The best palm tree fertilizer typically has a 2-1-2 or 2-1-3 nitrogen, phosphorous, potassium (N-P-K) ratio. While other fertilizers may work fairly well for palm trees, fertilizers with these ratios give the tree the best chance at being healthy longer. If a tree is showing signs of nutrient deficiency, then switching to a fertilizer specific for palm trees is important.
Nitrogen is especially useful for palms, especially potted palms that have a great deal of green in proportion to the rest of the plant. This nutrient aids in the transfer of energy and is a part of chlorophyll, which is vital to the photosynthesis process. Signs of a nitrogen deficiency in palm trees include slower growth, as well as lighter green leaves than the palm normally would have.
While nitrogen is necessary, palms that suffer from lack of potassium are often more at risk for long-term problems. That is why choosing a palm tree fertilizer that has more of this nutrient is recommended. For palm tree owners using a general-use fertilizer, the potassium content may not be enough to truly help the tree. Yellowed to brown older fronds could signal a deficiency, which could take two years or more to completely correct, or could be fatal to the tree if not corrected. Choosing the right fertilizer will help prevent this situation.
Phosphorous, while also a vital component in photosynthesis, is typically not a big problem for palm trees. That is why most palm tree fertilizers do not have as much phosphorous as they do nitrogen and potassium. It is not good to totally deprive the tree of phosphorous, but the best fertilizer will focus on those other nutrients.
One of the other important ingredients in a good palm tree fertilizer is magnesium. In fact, if a gardener is trying to correct a potassium deficiency, then magnesium becomes even more important because as potassium is added, it can make a magnesium deficiency worse. A good fertilizer for palm trees will have 1 to 3% magnesium. While low amounts of this mineral is rarely fatal, it will make the palm look unhealthy.
Growers may also prefer choosing an organic fertilizer rather than a chemical one. This is a personal preference and typically makes no difference to the palm tree. No matter which fertilizer is used, choosing one that has a 2-1-2 or 2-1-3 ratio is the most important criterion.