Epsom salt, or magnesium sulfate, has a long reputation in easing aches and pains in humans but also has a reputation as a wonder drug for under-performing plants. Used in conjunction with all-purpose garden fertilizers, Epsom salt is primarily useful for correcting nutrient deficiencies in the soil, but should be used only to return plants to a baseline level of health rather than to increase performance, growth or flower production; or in the case of tomatoes, fruit yields.
About Epsom Salts
Epsom salt receives its common name from a spa destination town in England known around Europe from the late 1600s for its mineral waters. The village of Epsom was just one of several in the region known for producing these medicinal tonics, which were reputed to have numerous healing powers. Epsom salts are still used today in soaking baths to relieve pain associated with sore muscles and joints.
Epsom Salts in the Garden
Epsom salt's two elements, magnesium and sulfur, are both essential for strong plant growth. Magnesium is a critical component of the chlorophyll molecule, which all green plants use to harness power from sunlight; sulfur is an element taken up by plants in small quantities for use in synthesizing proteins. Plants growing in soils deficient in either of these elements will not perform to their maximum capacity, but sending a soil sample for testing is the only way to confirm the exact nutrient content of a given area.
Nutrient Deficiencies in Tomatoes
The yellowing of tomato leaves is a common occurrence during the regular growing season, and can be attributed to any number of pest, disease or drought problems. However, magnesium deficiency in the soil is a potential cause of tomato leaf chlorosis, or premature yellowing, and is one indication that Epsom salts may be called for to correct the deficiency.
Using Epsom Salts on Tomatoes
The tomato grower should take care to follow all recommended dosages on the package, as excess Epsom salts can build up in the top layer of soil when applied too generously over time. Using a mixture of general fertilizer with several tablespoons of Epsom salt dissolved in water is the usual method of feeding plants. Weak solutions of Epsom salt and fertilizer can also be used to feed seedling tomato plants in soil-less plant mix just after germination.
Effects of Improper Epsom Salt Usage
Though Epsom salts are also touted as an effective pesticide when sprayed onto the foliage of plants, more often than not this merely causes leaf burn; no impact on common tomato pests has been firmly demonstrated by studies carried out to this date. There is also little scientific evidence to suggest that Epsom salts will encourage tomatoes to grow larger or produce more fruit, so using a soil test to determine the minimum amount of salts to apply to the garden is essential to returning tomato plants to a normal state of health and growth.