Palm Trees frequently suffer from improper mineral nutrition in the landscape. Some of the nutritional deficiencies of palm trees are nitrogen (N), potassium (K), magnesium (Mg) and manganese (Mn).
Other essential nutrients such as boron (B), calcium (Ca), copper (Cu) and zinc (Zn) are occasionally found to be deficient if they are not present in the fertilizers applied, but these deficiencies are not very common in the landscape.
Nutrient deficiencies can be caused by insufficient nutrients in the soil, a nutrient imbalance, poor soil aeration, a high soil pH and an excessive planting depth.
1. Palm Tree Maganese Deficiency
Manganese deficiency can be fatal to palm trees. This is a common problem in high pH soils (above pH 6.5) because manganese is insoluble at high pH levels. Additional causes can be high water tables or poor drainage, and excessive amounts of soil phosphorus, as it will tie up certain micronutrients, particularly manganese.
Early symptoms of manganese deficiency are yellowing between the veins accompanied by interveinal necrotic streaking on the newest leaves. If the deficiency is advanced, leaves emerge completely frizzled, withered, scorched and reduced in size.
Prevention and Treatment of Manganese Deficiency
Have a soil test performed to determine the soil pH and if necessary, adjust downward to increase the availability of manganese. Manganese sulfate applications to the soil or foliage can be used to avoid the problem. Apply 1 teaspoon manganese sulfate per gallon water to soil around the palm two or three times per year.
2. Palm Tree Magnesium Deficiency
Magnesium deficiency is never fatal and is primarily a cosmetic problem in landscape palms. Classic symptoms are marginal chlorosis on the oldest leaves which progress upward to younger foliage.
Magnesium deficiency in Palm Trees is distinguished by a typically broad lemon-yellow band along the margin of older leaves with a green center and a distinct boundary between the yellow and green portions.
If leaflet tips are also necrotic (brown dead tissue), this indicates the presence of potassium deficiency on the same leaves. As with potassium deficiency, leaves with a magnesium deficiency will not recover, and must be replaced by new healthy foliage.
Prevention and Treatment of Magnesium Deficiency
Coated or uncoated “prilled” (pelletized) kieserite can be applied to prevent or correct magnesium deficiency, but may be difficult to find. Epsom salts (magnesium sulfate) is very water soluble, and tends to leach from sandy soils very quickly.
However, the use of 2 to 4 pounds of magnesium sulfate per tree along with controlled-release potassium four times per year should prevent further symptoms from occurring. If the soil pH is low, adjust using dolomitic limestone based on soil test results.
Avoid the use of magnesium oxide as a treatment if the soil has a neutral or alkaline pH, as it is quite insoluble in soils with a high pH.
3. Palm Tree Potassium Deficiency
Palm Trees need potassium in large amounts. Potassium deficiency is perhaps the most widespread and serious of all disorders of palms. Usually you potassium affects older leaves on the palm tree and than progresses to the newer leaves as the problem becomes more severe. You will notice translucent yellow to orange spots. There also can be black or necrotic spotting.
Leaflets will usually have areas of necrosis (dead tissue) along their margins and tips. Symptoms are worse at leaf tips and margins and less severe at the base of the leaves. As symptoms progress, tips of leaves will appear withered, burnt and frizzled. The midrib typically stays greenish-yellow for a period of time.
Potassium deficiency result can be fatal to the palm tree. Potassium tends to leach rapidly from sandy soils, and it is in these soils that potassium deficiency is more apt to occur. In heavier clay soils, the rate of potassium leaching is reduced.
Deficiencies in clay soils may be more due to insufficient potassium fertilizer applied. Palm trees that are in lawns may become potassium deficient as many turf grass fertilizers are high in nitrogen, but low in potassium. Palm trees need fertilizers that contain potassium as high as or higher than the nitrogen content. Fertilize all palm trees separately from the lawn.
Prevention and Treatment of potassium deficiency
Potassium deficiency can be prevented and/or treated with applications of sulfur-coated (slow-release) potassium sulfate, but slow-release magnesium should also be applied simultaneously to prevent potassium to magnesium imbalance.
If treated, necrotic leaves will not recover, but new growth should become healthy and will eventually replace the injured leaves.
4. Palm Tree Boron Deficiency
Boron deficiency in palm trees can cause leaves to appear small and crumpled. Other symptoms are sharp bends in the trunk with horizontal growth and bud necrosis or death.
Prevention and Treatment of Boron Deficiency
Boron can also be toxic even in small amounts, so generally fertilizers for palms should contain only very small amounts of boron. Sodium borates, boric acid, borax or Solubar can be applied at 2 to 4 ounces per tree.
5. Palm Tree Nitrogen Deficiency
Nitrogen deficiency is not a major problem in landscape palm trees unless soils are nitrogen-poor. Most palm trees generally require low levels of Nitrogen, especially in comparison to turfgrass. Symptoms of nitrogen deficiency are uniform light green color foliage and a decrease in growth.
Nitrogen deficiencies are more common on light or sandy soils. This is the nutrient deficiency that is most common in container-grown palms, whereas potassium, manganese and magnesium deficiencies are more pevalent in landscape situations.
Prevention and Treatment of Nitrogen Deficiency
Treatment with any fertilizer containing N will quickly improve leaf color. The fertilizer nitrogen should be in a slow-release form.
6. Palm Tree Iron Deficiency
Iron deficiency in palm trees is primarily a cosmetic problem. Palm trees usually survive, but will exhibit green veins surrounded by yellow tissue, and this is usually seen on newest leaves first.
As the iron deficiency becomes more severe, new leaves will show extensive tip necrosis, and there will be a reduction in leaf size. Iron deficiency in palm trees is usually induced in palms growing on poorly aerated soils (compacted or over-watered) or in palms planted too deeply.
Iron deficiency may occur in palms with a damaged or inadequate root system which leaves the plant unable to take up sufficient nutrients from the soil. This deficiency is much less often caused by a lack of iron in the soil, or by high pH soils.
Prevention and Treatment of Iron Deficiency
In alkaline soils, iron-deficient palms can be treated with chelated iron fertilizers. In some cases, iron deficiency symptoms can be temporarily alleviated by regular foliar applications of chelated iron or iron sulfate, but long term corrections will only occur when the poor soil aeration or proper planting depth is corrected.
The rate of iron sulfate to use for foliar application is ½ teaspoon per gallon of water. Spray the foliage to runoff.