Without prompt treatment, the palms will usually die. K deficiency affects all species of palms, but is most severe in royal, queen, coconut, areca, and spindle palms. Symptomatic leaves on K-deficient palms will never recover and must be replaced by new, healthy leaves. In severely deficient palms, this means replacing the entire canopy which may take 2 years or longer. Foliar sprays with K fertilizers are ineffective in correcting the problem since the amount of K supplied by a foliar spray is insignificant compared to the amount needed to correct.
Magnesium deficiency is also quite common in Florida palms, but especially in Phoenix species.
As with K deficiency, symptoms occur first on the oldest leaves and progress up through the canopy. In severe cases, leaflet tips may become necrotic, but Mg deficiency is rarely if ever fatal to palms. Magnesium deficiency is best treated preventatively since treatment of deficient palms takes considerable time. As with K deficiency, symptomatic leaves will never recover and must be replaced by new healthy leaves. Later, only necrotic petiole stubs will emerge and death of the bud quickly follows.