The two major ingredients in Epsom salt are sulfur and magnesium. According to the Epsom Salt Council, both are critical to plant development and promote chlorophyll production and aid in the absorption of vital nutrients from the soil. Soil with deficiencies of either sulfur or magnesium may produce plants with inhibited growth.
Many gardeners mistakenly believe that Epsom salt provides added nutrients that benefit tomatoes regardless of the condition of the soil. Healthy soil high in organic matter rarely requires additional applications of either magnesium or sulfur. But some soils may suffer deficiencies that can be effectively treated with Epsom salt, leading gardeners to believe it is responsible for rapid growth and abundant fruit.
How It Works
Epsom salt replaces the magnesium and sulfur in the soil. Deficiencies in magnesium and sulfur make it difficult for plants to absorb nutrients they need for vigorous growth. Once the deficiency is corrected, tomato plants show rapid growth with robust stems and abundant fruit.
Epsom salt mixed with water and applied as a foliar feeder works quickly to restore magnesium to tomato plants that suffer from a magnesium deficiency. Complete coverage is recommended, and repeat applications may be necessary. Epsom salt applied to the soil processes more slowly than foliage feeders but provides the same benefits.
Epsom salt can be applied either to soil or mixed and applied as a foliage feeder with a sprayer. Mix one cup of Epsom salt to 1 gallon of water and dissolve thoroughly to use as foliar feeder. For applying to the soil, use 1 tablespoon for each foot of height of the tomato plant and mix it into the soil around the base of the plant. Apply every 14 days.
Epsom salt does not build up in the soil and poses no dangers of over fertilization. It is inexpensive and does not pose the risks associated with chemical fertilizers. Epsom salt is safe for the skin, but should be kept out of the reach of small children and pets. Many gardeners prefer to use Epsom salt as green alternative to chemicals.