of water. Add the Ivory liquid to the water, not vice versa or you’ll
get a bunch of bubbles. This will take multiple applications of the iron
chelate but only a single application of the fertilizer. You can also apply the
iron chelate EDDHA to the soil around the plant and water it in. The only
nursery that is caring it to my knowledge is plant world on Charleston. They
have this iron chelate labeled with my name on it because I recommended so
often. I do not get a kickback or anything else from recommending it. It works
for reasons that would take too long to explain here. So in a nutshell,
surround your plants with organic mulches that will decompose. Spray the plants
with a liquid fertilizer combined with a wetting agent now. Also spray the
plant with iron multiple times about a week apart and include the Ivory liquid.
Apply the EDDHA chelate to the soil now. The last thing to do is cross your
fingers and hope for the best. I hope this helps.