Epsom salt, known chemically as magnesium sulfate, is frequently cited as a home remedy for various plant ailments. Many gardeners believe it provides a universal boost to citrus trees, encouraging greener leaves and better fruit production. This stems from the fact that citrus trees can suffer from magnesium deficiency, which Epsom salt directly addresses. Determining whether your tree actually requires this specific supplement, and applying it correctly, is the difference between a healthy tree and one with new nutrient problems. This article provides an evidence-based look at the specific conditions under which Epsom salt benefits citrus and how to use it safely.
The Role of Magnesium and Sulfur in Citrus Health
Epsom salt is a compound of two secondary macronutrients, magnesium (Mg) and sulfur (S), required in relatively large amounts by citrus trees. Magnesium is a constituent of the chlorophyll molecule, the pigment essential for photosynthesis. Without sufficient magnesium, the plant cannot produce chlorophyll efficiently, directly impacting the tree’s ability to grow and set fruit. Magnesium also acts as an activator for numerous plant enzymes and is involved in carbohydrate metabolism. This influences the movement of sugars produced in the leaves to developing fruit and roots. Sulfur is the other component of Epsom salt, necessary for the formation of proteins, certain plant hormones, and enzymes. Sulfur also works closely with nitrogen in the production of amino acids and chlorophyll, supporting overall plant structure and function.
Identifying Magnesium Deficiency in Citrus
Before applying Epsom salt, a grower must confirm that magnesium deficiency is the actual issue, as misdiagnosis can lead to new problems. The characteristic sign of a lack of magnesium is a specific pattern of chlorosis, or yellowing, that appears on the tree’s older leaves. Symptoms develop on these older leaves because the tree mobilizes the limited magnesium supply to support new growth and developing fruit. This chlorosis begins as yellowish-green blotches near the base of the leaf between the main veins. As the deficiency progresses, the yellowing spreads outward until only the midrib and the base of the leaf retain their green color, forming a distinct, inverted “V” shape. This visual pattern is a specific diagnostic indicator for magnesium deficiency, often referred to as “bronzing” when the yellowing takes on an orange-brown hue. If your citrus tree does not exhibit this exact pattern on its older leaves, the problem is likely caused by another nutrient deficiency or environmental stress.
Safe Application Rates and Methods
Once a magnesium deficiency is confirmed, Epsom salt can be applied through two primary methods: a foliar spray or a soil drench.
Foliar Spray Application
A foliar spray allows the magnesium to be absorbed directly through the leaves, providing immediate relief to the affected foliage. Dissolve 1 to 2 tablespoons of Epsom salt in one gallon of water. Spray this solution onto the leaves until thoroughly moistened, focusing on the underside where absorption is most effective. Apply when temperatures are mild to prevent leaf burn.
Soil Application
For a slower, more sustained correction, a soil drench or broadcast application is used. For a medium-sized tree, mix 1 to 2 tablespoons of Epsom salt into a gallon of water and apply the solution directly to the soil around the tree’s drip line. Alternatively, a mature tree may require a larger application, such as 75 grams of Epsom salt applied directly to the soil three times per year. The compound must be thoroughly watered into the soil to reach the roots. Applications should be repeated monthly or quarterly until symptoms are resolved and new growth is healthy.
When Epsom Salt is Not the Answer
Epsom salt is not a complete fertilizer, meaning it only supplies magnesium and sulfur and does not provide nitrogen, phosphorus, or potassium, which are required in greater quantities by citrus trees. Applying Epsom salt when the tree is not magnesium deficient can create new problems through a process known as nutrient antagonism. This occurs when an excess of one nutrient interferes with the uptake of others that share similar chemical properties. Specifically, excessive magnesium can inhibit a citrus tree’s ability to absorb other crucial nutrients, most notably calcium. Too much magnesium can lead to a calcium deficiency, which can cause new growth to be stunted or deformed. If the tree’s symptoms do not match the classic magnesium deficiency pattern, the issue may be a lack of other micronutrients like zinc or manganese, which cause different chlorosis patterns. Soil testing is the only definitive way to confirm which specific nutrients are lacking in the soil, preventing the misapplication of Epsom salt that could otherwise harm the tree.