Early "flecking" stage of potassium deficiency

This deficiency is very common in Florida where soils are naturally deficient in potassium and are quickly leached of this very soluble mineral element. In California, it is not a conspicuous problem. Symptoms vary among palm species, but always occur first on oldest leaves and affects progressively newer leaves as the deficiency becomes more severe. On many palms, the early symptoms are translucent yellow or orange flecks on the leaflets or segments, with or without necrotic spots. Areas of necrosis often can be seen along the margins. On some species, marginal necrosis is the typical first sign of deficiency. As the symptoms progress, the entire leaf appears burnt and withered. In date palms (Phoenix spp.) symptoms are slightly different in that older leaves show an orange-brown or dull yellow discoloration near the tip, in contrast to the bright yellow of magnesium deficiency. The leaflet tips, rather than the margins, become necrotic as the deficiency progresses. When all available potassium has been shunted from the older leaves to the new growth, the palm declines. `Pencil-pointing' (an abrupt reduction in trunk diameter) and the emergence of small, frizzled or chorotic new leaves indicate that without immediate treatment, the palm will probably die. Potassium deficiency affects most palms, but in Florida the most susceptible species are royal, queen, coconut, areca and spindle palms. Treatment requires soil applications of potassium sulfate at rates of 3 to 8 lbs per tree 4 times per year plus 1/3 to 1/2 as much magnesium sulfate to prevent a potassium-magnesium imbalance (and resulting magnesium deficiency) from occurring. Symptomatic leaves on K-deficient palms will never recover and must be replaced by new, healthy leaves. In severely deficient palms, this means replacing the entire canopy which may take 2 years or longer. Foliar sprays with K fertilizers are ineffective in correcting the problem since the amount of K supplied by a foliar spray is insignificant compared to the amount needed to correct the problem.

Later stages of potassium deficiency on Coconut (Cocos nucifera)

Potassium deficiency on Thatch Palm (Thrinax sp.)

Early potassium deficiency on pygmy date palm (Phoenix roebelenii)

An overall light green color and decreased vigor of the palm are indicative of N deficiency. It is usually only seen in the landscape on palms planted in infertile soils without supplementary fertilization. Application of any fertilizer containing nitrogen will quickly improve the color of the foliage.

Magnesium deficiency on Date Palm (Phoenix dactylifera)

Magnesium deficiency is very common in Florida, and anywhere else where palms are planted on poor, infertile soils. Date palms (Phoenix spp.) are particularly susceptible. Visible symptoms begin on the oldest leaves and progress upward to the younger foliage, typically a broad light yellow band along the margin of the older leaves with the center of the leaf remaining green. In severe cases, leaflet tips may become necrotic, but Mg deficiency is rarely if ever fatal to palms. Magnesium deficiency is best treated preventatively since treatment of deficient palms takes considerable time. As with K deficiency, symptomatic leaves will never recover and must be replaced by new healthy leaves. Applications of magnesium sulfate (epsom salts) at rates of 2 to 4 lbs per tree 4 times per year should correct the problem.

Magnesium deficiency on Date Palm (Phoenix dactylifera)

"Frizzetop" caused by manganese deficiency on Coconut (Cocos nucifera)

Manganese deficiency or `frizzletop’ is a common problem in palms growing in alkaline soils, because this element is relatively insoluble at high pH. Symptoms occur only on new leaves which emerge chlorotic, weak, reduced in size and with extensive necrotic streaking in the leaves. As the deficiency progresses, succeeding leaves will emerge completely withered, frizzled, or scorched in appearance and greatly reduced in size. Later, only necrotic petiole stubs will emerge and death of the bud quickly follows. In some palms such as coconut, which are not normally affected by the problem, cold soil temperatures during the winter and spring months reduce root activity and thus the uptake of micronutrients (especially Mn). Coconut palms severely deficient in Mn during the winter and spring will usually grow out of the problem without special treatment once soil temperatures warm up in late spring. Other palms such as queen, royal, paurotis and pygmy date palms, are highly susceptible to Mn deficiency and must be treated with soil or foliar applications of manganese sulfate or they will likely die.

Iron deficiency on Lady Palm (Rhapis excelsa)

Iron deficiency is relatively uncommon in landscape palms and is not usually caused by a lack of Fe in the soil, or even by high soil pH, as in many other plants. Iron deficiency usually appears on palms growing in poorly aerated soils or those that have been planted too deeply. Water-logged soils and deep planting effectively suffocate the roots. Symptoms appear first on the new leaves and in most palms consists of uniformly chlorotic new leaves, with green coloration entirely restricted to the veins of the new leaves. As the deficiency progresses, new leaves will show extensive dead tissue at the tips (necrosis) and reduced leaf size. Iron deficiency symptoms can sometimes be temporarily alleviated by regular foliar applications of iron sulfate or chelates, but long term correction will only occur when the poor soil aeration or improper planting depth that caused the deficiency is corrected. It is also important to remember that any injury to the root system can cause nutritional deficiencies to appear. Diagnosis of nutrient deficiencies by visual symptoms alone can be difficult, since some of the symptoms overlap considerably in some species. For instance, Mn and late-stage K deficiencies are easily confused on queen and royal palms. Potassium and Mg deficiencies are very similar in pygmy date palms and K and Fe deficiencies can be very similar in royal palms. If complex symptoms defy a simple diagnosis, it is wise to have a diagnostic laboratory perform a leaf nutrient analysis before undertaking any corrective action.

Palms suffer quickly and conspicuously from improper mineral nutrition, whether due to insufficient or incorrect fertilization. They also may exhibit certain nutritional disorders in unique ways compared to other ornamental plants. Some nutritional problems in palms are difficult to diagnose accurately because symptoms of several different mineral deficiencies may overlap. The following are the most common nutritional deficiencies likely to be encountered in the landscape.