Answer: Although it seems that every nursery in the Valley sells queen palms, they are a marginal plant in the low desert, suffering from our weather (hot, dry, windy) and from iron chlorosis and salt burn. Iron chlorosis is a problem in the desert for non-native, non-adapted plants. Overwatering, combined with heavy summer or winter rains, can promote root rot, fungal diseases and iron chlorosis. Chlorosis is recognized by new leaves that are yellow, while the veins remain green. If the condition is severe, the entire leaf may be yellow. Queen palms, pyracantha, bottle brush and silk oak trees often suffer from chlorosis.
Although iron may be present in the soil, it is not always in a form that plants can use. Overly wet soils are depleted of oxygen. (As water fills in the minute spaces between soil particles, air moves out.) Plant roots need oxygen to absorb iron in the soil. To help prevent chlorosis, always water slowly, deeply and infrequently.
Desert soil has a high pH (alkalinity), which also inhibits iron absorption. If you are using correct irrigation methods and symptoms are still present, apply iron chelates or ferrous sulphate to the soil. Both are readily absorbed by a plant?s roots.
Yellow and browning leaves can also signal salt burn.Often times with drip systems, they are not timed to run long enough to provide a slow, deep watering. When leaves brown around the edges, the problem is often salt burn. This is common in our area with low rainfall, alkaline soil and water high in salts. 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, slowly and usually infrequently.
It's difficult to say "how much to water" since soil conditions, weather, your microclimate, irrigation system, etc. all play a part. With a newly installed tree, you should probably water once a week, and make sure the water penetrates 2-3 feet deep out to where the root zone is expanding. Use a pointed stick or piece of metal to push in the soil. It will move easily through moist soil and stop at dry soil. After five months and coming up to cool weather, you should be able to water your palms once every two-three weeks. At least once a month, water deeply enough to "leach" or push salts well below the root zone. Frequent, light "sprinklings" or short time spans with drip irrigation, allow salts to accumulate in the top layers of soil, where the roots are, which is bad news.
Similar symptoms occur when too much fertilizer has been applied. It's generally not advisable to fertilize landscape plants in our summer heat. Plant roots often "burn." I hope this information helps!
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