|My Queen palms have recently developed black spots on some of the fronds as well as turning brown on the ends. They receive full AZ sun all day long. Could they need watering more frequently? Currently they are watered 3 times per week for 30 minutes.|
|Salt burn is a common problem on queen palms in the low desert. Even though they are sold in almost all of the nurseries, they really aren't well-adapted to our conditions.
Desert soil and water both contain salts, which can accumulate in the root zone over time. This salt buildup forms where the water stops penetrating. If you ?sprinkle? plants lightly and frequently, salts will build up in the top layers of soil and damage or kill your plant. Deep watering?or leaching?prevents this by flushing the salts past the root zone. Water should penetrate 1-2 feet deep, depending on the maturity of the plant. To determine how far water has penetrated, poke a soil probe (any long metal rod or screwdriver) into the soil. It will move easily through moist soil, stopping abruptly where soil is dry.
When leaves brown around the edges, the problem is often salt burn. Salts in the water and in fertilizer build up over time. Browning usually occurs on the old leaves first. This excess salt accumulates in the leaf edges, where it kills the tissue and the leaf dries out and turns brown. It's important to water deeply and slowly. At least once a month, water deeply enough to "leach" or push salts well below the root zone. Similar symptoms occur when too much fertilizer has been applied. Always water plants thoroughly before and after applying fertilizer to help prevent burn.
I'd start by slowly and deeply watering the palms. I'd hold off on fertilizer for until temperatures cool. Fertilizer "forces" a plant to grow, which can be stressful at this time of year. I hope this info helps!