Giving Your Plants A Boost With Epsom Salts

Published: 28th March 2009
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Use this old household remedy to give some plants a boost.

Many gardeners are familiar with benefits of applying Epsom salts to tomatoes, peppers, and roses but if you are not then let me explain the benefits. The purpose is to improve magnesium content in the soil but is also used as a foliar feed, in order to have healthier foliage, bushier plants and to improve the yield and size of flowers and fruits.

The History and Science of Epsom salts

Epsom salts are a natural mineral, discovered in the well water of Epsom, England, and has been used for hundreds of years, not only to fertilize plants but also to treat a range of human and animal ailments. Chemically, Epsom salts is hydrated magnesium sulphate (about 10 percent magnesium and 13 percent sulphur). 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 sulphur. Sulphur, 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 flavours. Sulphur is seldom deficient in garden soils because acid rain and commonly used animal manures contain sulphur, as do chemical fertilizers such as ammonium sulphate.

The causes and effects of magnesium deficiencies vary. Vegetables such as beans, peas, lettuce, and spinach can grow and produce good yields in soils with low magnesium levels, but plants such as tomatoes, peppers, and roses need high doses 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. Gardeners add magnesium when they apply dolomitic lime to raise the soil's pH.

However, this product (46 percent calcium carbonate, 38 percent magnesium carbonate) breaks down slowly, and the calcium can interfere with magnesium uptake. For soils with a pH above 7, many gardeners use Sul-Po-Mag (22 percent sulphur, 22 percent potassium, 11 percent magnesium) to increase magnesium. Although dolomitic lime and Sul-Po-Mag are inexpensive ways to add magnesium, Epsom salts' advantage over them is its high solubility.

Applications of Epsom salts can be given to the degree of 1 or 2 tablespoons of Epsom salts mixed with 1 gallon of water and applied at planting, and as a foliar feed at flowering time and fruit set.


Many rose growers agree that Epsom salts produces more new canes at the bottom of the plant (bottom breaks) and darker green foliage. Recommendations on how much to use vary, but generally you can apply 1/2 cup of granules in spring before buds first begin to open and 1/2 cup in autumn before leaves drop. Apply a foliar spray (1 tablespoon per gallon of water per foot of shrub height) after the leaves open in spring and again at flowering.

Tomato and Peppers

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.

However, don't rely on Epsom salts alone to correct large soil magnesium deficiencies, but rather use it as a supplement to soils with adequate or slightly low magnesium levels to boost plant growth, flowering, and fruiting. For severely magnesium-deficient soils, use dolomite lime or Sul-Po-Mag.

Information on birds nest fern can be found at the Plants And Flowers site.

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