What's the Deal with Epsom Salts?
Q. A couple years ago Carol in Chesapeake Virginia emailed about a sudden and severe snail problem she was having with her container grown flowers. She wrote: "I have tried beer, coffee grounds, Epsom salts, Escar-Go slug repellant, Vaseline around the tops of the pots, moth balls, garlic spray, eggshells and the 'balls' from sweetgum trees, but nothing has worked up to this point!"
A. Must have been wet year in Tidewater! Among my responses back then were "never use mothballs for anything; they are nasty little cancer bombs." I added that beer traps work very well when used correctly, I added copper barriers to the 'useful slug-stopping' list and mentioned that I thought I had heard every possible use for those mysterious 'Epsom salts', but murdering mollusks was a new one for me.
Q. Brad in Annapolis wrote looking for help with his "Deformed Tomato Plants". As he explained, "They are growing in essentially flat soil and have been fed an organic tomato food. At planting time, I mixed the native soil 50/50 with a Humus and Manure blend and added a tablespoon or so of Epsom salts for each plant. Now they look like they've been exposed to an herbicide, with leaves curling up like a fern when it first gets growing."
Q. About the same time, Karen in Tryon North Carolina wrote: "I just got an email from a company that sells seeds and they recommend adding Epsom Salts to my garden soil. I was wondering what your opinion is on this."
A. I've been wondering the same thing for decades, Karen! Epsom salts are always in the top ten of audience questions I've come to expect when I do a public appearance: "My mother sprinkled a tablespoon of Epsom salts around her roses several times a season"; "my grandfather added Epsom salts to the planting holes for his tomatoes every year" and various variations thereof. Plus, the most popular one: "are Epsom salts organic?"
The only answer I had for this seemingly innocent death trap of a question was to say "technically no; Epson salts aren't an organic amendment because they're a combination of two chemicals that are manufactured in a lab. But it also seems to be harmless; AND it seems like half the world is using it in the garden, so I'd call it a technical organic 'no', but not worth making an issue out of." Then I would swear to make a mental note to research the subject when I got home, but there were always cartoons on TV when I got home; and, as we all know, mental notes aren't worth the paper they're not written on.
But just a few days ago (as the crows fly) I got an email from the National Garden Bureau; a non-profit organization dedicated to getting more people to garden; AND whose members represent a good 90 percent of the nation's seed, live plant and garden tool suppliers. The headline? "Epsom salts in the Garden...Good or Bad?" So, using this as a springboard, down the research rabbit hole I went, chasing knowledge, rumor, old timey wisdom and the writings of many people with questionable memories. (And it's always nice if you come across a juicy scandal along the way.)
The author of the article, "tomato expert" Daniel S. Goodspeed from the venerable J. W. Jung Seed Company, explains much in few words, quickly revealing that the revered substance whose legal name is Magnesium Sulfate DOES have actual value in the garden, and that the benefits it conveys are correctly attributed to the two plants to whom it is most often linked: roses and tomatoes, but only when used as a dilute liquid 'drench' and never in the form of the solid material that most 'pass along' stories cite. In fact, a couple of tablespoons of actual undiluted Epsom Salts can harm plants.
In a nutshell, he explains that Epsom salts are 10 percent magnesium, a vital plant micro-nutrient that, when applied in liquid form as a soil drench, helps plants better absorb a host of vital nutrients and improves the color of both fruit and foliage. Rosarians, we are told, will give their plants a drench a month before showtime, to help their flowers look the best. Two tablespoons thoroughly dissolved in a gallon of water is the right dose. But applying Epsom salts as a solid or in higher concentrations can block the plants' absorption of calcium, leading to cracking and blossom end rot on tomatoes. It can also lower the pH of your soil.
A curious website named "Apartment Therapy" answered MY big question: How and when did Epsom Salts come into our collective lives? In the British town of Epsom, of course! Located in the Surrey Hills region South of London, it was here in 1618 that a cowherder found a well whose water was so bitter tasing that his thirsty cows refused to drink from it. From there, we were off and running--literally, as the naturally-occurring Magnesium Sulfate turned out to be a potent laxative. Then it was also found to have soothing and healing powers when added to bathwater. Soon, Epsom was a spa town where people flocked to 'take the waters' one way or another.
But alas, the well ran dry and blocked-up Brits soon turned to the manufactured version we know today.