Gardening Articles: Care :: Soil, Water, & Fertilizer

Fertilize with Epsom Salts (page 2 of 3)

by Charlie Nardozzi

What Our Testers Found

To get a first-hand look at the effectiveness of Epsom salts in the garden, we asked six of our testers (in California, Colorado, Iowa, Pennsylvania, and Tennessee) to try Epsom salts on peppers and roses. Testers each grew six 'Gypsy' peppers. They applied 1 tablespoon of Epsom salts mixed with a gallon of water as a foliar spray to three plants at bloom time and again 10 days later. They also selected two established rose bushes of the same variety and sprayed the same amount of Epsom salts mixed with water to one bush every 6 weeks, starting when leaves came out and continuing through the summer (about 4 applications). We asked them to record the number of pepper fruits and rose blooms, and to note any differences they saw.

Four out of the six testers reported that the Epsom salts-treated pepper plants and fruits were larger than the controls. For the treated roses, testers reported greener foliage, bushier plants, and more roses than on the control plants.

Kathy Stone Downie of Alameda, California, noticed many differences in her treated 'Gypsy' peppers. "The fruits were much bigger, almost twice the size. They were juicier, sweeter, and triple the thickness of the untreated peppers." Tommy Owen, in Rogersville, Tennessee, said that his treated roses had greener foliage and bigger flowers with deeper colors.

Recent Studies of Epsom Salts

Scientists are beginning to test its use. Although many studies confirm that magnesium sulfate is a good way to supply magnesium and sulfur to soils deficient in those elements, little research has been done on the use of Epsom salts as a supplemental fertilizer on soils with adequate levels of these nutrients.

Renee Schloupt, horticulturist at Delaware Valley College in Doylestown, Pennsylvania, is testing peppers and tomatoes grown in a greenhouse environment under drought and nondrought conditions. She's comparing control plants with those watered with applications of 1, 2, and 3 tablespoons of Epsom salts mixed with 1 gallon of water and applied at planting, flowering, and fruit set. So far, she has not seen any measurable evidence of growth or yield differences in the treated tomatoes or peppers. "The peppers have greener leaves, and it seems the 1- and 2-tablespoon doses yield a better result than the 3-tablespoon dose, but I haven't seen any dramatic effects on yields so far," she says. "The magnesium in the Epsom salts applied to the soil could be getting tied up with other nutrients. We might see better results when we apply Epsom salts directly to the leaves."

At Auburn University in Alabama, plant pathologist Kira Bowen and soil scientist Beth Guertal see similar results when they apply Epsom salts directly on the soil. They are conducting a 3-year study of roses in field plots that includes applying 1 cup of Epsom salts per plant per month as one of the treatments to increase plant vigor and control black spot. "The first year, we saw reduced defoliation in the Epsom salts-treated plants, but the second year the differences weren't there," Bowen reports. "It's hard to find a direct link between a specific nutrient such as magnesium sulfate and increased yield or plant growth because of all the other variables in the soil, such as pH, calcium and potassium content, and weather, that may affect the plants."

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