Q: My parents have always told me to put Epsom salts on my roses and tomatoes to make them healthier. Does it really help? How much should I add?
A: Epsom salts is the common name for the chemical magnesium sulfate. The central atom in a chlorophyll molecule is magnesium, so plants definitely have a need for this element. By the way, if you replaced magnesium with iron in the chlorophyl molecule you’d have something very similar to heme, an important human blood constituent.
Gardeners have heard for years that Epsom salts be added to the soil to make plants healthier. However, if your soil has plenty of magnesium already, the Epsom salts won’t make much difference.
Dr. David Kissel, director of the University of Georgia Soils Lab, analyzed soil data for gardeners in the Piedmont region of Georgia and compared it to data from the sandy lower third of the state. In the Coastal Plain, only 12 percent of homeowners samples tested low, 21 percent tested medium, and 67 percent tested high in magnesium. In the Piedmont,17 percent of the samples were low, 33 percent medium, and 51 percent high.
In other words, more than half of Georgia gardeners would find no benefit to applying Epsom salts. For those who need it, a tablespoon per gallon of water once each month is about right. If you want your soil tested for its magnesium level, go to Georgia Soil Test.