Epsom salt is magnesium sulfate, MgSO4, and should not be confused with common salt, sodium chloride NaCl. Magnesium and sulfur are both natural minerals that many plants need to thrive. I have used Epsom salts in my garden for years and am very pleased with the obvious results of increased plant vigor, more blooms, larger blooms, greener foliage, and overall better plant health. This is especially true of my roses.