Although I’ve never tried Epsom salts, named for a town in England, in my landscape or garden, I’ve heard many gardeners rave about what they call a miracle cure for plants. Whenever I wonder about whether something is a horticulture myth, I turn to Linda Chalker-Scott, Ph.D., a well-respected horticulture researcher at Washington State University. According to Chalker-Scott, Epsom salts application can be justified in specific incidences when plants are under intensive crop production and magnesium (Mg) is known to be deficient in soil or in plants.
Magnesium sulfate (MgSO4 or Epsom salts) is used worldwide to “relieve Mg deficiency during intensive cropping of many fruits and vegetables including apples, beets, carrots, cauliflower, kale, peppers, plums, potatoes, snap beans, tomatoes, watermelons and wine grapes.” Conifers in intensive plantings have been treated successfully with MgSO4 to improve Mg deficiency. Short-term improvements have also been seen in Mg-deficient turf.
The two primary reasons for Mg deficiency are either an actual lack in a soil or mineral imbalances in a soil or plant. For example, too much potassium in a soil can interfere with Mg uptake by roots. Mg deficiency is most common in light, sandy and/or acid soils. There are problems with adding Epsom salts to a soil or to a plant. From a soil perspective, Epsom salts are highly soluble and easily leached from the soil by rain or irrigation. This can contaminate groundwater or surface waters via creeks, rivers or drainages. As for plants, the salts can scorch leaves when applied as a foliar spray, although adding a wetting agent might reduce this adverse response.
Most of the claims of miracle cures with Epsom salts application aren’t substantiated by research, but many lifelong gardeners swear by this product and reports of efficacy are handed down through generations. No, Epsom salts don’t control grasshoppers in beans, caterpillar pests on tomatoes, slugs, voles, rabbits or any other pests. There has been no research to support the claim they control diseases either. No, they don’t influence seed germination, because seeds germinate without external nutrients. Adding Epsom salts to “adequately-fertilized plants will not increase chlorophyll production” or make plants bushier because “any source of available sulfur or magnesium will improve nutrient uptake and usage.”
While using a household product seems like a great idea, ask first, “Is it necessary?” And then, “Will it do any damage, either to the plant or the environment?”
For information, go to https://s3.wp.wsu.edu/uploads/sites/403/2015/03/epsom-salts.pdf.
JoAnne Skelly is associate professor and Extension educator, Emerita at University of Nevada Cooperative Extension. She can be reached at firstname.lastname@example.org.