Epsom salt, chemically known as magnesium sulfate, is occasionally recommended for plants as a source of magnesium and sulfur. Magnesium is an essential nutrient for plants, and dogwoods require it for healthy growth. However, magnesium deficiencies in dogwoods are relatively rare, especially in areas with balanced soils. Applying Epsom salt to dogwoods in the absence of a magnesium deficiency is unlikely to provide significant benefits.