Heat, rock mulch will harm photinias
: I planted a row of red tip photinia between a walkway and the side of my garage to try to grow a formal hedge to break up the mass of the garage wall. In front of the photinia I have a row of lantana that I prune low to the ground. Some of the photinia, especially the ones that get the most afternoon sun, have leaves that appear to be burnt during the summer. They are a brownish or blackish color. The plant is not dead as there are new leaves growing on it, even on the same stems that have the burnt leaves. Do you have any suggestions on what I can do? Does it need more or less water?
A: Photinia will grow here but it will not do well after a few years of growing in rock mulch or in a very hot part of the landscape.
Photinia needs to have organic mulch around it to do well and give it some relief from the heat. It will grow better in an open area rather than near a hot wall or a wall reflecting a lot of sunlight. This is why the photinia with late afternoon sun has burnt leaves. It is just too hot for it and if you have it in rock mulch, it is just plain baking. The plant will begin to recover as the temperatures cool in the fall and spring, but it will really suffer in that location during the hottest part of the summer.
If you have rock mulch, it may be possible for this plant to squeak by if you replace the rock with 3-4 inches of wood mulch. But, it sounds like its location is just too doggone hot and you may have to move it to a new location. Then you can replace the photinia with something that can tolerate the heat better.
Another option is to give the photinia shade during the afternoon, but rock mulch will still be a problem.
As far as watering, they should be watered like any other high-water use woody plant in the yard. In the hottest part of the summer, watering two to three times a week so that water penetrates 18 inches down from the soil surface is adequate if the plant is mulched.
Rock mulch will increase a plant’s water use and it may have to be watered more frequently than when planted in wood mulch.
Q: I moved into a home with a lot of sago palms. Most of them are very healthy and dark green. Two of them did not seem to be doing well. One was up against a west-facing wall and I think it was getting too much heat. The other was also facing west and always seemed to be greenish-yellow. I had them both moved to a better spot with no radiant heat and less direct sun. The outer leaves are still yellow but the inner new leaves are nice and green.
Should I cut off the old yellow leaves now that it is getting cold or wait until the late spring when it warms up? Also, is there a fertilizer or something I can give them that will help them with their transplant?
A: It sounds like you have figured out the problem. They do not do well in real hot locations, western exposures or southern exposures with no relief from the late afternoon sun.
You did the right thing by moving them. Usually all I recommend when transplanting is to make sure that you have adequate phosphorus surrounding the roots and that the soil in that location has been composted with lots of organics. Inorganic surface mulch that decomposes also is going to help.
Some people use supplements such as vitamins and hormones but I have always felt they were unnecessary.
As far as the yellow outside leaves or fronds go, I would be inclined to remove them. If there is not much green on them, they are not doing the plant any good and they look bad. The yellow leaves are a natural response from being transplanted.
Q: I sent you a couple of pictures of the bark on my 24-inch box California pepper tree. The tree was planted about three months ago. Is some type of protection needed?
A: To me the trunk appears to be maturing and that is the reason it is turning brown.
Those getting my newsletter can see what the picture the reader sent. I also included a picture of a mature California pepper tree trunk. The smooth trunk on your tree is a juvenile trunk. As the trunk ages it produces bark that peels off, which is termed “exfoliating.”
My newsletter is free of charge and has no advertising. Contact me at morrisr@unce.unr.edu for a complimentary copy.
Q: I did a search on the Internet for killing or getting rid of borers in Las Vegas. I have two pomegranate trees that have been infested and I believe are going to have to be replaced. Before giving up on them, I wanted to see if there was any help for them. Either way, I do want two pomegranate trees. I wanted to know how to naturally kill or rid my trees of these borers. If I am unable to get rid them with natural products, what safe pesticide would work?
A: I have never seen borers in pomegranate trees. For this reason, I am suspect that your trees have something else going on rather than boring insects.
The nice thing about pomegranates is that they come back so well when cut. Most people grow pomegranates as a multitrunked tree or a shrub. In either case you should be able to cut the trunks back to the ground and they should resucker from the base.
If you do have borers in the pomegranate tree, it is most likely because of poor management, primarily watering and fertilizers. Pomegranates perform very well in the heat but even perform better and produce more and higher-quality fruit if they are irrigated adequately, fertilized appropriately and pruned for better production.
Pomegranates would be irrigated much like any other fruit trees in the landscape and fertilized a single time around February or early March.
To solve the borer problem in your pomegranates without pesticides I would suggest cutting them back and let them regrow. You will lose production for a few years from those areas that are cut back severely since the trees produce fruit from growth on old wood, but they will still produce earlier than replacing them. That is the price you will have to pay.
I would not recommend the use of any pesticides for borer control in pomegranates.
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.