Most species of palm trees are prone to magnesium deficiency, which causes the margins of older fronds to turn yellow or orange, while the centers of the fronds remain green. Magnesium sulfate, also known as Epsom salt, can help prevent magnesium deficiency in palms. Once the symptoms of magnesium deficiency appear, the condition is difficult to reverse. Regular applications of Epsom salt and palm fertilizer will provide the nutrients that palm trees need to produce healthy, green fronds, but it may take up to two years for the new growth to replace the older fronds. Although the fronds are unsightly, magnesium deficiency is not fatal. Alternately apply palm fertilizer and Epsom salt every six weeks during the growing season to provide a continuous supply of magnesium sulfate, while avoiding damage to the tree from too much mineral salts.
Apply a fertilizer specially formulated for palm trees, such as 12-4-12 with magnesium and micronutrients, from the base of the trunk to the edge of the canopy at the rate of 1 pound per 100 square feet, or according to label directions. Spread the fertilizer evenly.
Water the fertilizer into the soil so the soil is damp 1 inch deep.
Spread 2 to 4 pounds of Epsom salt around each tree six weeks later, working from the base of the trunk to the edge of the canopy.
Water the Epsom salt in until the soil is damp at a depth of 1 inch.