Queen Palms

Q: Two of our queen palms have died and two others look bad. We used Bordeaux treatments as prescribed by our landscaper, but to no avail. What’s happening?

A: Queen palms are tropical plants that often struggle in the desert’s salty soils, low humidity, freezing temperatures and brutal summer heat, explains Cathy Rymer, Certified Arborist, Master Gardener and water conservation coordinator for the city of Chandler. Weak or collapsed fronds, or fronds that are “accordion pleated,” are an indication of a manganese deficiency. Some landscapers may tell you that this is bud rot, which can be treated with Bordeaux fungicide. However, the University of Arizona plant pathology lab has never confirmed a case of bud rot in queen palms during the last 50 years.

Although old fronds will not rejuvenate, applying a complete palm food that contains manganese over the root zone once a month in summer will help maintain healthier queen palms. Water deeply but infrequently, allowing the soil to dry just a bit between waterings. When the soil is too moist, palms are unable to absorb nutrients, which can result in pale-yellow fronds. Apply water 2 to 3 feet from the palm’s trunk. It should soak 2 to 3 feet deep. The interval will depend on the season: once every seven to 10 days in summer and once every three to four weeks in winter.

Our salty soils also interfere with the absorption of nitrogen and iron. Adding a 3-inch-thick layer of organic mulch on top of the soil will slow evaporation, cool the soil and add nutrients back into the ground as it decomposes. The addition of soluble soil sulfur will help lower the pH just a bit, which should encourage the absorption of nutrients.

Q: We are having a rabbit overpopulation problem at our children’s school. Is there any way to humanely deter rabbits from certain areas without the use of chemicals?

A: The most effective method is to install fencing, says University of Arizona Pima County Cooperative Extension Master Gardener Linda Drew. For details on rabbit control, see cals.arizona.edu/maricopa/garden/html/t-tips/animals/rabbit.htm. The site includes a link to a list of plants that are less palatable to rabbits. However, if hungry enough, there is a good chance they may sample just about anything.

Q: What could be eating small holes in my oranges?

A: The most likely culprit is birds seeking moisture during dry periods when irrigated citrus is lush, colorful and juicy, according to Maricopa County Cooperative Extension Master Gardener Olin Miller. Insects infesting the hole cause a secondary effect, and then fruit begins to rot and fall from the tree.
Clean up fallen fruit so it won’t attract rodents, he advises. You could try covering small dwarf trees with bird netting, but there isn’t a practical fix for mature citrus. Nevertheless, with large trees there usually is plenty of fruit for everyone, Miller notes.