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Potting Soil - pH Imbalance


pH is short for puissance de hydrogen and refers to the measure of acidity or alkalinity of any substance. A pH below 7.0 is considered acidic, while a pH above 7.0 is alkaline. Correct soil pH is vital for the health and performance of African Violets. Optimum soil pH ranges from 5.8 and 6.2. A good potting soil, which has been blended especially for African Violets, will have the correct pH. However, there are other factors which can affect pH, such as concentrations of fertilizer salts and soft water. If the pH of the potting soil varies too much from 5.8 to 6.2, your African Violet will not be able to absorb the proper amount of nutrients it needs. For instance, high pH can result in a decifiency of iron, whereas low pH can result in a deficiency in phosphorus.

Distinguishing Symptoms

Due to the complex interaction between the soil pH and plant nutrients, it will be difficult for most to distinguish symptoms arising from a pH imbalance from those due to a simple lack of available nutrients. However, there is at least one instance when you can be certain that a pH imbalance is playing a role. If you are using soft water to water your Violet, it is almost certainly suffering from a pH imbalance in the soil. Aside from this, and short of sending your Violet to a laboratory for testing, you will probably have to be satisfied with the knowledge that your Violet is suffering from a lack of nutrients, whether or not it is caused by a pH imbalance in the soil. This said, do not be discouraged. Regardless of the cause, the problem can be successfully treated. (See below.)

Other Symptoms

Listed below are some of the symptoms you may encounter from a pH imbalance in the soil. Accompanying these symptoms are some of the specific elements which your Violet may be unable to absorb due to a pH imbalance.


Assuming that you have ruled out other possible causes for the symptoms you are encountering, your best course of action assumes that your Violet is suffering from a general lack of nutrients and that a pH imbalance in the soil may or may not be the cause of it. With this in mind, here is what you should do.

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. Water from the top until about a cup (8 oz.) of water has drained from the pot. Allow any excess water to drain. This will help leach out any of the substances that may have contributed to a pH imbalance. If these substances were the cause of the problem, they may still be present in the old soil that clung to your Violet's roots.

After you have drenched the soil, 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 it has, it was most likely suffering from a pH imbalance in the soil. In either 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, too much boron 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. These are the most likely causes of problems for plants.


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 soil with lukewarm water to leach out any unwanted concentrations of fertilizer salts. 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.

Do not use soft water. Soft water increases the saline content in your potting soil. This will alter both the pH and the electrical conductivity of the soil, thereby affecting an African Violet's ability to absorb water and nutrients.

Finally, if the pH of your potting soil is a recurring concern, you may want to measure the pH from time to time. Reasonably inexpensive pH test kits are available at most garden centers. For African Violets, the pH should measure between 5.8 and 6.2.

For more about potting soils, pH and the proper absorption of nutrients, see "Caring for African Violets."

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