Here's how to care for the palms in your Florida landscape | Sally Scalera
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Palms are popular ornamental plants, but sadly, non-native palms tend to suffer from nutritional deficiencies in Florida due to our sandy soils that often lack nutrients.
Many landscapes contain palms with fronds exhibiting various amounts of yellow, brown, and green tissue. On the other hand, healthy palms produce deep green fronds and only produce brown fronds over a three-day period when they are being shed.
If you have palms in your landscape, here is information that will help you keep them healthy.
Never use synthetic turf fertilizer within 50 feet of any palm. Your palms would be better off with no fertilizer than a typical turf fertilizer. That is because turf fertilizers should contain a minimum of 50% slow-release nitrogen, (to comply with the Brevard County Fertilizer Ordinance), but the potassium and magnesium sources are quick-release.
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The 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, since the nitrogen is released over a longer period.
Nutritional deficiencies are 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, and the initial sign is translucent yellow spots visible when the frond is backlit by the sun. As the deficiency becomes more severe, the older fronds will develop brown leaf tips near the end of the frond.
The leaf petiole, which runs down the center of the frond, will be the last part to become necrotic.
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 silver fronds that spread out four feet wide. Instead, many of the Bismarck palms I see have off colored older fronds that are folded and drooping. 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 in Florida in Canary Island date palms, Phoenix canariensis, but are induced by improper fertilization on most other palms. The yellow tissue produced by a magnesium deficiency will be found on the older fronds also. It is possible, and not uncommon, to find palms experiencing both magnesium and potassium deficiencies, especially in Canary Island date palms.
When potassium and/or magnesium deficiencies are present, do not remove the symptomatic frond, since it is supplying the new growth with the nutrients that it cannot obtain from the soil.
The removal of partially green, older fronds will just push the nutritional deficiency up into the new growth. This could eventually lead to the death of the palm. Only remove fronds that are totally brown.
Manganese, when lacking, will show up in the newest fronds. At the beginning, there will be interveinal chlorosis (yellowing) and necrosis (death of the tissue). The leaflets nearest the trunk will begin to exhibit symptoms first.
The most severe case of a manganese deficiency is called frizzle top, because all the new fronds will be brown and crinkled. Severe deficiencies of manganese can be fatal for palms and palm-like plants such as Sago palms.
Boron deficiency also occurs in the newest growth and is evident by the puckering or deformity of the new growth. This deficiency can also be the cause of multiple heads being produced on a palm trunk.
Other symptoms include kinked and drooping new leaves, or the spear leaf not opening normally. This deficiency can also kill the palm.
If you are concerned about your palms, 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, and zinc are calculated. The soil testing form can be found at edis.ifas.ufl.edu. Search for "Soil Test Form.
It would also be beneficial to re-mineralize your soil by applying a volcanic source of trace elements (i.e., Azomite, etc.) This product is good for all plants, including the grass.
Inoculating the soil surrounding the palm with beneficial microbes such as mycorrhizal fungi and bacteria can help, too. There are products that contain a variety of soil microorganisms, which is good because a diverse population of microbes will help all perennial plants grow better. For more information on this topic email me at sasc@ufl.edu.
All palms naturally shed fronds quickly. An old frond will go from green to yellow to brown in just three days. 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.
When it comes to pruning palms, the best policy is to only remove totally brown fronds. Do not attempt to pull off fronds that will not come off easily, as that could wound the trunk, and never use climbing spikes on palm trunks for any reason. Spikes cause wounds that could be entry points for pathogens throughout the life of the palm.
Nutritional deficiencies, if they aren’t the primary cause of death, could be the root cause of pests or diseases that lead to death.
For more information, visit edis.ifas.ufl.edu/topic_palm_nutrition. This page has numerous links to bulletins, many of which include photos.
If you have palms in your landscape, go take a good look at their foliage, and if you are in doubt, get the soil tested. After all, green palms not only look the best, they are also the healthiest.
Sally Scalera is an urban horticulture agent and master gardener coordinator for the University of Florida’s Institute of Food and Agriculture Sciences. Email sasc@ufl.edu.
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This article originally appeared on Florida Today: Non-native palms in Florida can face multiple nutritional deficiencies
