How to Mix Epsom Salts as a Fertilizer

Epsom salts, or magnesium sulfate, offer a simple and affordable way to add magnesium and sulfur, two elements essential for plant health, to the soil. The inexpensive product is available at any drugstore and is usually mixed with water and then used as either a soil drench or a foliar spray. How Epsom salts are mixed and applied depends on the specific need, and the results you get may vary.

Adding Epsom salts has proved beneficial in cases of magnesium-deficient soil. In some cases this is just the result of the soil makeup and is common in very light or sandy soils. It can also be a condition that occurs as a result of heavy rainfall or watering to the point that the magnesium is leached from the soil. In such cases Epsom salts can restore magnesium to the soil. The salts may also boost the growth of roses, peppers, tomatoes, lawns and other plants.

If your plants develop leaves that are yellow in the areas between the veins, a condition known as interveinal chlorosis, it may be due to a lack of magnesium in the soil. It’s possible to correct such a deficiency with Epsom salts. Experts at Auburn University’s Department of Horticulture recommend mixing 1/2 to 1 full ounce of Epsom salts in 3 gallons of water and applying it to the soil.

Brenda Larson of the North Carolina State University Cooperative Extension points out that Epsom salts can be used to boost the growth of roses. She advises gardeners to mix 1/2 cup of Epsom salts into enough water to dissolve the salts and use the mixture to water the roses early in the spring. A mixture of 1 tablespoon of Epsom salts and 1 gallon of water can be sprayed on roses as a foliar fertilizer once every two weeks during the growing season, but avoid spraying on sunny days or the plants may burn.

A "Green Mountain Gardener" article in the University of Vermont Extension’s summer newsletter states that peppers and tomatoes can benefit from the addition of Epsom salts. Combine 1 tablespoon of Epsom salts with a gallon of water and spray the plants with it when they are first transplanted, when they first flower and when they set fruit. Epsom salts can also be applied directly to lawns to help them grow greener. Dissolve 2 tablespoons of the crystals per gallon of water and apply it to your lawn, using enough of the mixture to wet the entire lawn. Follow up with a thorough soaking using nontreated water to ensure the salts sink into the soil. You can also use a spreader, applying about 3 pounds of Epsom salts per 1,250-square-foot area.