Manganese Overload

Description

Manganese Overload is a condition which describes an African Violet that is getting too much manganese (Mn). While considered a micronutrient, manganese is essential to the growth and vitality of African Violets. It plays an important role in the function of photosynthesis, thus contributing to those processes which give African Violets their deep, green foliage. However, too much manganese can cause problems. Manganese Overload may be due to fertilizing with a formula that contains more than the recommended percentage of manganese. It may also be due to overfertilizing, in which case you will probably see additional symptoms.

Distinguishing Symptoms

• Leaves have brown spots on them. While other conditions may also cause brown spots on leaves, an excess of manganese is unique in that the brown spots it causes will be surrounded by a chlorotic circle, i.e., either yellow or light green in color. (Important: Do not confuse the brown spots caused by a Manganese Overload with those caused by Rhizoctonia.)

If your Violet exhibits this symptom, it may be suffering from a Manganese Overload. However, it is important to rule out other possible causes. (Note: After ruling out other possible causes, you should keep in mind that, due to the complex interaction between plant nutrients, it is often very difficult to pinpoint the precise element causing problems. Short of sending your plant to a laboratory for testing, you will probably have to be satisfied with simply knowing that your African Violet suffers a nutritional imbalance without knowing the exact elements involved. This said, do not be discouraged. The recommended treatment will remedy all nutritional problems.)

Treatment

First, repot your Violet with fresh potting soil. After separating the rootball from its container, shake as much of the old soil from the roots as you can without disturbing the roots too much. Repot the plant in a potting soil that is light, porous and guarantees a pH of 5.8 to 6.2.

Next, drench the soil with lukewarm water and let it drain. When doing this, add enough water until at least a cup (8 oz.) of water has drained from the pot. This will help leach out any of the excess fertilizer salts which may have accumulated in the soil. If these excess fertilizer salts were the cause of the problem, they may still be present in the old soil that clung to your Violet's roots.

After you let any excess water drain from the pot, wait one week. During this time, do not use a fertilizer. The nutrients in the soil will be sufficient until you begin fertilizing again.

After one week, you may notice that your Violet has already begun to recover. If this is the case, you can again start fertilizing. When selecting a fertilizer, be sure that it contains approximately equal amounts of the primary nutrients, nitrogen (N), phosphorus (P) and potassium (K). For standard-sized African Violets (in 3-inch pots or larger), an NPK of 14-12-14 is recommended. For Miniature Violets, you will need a fertilizer specifically formulated for miniature plants, such as Optimara Miniature Plant Food. In addition to being fully-dissolving, make sure that the nitrogen is not derived from urea, since urea will cause Root Burn on African Violets. Sources for each of the three primary elements can be found in the Guaranteed Analysis, located on the fertilizer label. (Note: Many of the micronutrients, though essential to the health of African Violets, are often not listed on the Guaranteed Analysis. If interested, reputable Violet Food producers will generally be happy to send you a complete analysis upon request.)

Important: If symptoms begin to return, you may have a problem with your water. Some common problems with water include too much chlorine in the water and soft water. If you suspect your water to be the problem, repeat the above steps and try using non-distilled, bottled spring water on your plants. If symptoms clear up, your water is almost certainly the problem. To be sure, you may want to have a sample of your water tested at a laboratory. If you do, have them check the levels of boron, zinc, molybdenum, potassium and chlorine. Aside from chlorinated and soft water, these are the most common elements which, if contained in excess in the water, can cause problems for African Violets.

Prevention

Use a recommended Violet Food or fertilizer specifically formulated for African Violets. Your Violet Food should be fully-dissolving and contain approximately equal amounts of the primary nutrients, nitrogen (N), phosphorus (P) and potassium (K). Miniature Violets generally need a slightly higher proportion of phosphorus, such as that contained in a 7-9-5 formula. Also, your Violet Food should not contain urea nitrogen, since urea causes Root Burn on African Violets.

Use a potting soil that is light, porous and guarantees a pH of 5.8 to 6.2. For best results, your potting soil will consist of mostly block-harvested, sphagnum peat moss. Other ingredients may be included to increase the porosity and stabilize the pH.

At least twice a year, repot your African Violet, using fresh potting soil.

About every three months, drench the soil with lukewarm water. To do this, water from the top until about a cup (8 oz.) of water has drained from the pot. Allow any excess water to drain.

For more about fertilizers and their effect on African Violets, see "Caring for African Violets."

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