Palm nutrient deficiencies and why yellow fronds are left on: what UF/IFAS and Clemson describe

This page describes what the named extension services say. It does not diagnose a palm or tell anyone how much of any fertilizer to apply. Pruning rules for palms are on the palm pruning page.

Which leaves show which deficiency

Timothy K. Broschat of UF/IFAS writes that deficiencies of nitrogen, potassium, magnesium, iron, manganese and boron are common on palms in all Florida soil types. The publication places each one on a different part of the crown.

Nutrient	Where symptoms show first	What UF/IFAS describes
Nitrogen	Oldest leaves	A uniform light green colour. Over time the whole canopy except the spear leaf turns chlorotic, growth slows sharply and trunks taper.
Potassium	Oldest leaves	Yellowish translucent spotting in some species and marginal or tip necrosis in others, often with withered and frizzled leaflets. Called the most common nutritional disorder of palms in the world.
Magnesium	Oldest leaves	Broad yellow bands along the leaf margins while the centre stays distinctly green.
Manganese	Newest leaves	New leaves emerge chlorotic with necrotic streaks, then withered and curled, a pattern called frizzletop.
Iron	Newest leaves	Uniform or interveinal yellowing of new leaves while older leaves stay green. In severe cases the growing bud can die.
Boron	Developing leaves and spear	Sharply bent leaflet tips called hookleaf, and spear leaves that fail to open normally.

What the sources say about causes

UF/IFAS says nitrogen deficiency is uncommon on palms in native Florida soils but common on palms transplanted from containers into the ground. It says iron deficiency in palms is usually not caused by a lack of iron in the soil but by factors that reduce root respiration, and it names poor soil aeration and planting too deeply among them. Clemson Extension (HGIC 1019, revised December 1, 2007) says planting a palm deeper than it was grown can lead to root suffocation, nutritional deficiencies and root rot, and that decline may take several years to show.

Clemson says palms are very susceptible to deficiencies of nitrogen, potassium, magnesium and manganese, especially in sandy regions such as the outer Coastal Plain. It adds that palm roots can extend 30 to 50 feet or more from the trunk and take up fertilizer applied to nearby turfgrass. Turfgrass fertilizers typically have high nitrogen to potassium ratios and little magnesium, and Clemson says the extra nitrogen can dilute potassium in the palm and make a potassium deficiency worse.

Diagnosis, as the sources describe it

UF/IFAS says most palm deficiencies can be diagnosed from visual symptoms, and that leaf analysis can help confirm a diagnosis. Iron and boron are the exceptions, because symptoms correlate poorly with leaf concentrations of those two. The publication gives the sampling method as 4 to 6 central leaflets from the youngest fully expanded leaf. It says soil analysis is not particularly useful, because palm symptoms often bear little resemblance to soil nutrient profiles and no optimum soil levels have been established for any palm species.

Why yellow and brown fronds are left on

UF/IFAS Gardening Solutions says half-dead or yellow fronds may result from nutrient deficiencies, that removing them early can reduce the green canopy and erase evidence of symptoms, and that such fronds often provide some nutrients. It notes that some palms, areca among them, naturally yellow their older fronds without a nutrient problem. Clemson makes the same point more strongly: removing unattractive lower leaves of palms deficient in potassium and magnesium moves the potassium symptoms up to the next tier of leaves. Its pruning guidance is to take only completely dead and loose leaves, badly damaged or diseased leaves, fruit and flower stalks, and it says a leaf with a green petiole is not dead. The Broschat paper cited by UF/IFAS (HortScience, 1994) is titled "Removing potassium deficient leaves accelerates rate of decline in pygmy date palms."

Where fertilizer recommendations are printed

UF/IFAS directs readers to a separate publication (ENH1009) for Florida fertilization recommendations.