Composition

• Epsom salt, or magnesium sulfate, is composed of the minerals magnesium and sulfur, both essential for healthy plant growth. Magnesium and sulfur can be depleted from the soil through heavy field use or heavy rains.
  
  

Benefits of Magnesium

• According to the Epsom Salt Council, research has shown that magnesium is critical for seed germination, essential to the production of chlorophyll and a stimulant for the absorption of phosphorous and nitrogen. Cool Greenery maintains that the benefits of applying Epsom salt to your garden plants are most evident when your garden soil is deficient in magnesium.
  
  

Benefits of Sulfur

• Sulfur contributes to chlorophyll production in plants and aids in the absorption of the nutrients nitrogen, phosphorus, potassium, according to the Epsom Salt Council.
  
  

Overuse

• The Epsom Salt Council maintains that you cannot overuse Epsom salt in the garden because it does not remain in the soil. Research by Linda Chalker-Scott, associate professor and extension urban horticulturist, Washington State University Puyallup Research and Extension Center, on the other hand, warns that although magnesium is highly soluble in water, the dissolved magnesium ends up most often as a pollutant. Overuse of Epsom salt in the garden can cause runoff water pollution.
  
  

How to Apply

• The Epsom Salt Council recommends that Epsom salt be applied according to this regimen: for tomato plants, 1 tablespoon per foot of plant height every two weeks; roses, 1 tablespoon per foot of plant height applied every two weeks; shrubs, 1 tablespoon per 9 square feet applied over the root zone of the shrub every two to four weeks; lawns, 3 pounds for every 1,250 square feet applied with a spreader or diluted with water and applied with a sprayer; trees, 2 tablespoons per 9 square feet applied over the root zone three times a year.