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Fairchild’s tropical garden column: Fine-tuning your palm fertilizer

Foxtail palms are notoriously nutrient deficient. Premature trimming of green leaves can exacerbate the deficiency.
Foxtail palms are notoriously nutrient deficient. Premature trimming of green leaves can exacerbate the deficiency. Fairchild Tropical Botanic Garden

Palms are beautiful ornamentals and are well used because of their gorgeous, dark green leaves. Nothing exudes tropical paradise quite like a dark green canopy of folded leaves atop a solitary trunk. However, our tropical beauties are often plighted by nutrient deficiencies and don’t look quite as green as we’d hope.

Are we simply setting our expectations too high or do we need to work harder to help our palms? With palms, the answer is almost always to work harder.

Palms are relatively simple plants. Their closest relatives are the grasses, an indicator of their simple growth habit and requirements as well. For a frustrating palm problem the answer is usually equally irritating — fertilizer. Since palms are slow growing, it often takes years to completely overcome a deficiency.

Here is my step-by-step guide to creating a palm-fertilizing schedule to properly feed your palms and combat those discolored leaves.

Different palm species have different nutrient requirements. Certain palms are hardy, like sabal and thatch palms; others are always nutrient deficient, such as date and foxtail palms.

▪ Get your palm on a regular fertilizer routine immediately. This is similar to going to the dentist for a routine cleaning. Even though nothing appears to be wrong with your teeth, it is important to clean up that plaque. I recommend a 180-day 13-3-13 fertilizer, full of micronutrients. Spread the fertilizer twice a year: once at the beginning of the rainy season in May and again at the end of the rainy season in October. If you have a Florida native, like a sabal palm or thatch palm, this will probably be enough to keep it happy year round.

▪ If after a year of this basic regime your palm still has nutrient deficiencies, it’s most likely a potassium or magnesium deficiency and the lower leaves of the palm canopy get discolored. I would suggest a using foliar spray fertilizer, which delivers the nutrients directly to the palm. Not every palm requires this, only the ones that are deficient. Apply foliar spray every two to four months depending on the severity of the problem (and your budget). Spray evenly on all leaves, on all sides of the leaves. Do not spray during daylight or your palm will get severely burned. Spray before/at sunrise or at/after sunset.

Potassium deficiencies may be unsightly but they are not fatal. Your treatment of the deficiency can be more detrimental than the deficiency. A burn can be very devastating for the palm and a bad trim can be damaging as well. Don’t trim the deficient leaves. The deficiency is in the bud of the palm, where the new leaves are being produced. If the bud doesn’t have enough nutrients, it will take nutrients from the older leaves. By removing the discolored leaves, you are taking away needed nutrients.

▪ The last step is fine-tuning your fertilizing schedule. After a year of foliar spray, try and take some palms off the more intense fertilizing routine. It is possible that they don’t need all the extra fertilizer now that they are healthy.

You are a palm gardener now and after two years you should know the requirements of your individual palms. Different palm species have different nutrient requirements. Certain palms are hardy, like sabal and thatch palms; others are always nutrient deficient, such as date and foxtail palms. Sometimes, even the same species will have different requirements because of planting locations. An individual planted in full sun may have different fertilizer requirements than the same species planted in part shade.

It would be easy to fertilize all your palms with the same fertilizer at the same frequency. However, in order to get that lush green tropical look, palms require a little more work. Take the time to get to know your palms and fine-tune their fertilizing schedule. Even though the palms can’t thank you for it, the envious looks from your neighbors will be reward enough.

Sara Edelman is the palm and cycad manager at Fairchild Tropical Botanic Garden.

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