I was cleaning out the cupboard the other day and found a container of Epsom salt.

Probably left over from when our kids played sports. I remembered hearing that Epsom salt was good for tomatoes and decided to do a little research. I wondered if it was one of those home remedies or was there any real value.

Gardeners apply it to tomatoes, peppers, and roses, hoping to produce more flowers, greener plants, and higher yields. You can use it to improve magnesium content if you know you have a soil that’s deficient in that element, but home gardeners are most likely to apply Epsom salts to peppers, tomatoes, and roses.

This natural mineral, discovered in the well water of Epsom, England, has been used for hundreds of years, not only to fertilize plants but to treat a range of human and animal ailments. Who hasn’t soaked sore feet in it at least once?

Chemically, Epsom salts is hydrated magnesium sulfate (about 10 percent magnesium and 13 percent sulfur). Magnesium is critical for seed germination and the production of chlorophyll, fruit, and nuts. Magnesium helps strengthen cell walls and improves plants’ uptake of nitrogen, phosphorus, and sulfur.

Sulfur, a key element in plant growth, is critical to production of vitamins, amino acids (therefore protein), and enzymes. It’s also the compound that gives vegetables such as broccoli and onions their flavors. Sulfur is seldom deficient in garden soils in North America because acid rain and commonly used animal manures contain sulfur, as do chemical fertilizers such as ammonium sulfate.

Plants such as tomatoes, peppers, and roses need high levels of magnesium for optimal growth. However, plants may not show the effects of magnesium deficiency until it’s severe. Some common deficiency symptoms are yellowing of the leaves between the veins, leaf curling, stunted growth, and lack of sweetness in the fruit.

Magnesium tends to be lacking in old, weathered soils with low pH, notably in the Southeast and Pacific Northwest. Soils with a pH above 7 and soils high in calcium and potassium also generally have low magnesium levels. Calcium and potassium compete with magnesium for uptake by plant roots, and magnesium often loses. Sometimes, a soil test will show adequate magnesium levels in soil, but a plant grown in that soil may still be deficient because of that competition.

When diluted with water, and especially when applied as a foliar spray, Epsom salts can be taken up quickly by plants. Epsom salts’ magnesium content, high solubility, and ease of application as a foliar spray are the main reasons for the positive results many gardeners see in their plants.

Magnesium deficiency in the soil may be one reason your tomato leaves yellow between the leaf veins late in the season and fruit production slows down. Test your soil every 3 years or so to check on nutrient levels. Epsom salts can keep plants greener and bushier, enhance production of healthier fruit later in the season, and potentially help reduce blossom-end rot. Apply 1 tablespoon of granules around each transplant, or spray a solution of 1 tablespoon Epsom salts per gallon of water at transplanting, first flowering, and fruit set.

From the various research I read the gardeners that tried Epsom salts had better luck spraying the leaves than applying to the soil.

I  gave it a try. I had the tomatoes and I had the Epsom salt on hand. I’ll let you know if I see any difference!

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