Proper nutrition and pruning keep palms healthy
Palms are popular in Brevard, but non-native palms tend to suffer from nutritional deficiencies here in Florida because of our nutrient-poor sandy soils.
Many landscapes contain palms with fronds exhibiting various amounts of yellow, brown, and green tissue. On the other hand, a healthy palm will produce deep green fronds which turn brown only when they are being shed.
If you have palms in your landscape, here is information that will help you to keep them healthy.
Never use turf fertilizer within 50 feet of any palm
Your palms would be better off with no fertilizer than a turf fertilizer. That is because synthetic turf fertilizers should contain at least 50% slow-release nitrogen (to comply with the fertilizer ordinances that have been adopted throughout Brevard County sfyl.ifas.ufl.edu/brevard/lawn-and-garden/fertilizer-ordinances), but the potassium and magnesium sources are quick-release.
The slow-release nitrogen will continue to be released over a longer period, promoting new growth, but the potassium and magnesium will no longer be available, which could lead to deficiencies of one or both macronutrients.
Nutritional deficiencies are visible in palm fronds
New growth will display manganese and boron deficiencies and older fronds will exhibit potassium and magnesium deficiencies. The most common deficiency in palms is potassium, and the initial sign is translucent yellow spots that are evident when the frond is backlit by the sun.
As the deficiency becomes more severe, the older fronds will turn brown near the leaf tips. 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 if not corrected.
One exception to this rule is the Bismarck palms. A healthy Bismarck palm should have silver fronds that spread out 4 feet wide. Instead, many of the Bismarck palms I see have dull 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 if that is true.
Magnesium deficiencies also occur naturally here in Canary Island date palms, Phoenix canariensis, but are induced by improper fertilization in 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 frond, since it is supplying the new growth with the nutrient(s) that it can’t 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. For this reason, only remove fronds that are totally brown.
A lack of manganese 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 (at the base of the frond) will begin to exhibit symptoms first.
The most severe case of a manganese deficiency is called frizzle top because all the new fronds are brown and crinkled. Severe deficiencies of manganese can be fatal for palms and palm-like plants such as Sago palms.
Boron deficiencies also occur in the newest growth and are 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 doesn’t open properly. This deficiency, when severe, can also kill a palm.
Get a soil test
To discover if there are any nutritional deficiencies in the soil, send a soil sample to our UF/IFAS soil testing lab. Pay for the $10 test B so the phosphorus, potassium, magnesium, copper, manganese, and zinc levels are calculated. The soil testing form can be found at /edis.ifas.ufl.edu, search for “Soil Test Form.”
All palms (and plants, lawn, etc.) would also benefit from re-mineralizing the soil by applying a volcanic source of trace elements (i.e., Azomite, etc.) and/or kelp meal. The trace elements are important for palms that are native to volcanic islands, such as Canary Island Date palm and the Bismarck palm and the coconut palm.
Inoculate soil with beneficial bacteria and mycorrhizal fungi
The last recommendation, which to me is the most important one, is to inoculate the soil with beneficial bacteria and mycorrhizal fungi to get the biology around the root systems of palms. This is how nature grows plants, though the use of more than 2 pounds of a synthetic fertilizer, which are soluble salts, will kill the microbes.
Organic fertilizer can be used to supply nutrients while the soil food web is getting established, and once established, it will supply the palm with the nutrients needed.
There are products that contain a variety of soil microbes, so it is easy to get the soil food web established. For more information on this topic, email me at [email protected].
Don’t prune green or yellow palm fronds
All palms naturally shed fronds quickly. An old frond will go from green to yellow to brown in just three days. If all the fronds on your palms aren’t a solid green and healthy, they may have a nutritional deficiency or two.
This point bears repeating, when it comes to pruning palms, because the best policy is to only remove totally brown fronds. Also, do not attempt to pull off fronds, because that could wound the trunk. Never use climbing spikes on palm trunks, either. Spikes will also cause wounds that could be entry points for pathogens throughout the entire life of the palm.
Nutritional deficiencies, if they aren’t the primary cause of death, could be the root cause of insect pests (i.e., palmetto weevil, etc.) or diseases that can lead to death.
For more information, and to see photos of nutritional deficiency symptoms in palms, check out this link: edis.ifas.ufl.edu/topic_palm_nutrition. If you have palms in your landscape, go take a good look at their fronds and if you are in doubt, get the soil tested.
After all, totally green (or silver) palms not only look the best, but 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 [email protected].
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