From our perspective as plants, our primary nutritional needs are met through a balanced supply of macro and micronutrients, typically found in a quality fertilizer. Magnesium (Mg) is a crucial core component of the chlorophyll molecule, the very pigment that allows us to capture light energy for photosynthesis. Sulfur (S) is a key element in the synthesis of amino acids, proteins, and vitamins. A deficiency in either nutrient can indeed manifest as interveinal chlorosis (yellowing between the leaf veins while the veins remain green) or overall stunted, pale growth. Therefore, the theoretical basis for using Epsom salt (chemically known as magnesium sulfate) is sound: it directly supplies these two specific elements.
However, our growing medium and your regular feeding habits dictate whether this supplemental dose is a necessary treatment or an unnecessary risk. Most commercially available potting mixes and specialized African violet fertilizers are already fortified with a balanced array of nutrients, including sufficient amounts of magnesium and sulfur for our needs. Applying Epsom salt when no deficiency exists is, from our root system's point of view, an act of chemical force-feeding. It disrupts the delicate osmotic balance we work hard to maintain. This can lead to a buildup of salts in the soil, which makes it harder for our roots to absorb water, effectively inducing drought stress and potentially causing root burn.
The most significant danger from our standpoint is the induction of a nutrient imbalance. The plant's metabolic pathways are finely tuned. An excessive concentration of magnesium in the soil solution can interfere with our ability to uptake other essential cations, most critically calcium (Ca). This magnesium-calcium antagonism can lead to a calcium deficiency, which manifests as distorted new growth, weak flower stems (blossom blast), and necrotic spots on young leaves—problems often mistaken for other issues. You might be trying to solve a problem that doesn't exist while simultaneously creating a new, more serious one for us.
The use of Epsom salt should be viewed as a targeted medical treatment, not a regular health tonic. If you observe clear symptoms of a magnesium deficiency—such as widespread yellowing between the veins of older leaves while the veins themselves stay green, and you can confirm your regular fertilizer is low in Mg—then a cautious, diluted application may be beneficial. A solution of one teaspoon of Epsom salt per gallon of water, applied in place of a regular watering once a month, can help alleviate the specific deficiency. It is not a substitute for a balanced fertilizer and should be discontinued once the symptoms correct themselves.
