Protect your palm trees with a little TLC and these tips | Sally Scalera

Palms are popular ornamental plants, and many new species are grown throughout the county. Our native palms (i.e., Sabal/Cabbage, Everglades, etc.) can handle our poor soil much better than non-native palms. Have you noticed many of the palms don’t have solid green fronds? Often, there are yellow and/or brown areas on some or many of the fronds.

As you walk or drive around, notice the palms you pass by to see if every frond is a deep green for its entire length. The palms that are a deep green throughout the entire canopy surprise me the most because they are so rare. Many landscapes contain palms with fronds exhibiting various amounts of yellow, brown, and green tissue. A palm will only produce a yellow or brown frond when it is shedding it. It is easy to see in self-cleaning palms (i.e., Royal, Foxtail, Christmas, etc.) that in a three-day period, the frond will go from green (hopefully) to yellow and/or brown, and then the frond will fall off.

If you have palms in your landscape, here is information to help you keep them healthy.

Don’t use synthetic turf fertilizer within 50’ of any palm, and don’t apply any fertilizer that contains nitrogen or phosphorus until Oct. 1, when the Brevard County fertilizer ordinance is no longer in effect. Your palms would be better off with no fertilizer than a typical turf fertilizer. This is because turf fertilizers should contain a minimum of 50% quick-release nitrogen, but all of the potassium and magnesium sources are quick-release. Therefore, the remaining slow-release nitrogen, which promotes new growth, can induce a potassium and/or magnesium deficiency if the potassium and/or magnesium are no longer available.

Signs of nutritional deficiencies will be evident in the fronds. New growth will display manganese and boron deficiencies, and the older fronds will show potassium and magnesium deficiencies.  The most common deficiency in palms is potassium. The older fronds will develop brown leaf tips, and as the deficiency becomes more severe the entire frond can turn brown.

Potassium deficiency symptoms will vary between palm species, but they will all produce dead or brown tissue, which could be fatal. One exception to this rule is Bismarck palms. A healthy Bismarck palm should have four-feet-wide silver fronds. Instead, I see many Bismarck palms with drooping, off-colored older fronds. I suspect the cause is a potassium deficiency, but a soil test would be needed to confirm that is the case.

Magnesium deficiencies occur naturally here in Florida in Canary Island date palms, Phoenix canariensis, but can also be induced by improper fertilization on most other palms. The yellow tissue produced by magnesium deficiency will surround a green triangle of tissue in older fronds. It is possible, and not uncommon, to find palms experiencing both magnesium and potassium deficiencies, especially in Canary Island date palms.

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When potassium and/or magnesium deficiencies are present, do not remove the symptomatic frond since it supplies the new growth with the nutrient(s) it cannot obtain from the soil. Removing partially green, older fronds will push the nutritional deficiency into the new growth. This could eventually lead to the death of the palm. For this reason, only remove totally brown fronds.

A manganese deficiency will show up in the newest fronds. Interveinal chlorosis (yellowing) and necrosis (tissue death) will occur at the beginning. The leaflets nearest the trunk will begin to exhibit symptoms first. Severe manganese deficiencies can be fatal for palms and palm-like plants such as Sago palms. This symptom is often called “frizzle top” because the newest fronds emerge brown and deformed.

Boron deficiencies will also occur in the newest growth and are evident by the puckering or deformity of the new growth. This deficiency can also cause multiple heads to be produced or new growth to grow at a 90° angle. Other symptoms include kinking and drooping new fronds or the spear leaf not opening correctly. This deficiency can also kill the palm.

Most palms naturally shed fronds quickly, though Cabbage/Sabal palms tend to hold onto them until a windy storm blows them off. If there are yellowish (magnesium deficiency) or brownish (potassium deficiency) fronds remaining on a palm for more than three days, that is a sure sign that the palm has a nutritional deficiency.

Another way to protect your palms from future nutritional deficiencies is to cut off the flower stalk after the flowers fade. One caveat: If you use a systemic insecticide (i.e., Imidacloprid, etc.) around the palm, remove the flower stalk before it blooms to protect the bees. Allowing the seeds/fruit to be produced will require nutrients, which could cause future nutritional deficiencies for the palm.

If you are concerned about your palm(s), send a soil sample to the UF/IFAS soil testing lab. Pay for the $10 test B so the levels of phosphorus, potassium, magnesium, copper, manganese, zinc, and boron levels are calculated. The soil testing form can be found at https://edis.ifas.ufl.edu/pdffiles/SS/SS18700.pdf. It would also be beneficial to re-mineralize your soil, especially for non-native species, by applying a volcanic source of trace elements (i.e., Azomite, etc.)  This product is good for all plants, including turf and edible plants for more nutritious food.

To help your palms grow healthy, with less effort from you, consider improving the soil health throughout your yard (which will benefit all your plants). Healthy soil is needed to produce healthy plants and protect water quality. For more information on this topic, email the UF/IFAS Extension Brevard County Master Gardeners at [email protected].

Nutritional deficiencies, if they aren’t the primary cause of death, could be the root cause of insect pest infestations or diseases that lead to death. After all, green palms not only look the best, but they are also the healthiest. A green frond should only be pruned off if it touches a building because it can allow insects and other creatures to enter the structure. If you have palms in your landscape, go take a good look at their foliage. If all the fronds are a deep green, all is good, so leave those fronds alone!

Sally Scalera is an urban horticulture agent and master gardener coordinator for the University of Florida’s Institute of Food and Agriculture Science.

This article originally appeared on Florida Today: Those palm trees you love can use a little TLC | Sally Scalera