Palm Nutrition and Fertilization

Close look at a palm frond, the fronds have distinct yellow marks up and down the frond that you can see light coming through. — Potassium deficiency symptoms on older leaf of a coconut palm, showing translucent yellow-orange spotting. T. K. Broschat, UF/IFAS

Most people picture palm trees and sandy beaches when they book a trip to the Sunshine State. Palms are quite prized in Florida, waving on our state flag and proudly lining the streets of towns and cities. But these crowning jewels often suffer from nutrient deficiencies that can be detrimental to the plant.

It’s important to note that these deficiencies are much more easily prevented than corrected. The pH of the soil can impact nutrient uptake and is species specific. Improper fertilization, over-pruning or inadequate amounts of nutrients in the soil can all play a role in nutrient deficiencies.

As such, proper pruning and fertilization are your best methods for keeping palms healthy. A soil test prior to planting can help you determine the site conditions. But if your plant does begin to exhibit signs of distress, it’s good to be able to recognize the symptoms of the common nutrient deficiencies of palms.

Nutrient Deficiency

Potassium (K) deficiency is the most common nutritional disorder of palms. It is generally caused by insufficient levels in the soil which can be worsened when fertilizer high in nitrogen is used. Over-pruning can also lead to potassium deficiency. Early symptoms vary between species of palms but always appear first on the older leaves. This can include yellow spotting on the leaves or dead plant tissue in the form of brown leaf tips (necrosis). In severe cases, the entire canopy can have chlorotic, stunted, frizzled (crinkled/curled) leaves.

A circular palm frond with each leaf mostly yellow with a little green in the center of individual leaves. — Magnesium-deficient older leaf of palm showing yellow borders around leaflets. Photo: T. K. Broschat, UF/IFAS

Nitrogen (N) deficiency is uncommon in palms growing in Florida soil, but can be an issue in container palms newly transplanted into the ground. Signs include light green coloration in the oldest leaves that eventually become chlorotic (lacking in chlorophyll) and turn yellow.

Magnesium (Mg) deficiency is mainly a result of improper fertilization. The exception is Canary Island date palm (Phoenix canariensis), which is the only palm that commonly has chronic issues getting enough magnesium from the soil. Symptoms of magnesium deficiency can be chlorotic, highlighter-colored yellowing along the margins of the older leaves.

A young planted palm with fronds drooping and center growth stunted and twisted. — Manganese deficiency on palm caused by composted sewage sludge in the backfill.
Photo: T. K. Broschat, UF/IFAS

Manganese (Mn) deficiency can affect many different kinds of palms. Insufficient manganese in the soil is generally the cause. Sewage sludge and manure products are known to bind with manganese in the soil and reduce availability for the palm. Cold temperatures can also temporarily cause deficiency of this nutrient. Symptoms of deficiency include chlorotic new leaves with streaks of dead leaf tissue; some appear frizzled. The symptoms manifest in the new top growth and are more severe at the base of the leaf.

Iron (Fe) deficiency is not as common in palms as it is in other plants. It is usually not caused by lack of iron in the soil, but rather factors that reduce the roots’ ability to uptake iron. Poor soil aeration (compacted soil), planting palms too deeply, and injury from root rot can all cause iron deficiency. The symptoms include uniform chlorotic yellowing of the newest leaves, and in severe cases, new leaflets may have necrotic tips and stunted growth.

A palm tree with its upper trunk bent and growing sideways. — Christmas palm with boron deficiency showing trunk bending. Photo: T. K. Broschat, UF/IFAS

Chronic boron (B) deficiency is believed to be caused by soil drying and high soil pH. Heavy rains can lead to temporary deficiency. Boron deficiency can be hard to diagnose; symptoms come in many shapes and forms across different species and even vary within the same species. Symptoms generally begin in the top, new growth and include sharply bent leaf tips, necrosis and failure of newly emerging leaves to open. The leaves can also appear crumpled. The strangest symptom is the entire crown of the tree growing sideways, bent in one direction.

Management

First, if you are selecting a palm for the landscape, test the soil to ensure you choose the right palm for the right place. Some palms will have chronic nutrient deficiencies in high pH soils, while other species can manage just fine. Consult the online Florida-Friendly Landscaping™ Plant Guide for guidance.

Screen shot of the mobile FFL plant app — The FFL Plant Guide.

Also from Florida-Friendly Landscaping™ (FFL) are nine principles for successful, sustainable home gardening. One such principle is “Fertilize Appropriately.” Make sure to follow fertilizer directions recommended for your plant in order to reduce time spent on maintenance, increase the health of the plant and prevent excessive runoff into waterways.

For preventative measures (if the palm needs supplemental nutrition) use fertilizer labelled as 8-2-12+4Mg, or 8-0-12 +4Mg. The numbers represent the percentage of nitrogen, phosphorus, potassium and magnesium in the fertilizer. This combination of nutrients is suitable for all palms anywhere in Florida, but keep in mind that Florida native palms usually do not need added fertilizer. If using granular fertilizer, you should use a product with slow-release macronutrients and soluble quick-release micronutrients.

Never concentrate the fertilizer in specific areas; instead, apply evenly under the canopy around the entire root zone of the palm, which can be up to 50 feet in diameter. You can even apply the palm fertilizer to the whole landscape, including turfgrass. This prevents other fertilizers that are unsuitable for palms from leaching into the palm roots and causing more issues. For example, high-nitrogen fertilizers applied to turfgrass even 30 feet away from a palm have been known to compromise the palm by triggering potassium deficiency.

Screen shot of fertilizer ordinance map on mobile device — FFL also has an app to keep track of fertilizer ordinance.

Apply your palm fertilizer three times a year from spring through fall. Winter application is not necessary as plant growth slows down and nutrients are not needed during that time. And although tempting, don’t prune off yellowed fronds — they can be an indication of potential nutrient deficiency. Pruning can cause premature stress and damage the palm. Be patient, because correcting nutrient deficiencies can take anywhere from six months to two or three years.

It’s important to stay aware of your local fertilizer ordinances and any restrictive periods called “black-outs,” when the application of nitrogen and phosphorus in the landscape is forbidden. This is often during the summertime (June through September) in rainy months, when excess nutrients get washed into waterways and cause problematic algae blooms.

Most palms can be diagnosed with visual symptoms, but in many cases, leaf analysis can help. If you notice your palm showing signs of distress, send pictures of the entire palm as well as close-up photos of the leaves to your local UF/IFAS Extension office. Make sure to provide as much information about the site and its history as possible.