GARDENING: Sick lawn in need of some iron

Question: My grass has been looking a bit yellow this year. However, I examined it closely yesterday and some blades are green and others are white. The combination makes it appear yellow from a distance. I have never seen anything like this. What am I doing wrong?

Answer:Sorry this took so long but when I get questions to answer that I have never had before it takes me a while to think through the possibilities. The closest I can come up with offhand is the possibility of iron chlorosis.

The typical remedy is just to apply any source of iron to the grass. The fastest acting would be a liquid application of an iron spray such as an iron chelate. Foliar sprays are quick acting but don't last long, maybe a few weeks at best.

A longer lasting action would be to apply iron as a dry fertilizer such as those fertilizers containing iron along with the other elements like nitrogen, phosphorus and potassium. Or you can apply it dry in a straight iron application like iron sulfate or the so-called acidified mine tailings containing iron.

All of these are available through your local nursery. Of course the best solution is to spray the grass with a liquid application and follow it up with a granular application for a longer lasting effect.

Q: I have a 7-year-old Mondale pine in my front yard. I know that it is not uncommon for pine trees to lose needles, but over the past year I have noticed an increase of brown needles on the interior of my tree. Not only are the needles dead, but upon further examination the majority of the branches (small branches not any large ones) that hold the dead needles snap when bent and that tells me they are also dead. Some of the bark also has taken on a reddish-brown color and some of the bark curls up and falls off. I also have noticed small red ants on the tree. From the outside the tree appears healthy and is producing pine cones. Is all of this normal or should I be concerned about this tree?

A: For pine trees it can be quite normal for the interior needles to die and drop on parts of the limbs that are 3 or more years old, depending on the type of pine tree. The most common reasons for needle death can be from normal old age, as I mentioned, or dense shading and the lack of light on interior limbs.

On Mondell pine, sometimes called Mondale pine, there is an insect called the pine shoot tip moth that causes damage to new growing tips. This moth has a larva that tunnels into the new growing tips and causes this new growth to dieback a short distance, not in the interior. This was a pest on some Mondell pines brought into the valley about 15 years ago, but to my knowledge has not been a problem here since. There are no known disease problems that have been reported here. There is a disorder (called a disorder because the pathologist does not know what causes it) on Mondell pines in the Spring Valley area that has caused top dieback, limb dieback and damage in 2003 during the growing season severe enough the trees were removed. But this was not in the interior of the tree.

The most likely reason for death of needles in the interior are the two I mentioned earlier -- needles growing on older growth and too much shade in the interior. Remember that small branches in the interior can be several years old even though they are small.

Lack of light will stunt growth in the interior and you may have very small limbs that could be several years old. Your comment that the outside of the tree looks healthy tells me that you have new growth occurring, which is a good sign. If this were me I would have the tree thinned by a professional arborist and deep fertilized next winter or late fall. The reddish bark peeling off and ants sounds normal.

Q: How is mildew controlled on grapes?

A: Removing a few leaves around the bunches of grapes, enough to encourage air movement, is enough to substantially reduce mildew without the use of pesticides.

Q: I would like to know how and when to trim the suckers on vitex and cassia.

A: The best and easiest time to remove suckers from any tree or shrub is in early to mid-spring, and it is very easy to do. Starting in the very early spring, the living wood just inside the bark begins to expand. At this time the bark loosens.

Horticulturally, we say that the bark is beginning to slip. It peels from the wood very easily. This is the best time to do the budding and grafting of plants. This is also the time when new suckers can be removed the easiest. As these suckers reach about 3 to 4 inches in length, they can be removed very easily by gently bending them over and pulling them opposite to their direction of growth.

If the suckers are young enough, they will pop out of the stem without leaving a stub, much like the sucker was growing in a socket. If the stem is too mature or it is too late in the season, the sucker will rip the soft bark from the stem as it is removed. Suckers coming out of the ground, attached to roots, will also pop from the root.

Leave the root exposed to the open air overnight before covering it with soil. Do not use pruning shears but rather just your hands. Pruning shears will leave behind a small stub still attached to the stem or root. This stub will be the source of new suckers in the future. This will work on any woody plant, including olive and it is much faster than pruning.

Q: Is Japanese black pine suitable for the Las Vegas area?

A: I consider it borderline. Most books classify Japanese black pine as heat tolerant. I have seen too many of them in really bad shape here for me to say it does well. I've seen good and bad ones in good locations and bad locations.

I do think Japanese black pine needs special attention and should be reserved for intensively gardened spots and not for general landscape use.

Q: My Arizona cypresses are dying at the tops.

A: Ninety-five times out of 100 it's borers. They are extremely susceptible to these guys. I was going to say that if you have Arizona cypress and you don't have borers now you probably will, but that's not a fair statement. A fair statement would be, if you have Arizona Cypress and you don't have borers now, you will. Cut out the dead limbs and enjoy them as long as you can.

Bob Morris is a horticulture specialist with the University of Nevada Cooperative Extension.


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