Your grandmother may keep a box of Epsom salts in her medicine cabinet, as a foot soak, or as a cheap and effective laxative. If you find a box of Epsom salts in her shed, however, it's a good bet she uses them in her vegetable garden. Because of its mineral content, Epsom salt is especially useful to enrich the soil to make nutrients available to plants.
Components of Epsom Salt
According to the Epsom Salt Council, Epsom salts contain magnesium and sulfur, two essential components in good garden health. Magnesium is necessary for seed germination, so if the soil is deficient, seeds will not sprout. Magnesium also helps in the absorption of phosphorus and nitrogen, which are two vital fertilizer ingredients. The organization also asserts that magnesium is crucial in the production of chlorophyll, the substance that plants use to make food from sunlight. Sulfur appears to help in chlorophyll production and also makes the three primary nutrients in the soil -- nitrogen, phosphorous and potassium -- more effective, making plants healthier and stronger.
Reasons for Use
Magnesium and sulfur are natural components in the soil, but if these nutrients are depleted, you must replenish them or your vegetables will not grow. Epsom salts are also natural, and do not accumulate with prolonged use. This is one benefit to using the mineral, as accumulation of commercial fertilizers occurs over time, which can diminish soil quality. The National Gardening Association conducted tests with six gardeners in five states who grew gypsy peppers. Of those six gardeners, four reported that using Epsom salts in addition to fertilizer resulted in larger pepper plants than the plants grown using only fertilizer.
Epsom Salt in the Garden
Epsom salts do not appear to be a cure-all, but more of a supplement to existing soil and plant treatments. The salts do best in soils that are deficient in magnesium, are highly alkaline or highly acidic and have high calcium and potassium content. The treatment works for most crops in a vegetable garden, but National Gardening Association research indicates that tomatoes and peppers respond the best.
For peppers, mix 1 tbsp. of Epsom salt with a gallon of water. Spray the mixture directly on the plant when it is in full bloom and once more ten days later. For tomatoes, the Epsom Salt Council recommends sprinkling the salts directly on the soil at the base of the plant: Use 1 tbsp. per foot of the plant. If your tomato plant is 2 feet high, use 2 tbsp. For general garden use, test your soil first to determine if you have any nutrient deficiencies, and then apply as needed.
Vegetable gardens are prone to damaging insects but evidence is mixed regarding Epsom salt's effectiveness as a natural pesticide. Washington State University horticulturalist Linda Chalker-Scott conducted research into the effectiveness of Epsom salts as a garden pesticide and found no discernable reduction in insect invaders by using the substance. An old recipe of epsom salts, molasses, bran and water has been touted for more than 60 years as being an effective insecticide, however Chalker-Scott's more recent research indicates that this method is ineffective against garden pests.