Question: We have two Mexican fence posts, one in the back yard (eastern exposure) and one in the front yard (western exposure). They were both planted in 2010 and were mature when planted. The backyard fence post is doing well, but about six months ago the front yard fence post started to turn yellow. I’ve attached pictures for your review. We cover the fence posts in the winter when it gets below freezing and I hand water it once per week during the hottest months when we do not get rain. Our local “master gardener” group suggested that I lightly fertilize it at 50 percent strength with all purpose, 10-10-10 fertilizer, which I have done twice over the previous four months.

As you can see in the pictures, the newer, smaller posts are green and seem fine. It’s the taller posts that are problematic. They have improved their color slightly since the fertilizing, but still look mottled. The master gardener group also suggested that fence posts do not do well with western exposure, but it has been fine in this location until recently. We live in SaddleBrooke at an elevation of approximately 3,400 feet.

Answer: While the damage in the photos appears to be sun related, it may also be water related. Since the plants have been fine for six years, I am concerned it’s the latter. Based on your watering schedule and the age of the plants, I think you are overdoing it. Too much water can cause cacti to rot. I can’t be sure from the photos if rot is occurring, time will tell. I recommend you back off the watering to once per month and make sure it is a deep soak.

Question: I live in a small townhouse without space for a garden, so I plant my tomatoes in large pots, using Miracle Grow once a week. The plants get seven to eight hours of sun each day. The vines are luxurious and blooming, but flowers fall off or dry up. Can you tell me what my problem is?

Answer: Tomatoes and many other plants produce more flowers than they can set fruit, so dropping flowers is a normal occurrence. The problem you are having lately is likely associated with our weather.

Once the temperatures exceed 95 degrees or so, the pollen in the flowers is greatly reduced and less viable and temperatures over 100 degrees for a significant amount of time means fruit set isn’t possible.

The best time for tomato production in these parts is the spring and fall, so you might wait until then if you want to keep your current plants alive or start over at the end of the summer.

Question: Suddenly, agaves are drooping and some have wilted almost to the ground. Is this normal during extended high-temperature periods? I’m also assuming that the drooped limbs should be removed since returning to an upright position seems impossible. Is this correct?

Answer: Agaves are succulent desert plants, so it’s not normal for them to droop dramatically. If they have been without any water for a long time, you might see some wilting. Sudden drooping and wilting of agaves in the scorching summer is often a symptom of infestation by agave weevils (Scyphophorus acupunctatus). These insects feed on the interior of the plant at ground level and are associated with rotting that causes the plant to collapse to the ground.

The best remedy when this happens is to remove the plant along with any weevil grubs and adults you may find while digging it up and dispose of them in your trash. These weevils are very common and it would be impossible to eradicate them, but you can reduce the population somewhat. If you have specific agave plants nearby the ones that are infested that you want to protect, there are insecticides labeled for landscape plants that can be used as a soil drench. Some species of agaves appear to be more desired than others. The Agave americana is one that seems to draw more than their fair share of weevils. So, you can experiment with different agaves until you find a selection that allows you to fear no weevil.

Question: I have a 7- to 8-year-old desert willow in the front yard that started growing strange clusters of short, clumped leaves and seed clusters last year after its first spring bloom, and it didn’t bloom again all last year. I did not water it enough last year and thought that might have caused the problem. This spring I paid more attention and have watered it consistently. But after blooming perfectly once this spring, it’s growing these odd clusters again, and no flowers. None of the nearby desert willows have this problem. What do you think the problem might be and can it be solved?

Answer: The short, clumped leaves are sometimes referred to as a witch’s broom. They can appear on a variety of trees and shrubs for a variety of reasons, including feeding by mites, insects such as aphids, fungi, bacteria and environmental stress. Looking at the plant parts under a magnifier can help rule out the insects and mites. The other suspects are more difficult to pin down unless you can recall specific events at the time of the odd growth, such as extreme weather events, herbicide use nearby, etc. The microorganisms require laboratory testing, which is often expensive and not always conclusive. In the end, the problem might not be solved and it might go away on its own. Frustrating, to be sure, but fascinating as well.

Peter L. Warren is the forest health program coordinator for the Arizona Department of Forestry and Fire Management. Questions may be emailed to tucsongardensage@gmail.com