Are Epsom salts truly good for plants? The internet is filled with articles about how great they are for your garden, but is there any evidence that this is true? Let’s see what the research shows.
This is part of a series on common garden myths and advice, and what the facts show.
What Epsom Salts Really Do
NEW! Click play to listen:
You’ll hear gardeners gush about the benefits of Epsom salts (magnesium sulfate) as a solution for, well, pretty much everything: more vibrant flowers, greater yields for veggies, better seed germination, increased nitrogen uptake, vitamin production, sweeter tomatoes, pest control, weed control, greener leaves and so on and so on.
Well, who wouldn’t want to use something so amazing in their garden?
Only problem is, there’s really no evidence for any of this.
Epsom salts will add magnesium and sulphur to your garden. That’s true.
But the chances are your garden soil is not deficient in either of these things.
As a fertilizer, Epsom salts are very limited. They don’t provide any nitrogen, phosphorus or potassium—the macro-nutrient NPKs of fertilizers (see more on Fertilizers for Organic Gardeners here). They do provide magnesium and sulphur, which are not in high demand by your plants, and adding more will likely be of no benefit.
As a weed killer, along with the dish soap and other household items suggested in countless homemade weed killer recipes online, take a step back and consider what it is you are putting into your garden and the environment and why.
Just because it’s in your kitchen cupboard does not make it safe, beneficial, or harmless for the garden. And there are no specific properties in these things that target weeds.
Basically, it’s the same as tossing a bunch of random things in the garden and hoping they somehow smother the problem. And it’s all stuff that has no business in a living, thriving garden.
To me, the Epsom salt garden folklore does nothing more than sell a lot of Epsom salts.
Get a Soil Test to Measure What Your Garden Needs
If you are wanting to improve your soil, a soil test by a local laboratory can help determine any deficiencies.
Otherwise, if you are using good potting mix in containers or keep your garden soil fed with annual applications of compost, soil quality at a micronutrient level may not ever be an issue.
Consider the Big Picture
Theoretically, you could even do harm to your garden by adding too much Epsom salts—excess magnesium can create deficiencies in other nutrients—and Epsom salts are highly soluble, which means they can get into groundwater where they can end up in rivers and lakes, and that’s not good for the environment.
It may be trivial for one gardener, but imagine thousands or millions adding Epsom salts. That adds up.
And, that’s on top of the environmental costs of producing and distributing the Epsom salts in the first place. All for something that will likely do no good in your garden.
Correlation is Not Cause
If you grow beautiful roses or fabulous tomatoes and you did add Epsom salts to the soil, it might be easy to convince yourself they were the cause.
But, the best evidence we have is that Epsom salts just don’t deserve the credit you may be giving them.
If nothing else, the roses (or tomatoes or whatever) probably did well despite them.
The fact that no researchers can duplicate these results and professional growers don’t use them is a big hint that something else contributed to your success, not the Epsom salts.
If you know someone who swears by them, see if they’ll consider all the other good plant care habits minus the Epsom salts.
It’s the basics like adequate sun, water, air, soil, and the plant itself that work in harmony to create optimum growing conditions.
Unless there is a proven magnesium deficiency, which we know is uncommon, they can spend their garden money elsewhere and still have healthy plants.
And no, smothering weeds with a bunch of household stuff is not a recommended solution either. If you want to read more, see What Vinegar Really Does to Weeds and these 7 Weeding Tips Every Gardener Should Know.
I’d love it if there were magic bullets and easy answers for everything too, but gardening and life have other plans.
- Epsom Salts are Not Recommended: Unnecessary, Potentially Damaging | University of Saskatchewan
- Epsom Salt Use in Home Gardens and Landscapes | PDF format | Washington State University Extension
- The Epsom Salt Myth | NDSU
~Melissa the Empress of Dirt ♛