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Deficiencies

Nutrient deficiencies cause chronic disease in plants. When nutrients are lacking, important molecules like chlorophyll, DNA, RNA, proteins, and lipids cannot be manufactured. Enzymes may not carry out important chemical transformat*ions. In general, plant growth is slowed, and susceptibility to disease may increase. Flowering potted plants may be dwarfed, develop chlorosis or necrosis, have fewer flowers, and otherwise be unattractive.

Fig. 2. Typical symptoms of fertilizer deficiency in an unfertilized Aphelandra squarrosa. From the Compendium of Ornamental Foliage Plant Diseases.

Nitrogen is easily leached and must be supplied to plants frequently to prevent deficiency. A general chlorosis of the entire surface of older leaves, progressing upwards, is the most common symptom of nitrogen deficiency. Leaves may be reduced in size, internodes are shortened, and eventually a general loss of vigor or growth occurs (Fig. 2).
Phosphorus. One of the first symptoms of phosphorus deficiency is the production of small leaves and shortened internodes. Older leaves may lose their shine and become dull and eventually chlorotic. Green pigments are lost, so that red, yellow, and blue pigments show through, especially near main veins on the underside of leaves.
Potassium. Leaf and stem size are often reduced in plants that are deficient in potassium. The foliage remains its normal color on some plants; on others, necrosis and chlorosis occur, developing first on older leaves (Fig. 3).

Fig. 3. Older leaf of potassium-deficient Dictyosperma album. From Diseases and Disorders of Ornamental Palms.

Magnesium. A general reduction in plant vigor and reduced leaf size are common symptoms of magnesium deficiency. Interveinal and marginal chlorosis and necrosis also occur, developing first on older leaves (Fig. 4). On Philodendron scandens C. Koch & H. Sello subsp. oxycardium (Schott) Bunt. (heart-leaf philodendron), chlorosis occurs in a marginal V-shaped pattern. On some palms, only the tip becomes chlorotic. The chlorosis is a bronze color, and veins remain dark green. Premature senescence of older leaves may occur in mild cases.

Fig. 4. Magnesium deficiency on Phoenix. (Click image for expanded view).

Calcium deficiency is not common in foliage or flowering plants. Small yellow lesions form on the basal half of older leaves of calcium-deficient plants. Water-soaked spots often develop within the chlorotic areas. Symptoms progress into younger leaves, and the chlorotic spots become necrotic, so that leaves sometimes abscise prematurely. Color breaks occur on spathe tissue of calcium-deficient Anthurium andraeanum Linden (Andrae’s flamingo flower). Internodes of Ficus benjamina L. (weeping fig) become elongated and weak, and its leaves become chlorotic and stunted. Some cultivars of poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch), such as Gutbier V-14 Glory and Celebrate II, develop bract necrosis when foliar tissue calcium levels are low, a condition that is difficult to distinguish from bract necrosis caused by Botrytis.

Fig. 5. New leaf of iron-deficient Caryota mitis. (Click image for expanded view).

Iron can become deficient under interiorscape conditions and when the pH of the growing medium is above 7. However, the occurrence of iron defi*ciency is largely dependent on the specific requirements of the plant. Chlorosis of the youngest leaves, often with the veins remaining green, is the most common symptom of iron deficiency (Fig. 5). Yellowing, stunting, and abscission of new leaves can also occur. Soil pH can influence the availability of iron to plants and should be monitored periodically. The ability of roots to absorb iron is reduced by poor root health caused by inadequate soil aeration resulting from excess soil water.
Sulfur deficiency is rare under normal conditions of plant production. An overall chlorosis of new leaves occurs. This symptom is easily confused with the chlorosis caused by nitrogen deficiency in some plants.
Manganese deficiency occurs in some plants such as large palms with deformation and chlorosis of newly emerging leaves as the most obvious symptom. Plants that completely lack manganese can be severely stunted.
Boron deficient plants have shortened internodes, thickened stems, and reduced leaf size. New leaves of deficient Ficus elastica Roxb. Ex Hornem. (India-rubber tree) are stunted and deformed and become brittle and stiff. Terminal leaves are especially distorted.
Copper deficiency causes severe distortion and stunting of new growth. One of the most common examples of this deficiency occurs in Aglaonema commutatum Schott ‘Fransher.’ It’s leaves are distorted and dwarfed and sometimes have a hooked appearance, with the edges rolled upward toward the center (Fig. 6). Terminal buds die, and laterals sometimes initiate growth, forming a witches’-broom.

Fig. 6. Copper deficiency on Aglaonema. (Click image for expanded view).

Zinc deficiency has been identified in only one foliage plant, Chrysalidocarpus lutescens H. Wendl. (areca palm). Leaves of all ages become uniformly chlorotic and terminal leaves are triangular, stunted, and deformed.
Molybdenum is needed in small amounts by plants, but the use of soilless media and fertilizers lacking this element can result in deficiencies in poinsettia. Symptoms are similar to those of nitrogen or iron deficiency and ammonium toxicity. Plants may be stunted, leaves are small and chlorotic, and leaf margins may become scorched. Leaves tend to curl upward.

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