Technically panhandle Florida is on the borderline of the sub-tropics by virtue of its latitudinal location. It is roughly halfway between the tropical zone and the northern temperate zone, getting, by most estimates, the best of both worlds.
There are winters here and they are usually pretty mild, at least by Minnesota standards. A light dusting of snow every 30 years is manageable.
Local summers can be “pretty warm” and humid but are not usually the beastly baking which necessitates a siesta or nap in the middle of the day. With this balmy location, the plant population is a mix of heat tolerant temperate plants and tropical foliage which handles the occasional freeze.
Successfully growing palms in Florida landscapes is subject to effectively overcoming a number of potentially serious nutrient deficiencies. Prevention and treatment of these deficiencies are dependent upon early and accurate diagnoses of the missing elements.
One of the most notable in the latter category are palms. These plants are a popular landscape addition adding a striking contrast to the more traditional shrubs and annuals.
Palms make an attractive addition to most north Florida home landscapes, but just like many other plants they have a need for supplemental nutrients to reach their peak performance.
It is important to remember nutrient deficiencies are more easily prevented than corrected after they become visually evident. Correction of nutrient deficiencies can take as long as three years for some elements.
Many of Florida’s soils have very low capacities to retain nutrients in the palm’s root zone during periods of heavy rainfall or irrigation. The only effective way to keep these elements readily available to plants during the interval between fertilizer applications is to use slow-release sources.
If 100 percent of the nitrogen, phosphate and potassium are slow-release, that greatly reduces the potential for environmental damage from run-off and the need to frequently apply these important elements.
Ideally, most micronutrients need to be in a water-soluble form unlike the aforementioned macronutrients which should be in slow-release form. However, the granular, slow-release forms of boron are safer and more effective for Florida landscape soils.
Epsom salt is a water-soluble form of magnesium sulfate, an important micronutrient for palms. Look for the term “prilled kieserite” on the tag of fertilizers blended specifically for palms. It is a more slowly soluble form of magnesium sulfate which is both effective and low-cost.
Treatment of severely Mg-deficient palms can require a year or more and is accomplished by broadcasting a controlled-release magnesium source, such as prilled kieserite, at rates of two to five pounds per tree to the area under the canopy four to six times annually.
How the fertilizer is applied will determine whether the application will deliver the desired results. Concentrating fertilizer in holes, as spikes, or in bands around the trunks of palms is less effective than spreading the same amount of fertilizer uniformly throughout the root zone under the canopy.
Nutrient movement in the soil is almost exclusively downward in direction. Only the small proportion of the palm’s root system directly under concentrated fertilizer will ever be contacted if applied in that manner.
Additionally, a concentration of fertilizer is more likely to burn palm roots than fertilizer distributed over a larger area. The sometimes-encountered practice of injecting water-soluble fertilizers into the “root zone” of palms is never recommended.
Quarterly fertilizer application can be suspended during the colder parts of the year. Even the cold hardy palms will minimize their need for supplemental nutrition.
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