The Good News: Epsom salts CAN have a purpose in the garden.
The Bad News: Epsom salts straight out of the package, as a granulated product in the soil, can be highly detrimental to plants!
The Right Way: ALWAYS dilute Epsom salts in water before using. Use this solution as a drench to the roots of the plants or in a spray bottle on the foliage.
What is Epsom Salts?
Mg can aid in intensifying plant color pigments as well as the green in foliage color. Rosarians apply it as a drench about 4 weeks prior to cutting their roses for rose shows to help enhance flower and foliage color.
Proper Soil Nutrition is a Delicate Balance
In soils with a pH of 6.5 or higher Epsom salts can be helpful to plants. Dilute the Epsom salt at a rate of 2 tbsp per gal. of water. This can be applied as a drench to the roots or sprayed onto the plant foliage.
Soil Testing Is Important!
Soil testing is the best and most effective tool to establish what the soil pH and nutrient level benchmarks are before any nutrient additives are applied. You do not want to add any nutrients like Epsom salts without making sure the plants will benefit from it! Plants can be adversely affected, especially Tomatoes if too much is applied!
Why is this important?
The sulfate component of Epsom salts can have the effect of lowering soil pH, so it is helpful to test the soil pH before any application is made. If the soil pH gets too low (5.5 or lower) this can interfere with vegetable crop performance and yields.
Excess amounts of Mg can interfere with calcium (Ca) absorption. Calcium is a nutrient component that helps prevent blossom end rot and other fruit-related ailments and disorders like cracking in tomatoes. Likewise, if calcium is in excess it interferes with Mg absorption along with the absorption of other micronutrients.
Contact your local county extension office to have a soil test done for a minimal cost. Or you can choose a DIY soil test kit.