By Julie Christensen

You’ve used Epsom salts for aching muscles in the tub, but Epsom salts in the garden? If this sounds far-fetched, consider that test gardeners from the National Gardening Association noticed significant improvements in their gardens after using Epsom salts. But, like any garden supplement, Epsom salts have their limitations and work best on certain plants and in certain conditions. Read on for the low-down on this inexpensive gardening solution.

Epsom salts aren’t really salt at all, but natural mineral deposits found in the water in Epsom, England. Their chemical composition is hydrated magnesium sulfate. Plants need magnesium to build strong cell walls and fruit. Magnesium also helps plants use nitrogen, sulfur and phosphorus.

You can get Epsom Salt at drug stores, and online.

Plants use sulfur to produce amino acids and vitamins. Sulfur is also the compound that gives many vegetables, including broccoli and onions, their distinctive flavor. Most garden soils have sufficient levels of sulfur, but magnesium deficiencies are common, especially in old, acidic soils and the highly alkaline soils found in the western states.

Severe magnesium deficiencies can cause stunted growth and yellowing of the leaves between the veins. However, the only symptom you might see is slow growth and fewer blossoms or fruit. Soil tests can detect severe magnesium deficiencies. In some cases, though, a soil test might reveal that your soil has adequate magnesium, yet plants are unable to access it due to high levels of potassium and calcium.

Intrigued? If you’d like to try Epsom salts on your garden, consider the following:

• Test gardeners from the National Gardening Association found that they obtained the best results from foliar applications, rather than amending the soil with Epsom salts. You’re also less likely to damage the soil using this method.
• Epsom salts made the largest difference on tomatoes, peppers and roses. Test gardeners found that their tomato and pepper plants were larger, greener and produced more fruit. The fruit had thicker, juicier walls and tasted sweeter. Roses had greener leaves and more abundant, larger flowers.

Directions for Using Epsom Salt for Gardening

If you know your soil is low in magnesium, try sprinkling ½ cup granules around the base of your roses in the spring as new growth emerges. Apply an additional ½ cup in the fall before the leaves drop. During the growing season, dilute 1 tablespoon Epsom salts with 1 of gallon water. Spray the roses after the leaves emerge and again during flowering.

To treat tomatoes and peppers, dilute 1 tablespoon Epsom salts with 1 gallon of water. Spray the plants after transplanting, when they first flower and when they begin producing fruit. In addition to producing more abundant fruits, Epsom salts can also reduce problems with blossom-end rot, which are believed to be caused partially by a magnesium deficiency.

If you’re not sure if you have a magnesium deficiency, skip the soil applications and stick to foliar applications instead.

As with any gardening amendments, it’s best to take a cautious approach with Epsom salts. Scientific research on their use is largely unavailable, except in intensely cultivated agriculture, where they have been shown to provide benefits. Although Epsom salts probably won’t damage your soil, they might be a waste of money. Use them on the plants recommended above and conduct a soil test every three years so you know exactly what nutrients your soil is missing.

To learn more about using Epsom salts, visit the following sites:

Fertilize with Epsom Salts from the National Gardening Association

Epsom Salts Benefits Gardens from the Epsom Salt Council

Julie Christensen learned about gardening on her grandfather’s farm and mother’s vegetable garden in southern Idaho. Today, she lives and gardens on the high plains of Colorado. When she’s not digging in the dirt, Julie writes about food, education, parenting and gardening.