Palm Trees need potassium in large amounts. Potassium deficiency is perhaps the most widespread and serious of all disorders of palms. Usually you potassium affects older leaves on the palm tree and than progresses to the newer leaves as the problem becomes more severe. You will notice translucent yellow to orange spots. There also can be black or necrotic spotting.
Leaflets will usually have areas of necrosis (dead tissue) along their margins and tips. Symptoms are worse at leaf tips and margins and less severe at the base of the leaves. As symptoms progress, tips of leaves will appear withered, burnt and frizzled. The midrib typically stays greenish-yellow for a period of time.
Potassium deficiency result can be fatal to the palm tree. Potassium tends to leach rapidly from sandy soils, and it is in these soils that potassium deficiency is more apt to occur. In heavier clay soils, the rate of potassium leaching is reduced. Deficiencies in clay soils may be more due to insufficient potassium fertilizer applied. Palm trees that are in lawns may become potassium deficient as many turf grass fertilizers are high in nitrogen, but low in potassium. Palm trees need fertilizers that contain potassium as high as or higher than the nitrogen content. Fertilize all palm trees separately from the lawn.
Prevention and Treatment of potassium deficiency
Potassium deficiency can be prevented and/or treated with applications of sulfur-coated (slow-release) potassium sulfate, but slow-release magnesium should also be applied simultaneously to prevent potassium to magnesium imbalance. If treated, necrotic leaves will not recover, but new growth should become healthy and will eventually replace the injured leaves.