Palm trees use negligibly more water as they get taller

Q: When should a palm tree be taken down? What is the age limit of palms? Are tall palm trees safe for maintenance? Our maintenance man says we should consider having them cut down because of their age and height. It’s expensive to have them trimmed twice a year.

A: I would agree with your maintenance person. It has nothing to do with water use. Palm trees use negligibly more water as they get taller. It’s really a question of their cost of maintenance.

I don’t know how old these trees will get. I have never seen them old enough to fail from age; they just seem to get taller and taller.

If you enjoy them (their beauty outweighs their expense), keep them. But if you don’t enjoy them anymore, have them removed. The sooner you do that, the less costly it will be.

Q: Your blog, Xtremehorticulture, has been a wonderful resource and source of encouragement. I garden in northern Arizona, and many of the challenges are similar to Nevada: alkaline soil without any organic matter, temperature extremes, limited water, and the list goes on. I have had trouble with a photinia hedge for several years. It was by reading some of your old posts that I finally pieced together what may have happened.

A: Northwestern Arizona might include the Kingman, Laughlin/Bullhead city area and extends down to Lake Havasu. Basically, Mohave County.

You’re right. All or most of our desert soils are low in organics. Salt can also be a problem. The removal of salt is done by flushing the soil with water several times with unsalty water, or what some authors call clean water.

But raising the organics in the soil is a bit more complicated than that. Lowering the alkalinity (or pH) of a desert soil can be done “organically” by mixing organics into that soil. Or, you can leave the organics on top and let water do the work of mixing it.

Organics eventually rot in the presence of water. Organics might include wood chips and root grindings removed from local trees.

Remember that alkalinity (pH) of these units is logarithmic: One unit is the equivalent of 10, rather than only one unit. Laying this type of mulch on the soil surface 3 to 4 inches deep and watering it might lower the alkalinity one full unit, from 8.6 to 7.6 (a lowering of 10).

Other benefits of using any kind of surface mulch (including rock) will lower the evaporation from wet soils, control annual weeds and lower the soil temperature.

Whenever alkalinity or the soil pH is above 8.0, the iron present will be in the wrong form to help the plant. Because of that, the new growth of photinia starts yellowing. That’s where iron soil fertilizers, such as iron chelates and other types of iron fertilizers, can play an important role.

Most granular fertilizers don’t contain any organics and will not help the organic content of the soil. Use of any kind of fertilizer is not considered organic unless the bag or box tells you it is. If it says on the label that it is organic then, by law, it’s an organic source. Organic fertilizers don’t help the organic content of the soil much.

My blog focuses on desert horticulture and was started with weekly postings in 2006. There are now over 3000 entries. This blog is searchable by writing keywords in the box just under the header. No advertising is used to support it. By searching my blog, I am sure you got the answers you needed.

Q: I planted a Fantasia nectarine tree in my front yard last March. The summer heat was brutal. The leaves yellowed and were off by early August. It shocked me by growing a cluster of leaves at the base of the tree — but only at the base. The top branches were bare but not brittle and dead. Any advice on keeping this tree alive?

A: If the branches of the tree are still supple, these branches might sprout new green leaves. There will probably be some that don’t, but dead-looking branches may not be totally dead. To check if they are supple, bend a few and see if they spring back.

Whatever you’re tempted to do, don’t water the tree every day. Give it at least one day’s rest between waterings.

The mulch at the base of the tree should be spread to a distance of about 3 feet from the trunk and 2 to 3 inches thick. The thicker the better.

Remove any mulch touching the trunk and rake it back. The trunk should be 6 to 12 inches free of mulch so that it doesn’t get wet.

Q: A tree at a neighbor’s house has grown out of control over the past couple of years. Is this a sumac tree? You’ll notice that it is extremely close to a block wall. Will this create some problems? Should it be cut down and removed? If it is OK to keep, how should it be pruned?

A: Yes, it looks like African sumac. It looks like it was planted too close to that wall. Trees should be planted no closer than about three-quarters of their mature height away from walls and foundations. I know that sounds like a lot, but large plants need room to grow.

An African sumac gets about 25 to 35 feet tall at maturity, so it should not be planted any closer than about 18 to 20 feet from anything you want to destroy.

I would eliminate that tree. If you want to put a new tree in, plant it about 18 to 20 feet away from the wall. No plants should be closer than 3 feet from a wall or foundation anyway.

About 2 feet of dry soil is needed to prevent root growth and possible lifting. Roots of woody plants in watered areas will eventually lift or crack a wall or foundation. Apply water on the side away from the wall.

Q: My grass is in terrible shape. It has never looked this bad the whole time we’ve been here. It happened after we got those monsoon rains a couple of weeks ago. Why? I thought rain was supposed to be good for the lawn. Will it have to be reseeded?

A: It’s a turfgrass disease. The grass was stressed before that happened. Some turfgrass diseases spread on weakened grass when it’s warm and humid.

Any turfgrass fungicide applied correctly will keep it from spreading. Use a lawn fungicide to treat the area. I prefer a name-brand type when making the application.

You will have to reseed the damaged areas this fall sometime around October as soon as air temperatures drop consistently into the 80s.

Q: I don’t think my golden barrel cactus liked all the rain. Anything we should do or will it heal itself? If it can be saved, how do you suggest saving the side shoots?

A: With that much yellowing and damage, I think your cactus and side pups are goners. Judging from your pictures, that internal rotting started before the rain. The rain accentuated the cactus problems.

All cactuses and succulents need exceptional drainage after planting combined with infrequent watering. Plant them on tops of hills and avoid planting them in low spots. Even if you want cactuses to grow rapidly, watering once a month, when planted in native soil, is often enough.

If you are using an irrigation system, then that plus the rain, is too often for cactuses. For most cactuses, irrigation systems cannot apply water infrequently enough. You are better off watering with a hose, combined with a sprinkler and timer.

I use water to push growth. When I want them to grow, I water them. When I don’t want them to grow, I don’t water them.

I water with a hose no more than three to five times during the year. I use a hose-end sprinkler and timer. I water them for one hour, adjusted to 6 to 8 feet wide, before the sprinkler is moved to a new spot.

For young cactuses that need to increase their size, I water them once a month. I lightly fertilize them once in the spring of the year. For cactuses that are large enough, I water them once in the winter and three or maybe four times during the summer.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.