Treatment of nutritional deficiencies is a last resort; prevention is superior to correction. Practice proper fertilization, maintain good drainage and aeration, implement sound horticulture practices such as proper planting depth and irrigation, and maintain proper pH. 

Macronutrient deficiencies usually can be treated by simply supplying the needed elements to the soil. As noted earlier, micronutrient deficiencies are usually traced to a cultural or environmental cause prior to corrective application of fertilizers. Failure to do so will result in only temporary and incomplete control of the deficiency. 

Remember that many micronutrient deficiencies occur because of damaged or inadequate roots. Soil applications of fertilizers may, therefore, be very slow to correct the deficiency. In these cases it may be more advantageous to apply a foliar spray of micronutrient along with a soil application until complete recovery is achieved.

In many instances, non-nutritional disorders may exhibit symptoms similar to those of nutrient deficiencies. 

Since symptoms of potassium and magnesium deficiencies occur on older leaves, they may be confused with those of naturally senescing leaves. However, the orange or yellow translucent flecking or spotting (potassium deficiency) and chlorosis (magnesium deficiency) occurring toward the tips of the leaflets or leaf segments with the center of the leaf and rachis remaining green distinguish the nutrient disorders. Also, the naturally senescing leaves usually become uniformly yellow and brown throughout, and the discoloration is not concentrated toward the tips. top of page

Palms will suffer quickly due to insufficient or incorrect fertilization. Since they are relatively slow-growing plants, palms take longer to recover than plants when suffering from a nutrient disorder. 

The prolonged, relatively cool winters and springs of coastal California further slow any recovery. A good fertilizer program is essential to establish a palm rapidly in containers after repotting or in the ground after planting. 

Controlled- or slow-release forms of nutrients from either organic sources (blood, bone, or fish meal) or chemically treated (sulfur- or resin-coated) inorganic forms are preferred to highly soluble, quick-release inorganic materials, since the former provides a steady stream of nutrients over a longer period rather than the short bursts of fluctuating dosages of the latter. 

Palms seem to respond best to a steady, constant supply of nutrients, and it is no wonder since this is how they are provided in the wild from the decay of organic matter in the forest. 

Controlled-release inorganic fertilizers are formulated with specific release periods, such as 3, 6, 9, or 12 or more months at soil temperatures of 22 C. (70 F.). Higher soil temperatures speed up the release of nutrients and lower ones slow it down. top of page

The best fertilizer ration for palms is 3-1-3 (for example, a 15-3-15 or 12-4-12) of nitrogen, phosphorous, and potassium. It is preferable that the fertilizer have nitrogen and potassium in the controlled-release form to prevent potassium deficiency and subsequent problems related to nutrient imbalances. 

For established plants, apply a complete, controlled-release fertilizer of 3-1-3 ratio, preferably one containing magnesium and micronutrients. Broadcast at the recommended package rate and frequency, mixing into the soil thoroughly where possible and water it well. Take care not to place the fertilizer against the stem where newly emerging roots may be injured. If using soluble or rapid-release, inorganic fertilizers, a good rule-of-thumb is to apply half the recommended label rate but at twice the frequency. Soluble fertilizers need to be applied more frequently to light, sandy soils versus heavy, clay ones. The total amounts of soluble fertilizer needed will differ over a period of time. 
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