What Plants Don't Like Epsom Salt
Many gardeners ask us about using Epsom salts in the garden: Which plants don’t like Epsom salts? Will Epsom salts kill plants? We’re here to tell you that Epsom salts are good for neither plants nor soil! Yes, it’s one of those gardening myths. Learn more about how Epsom salt works and also some alternatives.
Most gardeners love a reliable home remedy and are eager to embrace a magic bullet. This is the case with Epsom salts. They are supposed to make flowering plants bushier and blossom more and make peppers and tomatoes more productive. But are they really a miracle cure? Can Epsom salts be harmful? Let’s separate myth from reality.
What Is Epsom Salt?
Epsom salt is the chemical magnesium sulfate (MgSO4)—which means both magnesium (about 10%) and sulfur (about 13%).
- Magnesium is needed by plants to generate the chlorophyll needed for photosynthesis. On a plant lacking magnesium, the older leaves will turn yellow between the veins and along the edges and growth will be stunted. Sandy, light, low pH soils are prone to magnesium deficiency. If your soil is quickly leached by rainfall and has a pH of 5.5 or less, it probably lacks sufficient magnesium. The addition of compost to raise the level of organic matter in the soil will help.
- Sulfur is needed to form some vitamins and plant proteins. If a plant lacks sulfur the young leaves will turn yellow. Sulfur also gives vegetables such as broccoli, onions, and mustard greens their flavors. Sulfur is seldom deficient in garden soils in North America so deficiencies are rare. Plus, if sulfur is overdone, it will build up in the soil and make it hard for plants to make use of the other nutrients they need. If you are lacking sulfur, manure is a good organic source.
Is Epsom Salt Good for Plants?
Bottom-line: No, epsom salt is not beneficial for plants.
- One reason people use Epsom salts is to prevent blossom-end rot. This isn’t true. In fact, Epsom salts can be harmful! Why? Blossom-end rot is caused by a calcium deficiency, not magnesium or sulfur deficiency. And adding too much magnesium to your soil can actually prevent calcium uptake!
- While many vegetables (leafy greens, beans, peas) can grow in soil with low magnesium levels, other plants including tomatoes, peppers, and roses need high levels of magnesium. So what if Epsom salt is added to the soil to correct large soil magnesium deficiencies? Unfortunately, horticultural studies (Auburn University, Delaware Valley College) prove that adding Epsom salts to the soil (directly or through watering) does not link to higher yield or healthier growth from peppers and tomatoes to roses. When it comes to your soil, do not rely on Epsom salts to adjust deficiencies in magnesium or sulfur! The only real way to know if your soil is lacking magnesium or sulfur is to test your soil. Here are 3 simple DIY soil tests. (Or, there are soil tests provided by your cooperative extension.) If you add Epsom salts to soil that already has sufficient magnesium, this can harm plants and contaminate soil.
- In addition, spraying Epsom salt solutions on plant leaves can also cause leaf scorch. Excess magnesium can also increase mineral contamination in water that percolates through soil. Remember that Epsom salt is a highly soluble chemical. When you use Epsom salts on plants, it can it will leach out of your soil fast, running into and polluting ponds and streams. The best practice is to avoid adding any extra chemicals to your soil—even things that seem ‘safe’— because you can easily do more harm than good.
Alternatives to Epsom Salt
Before heading to the drug store for some Epsom salts, get an OMRI-certified agricultural-grade magnesium sulfate or look for a slow-release form of magnesium that will have longer lasting effects such as magnesium-enriched biochar or kieserite. If your soil is acidic, dolomitic limestone will raise the pH and add magnesium.
Save the Epsom salts for soothing your tired aching body after a day in the garden!
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I tired Epsom salts to an outdoor veggie garden—NOPE. I have a greenhouse now and there are so many GREAT soil amendments now that work a great deal better..
Quite a few years ago I was growing a few tomatoes in containers, one of them got blossom end rot. I was talking to family about it
and was told to try to put some Epsom Salts up under the plant and it would stop it. I was hesitant as I thought there must be salt of some kind in it, I did however do it and sure enough no more blossom end rot on the next tomatoes on that plant. Would I use it again, absolutely yes!
Epsoms Salts were discovered in a water-well in Epsom; England; at one time only Royalty could drink the well-water;
Interesting article. I'm mostly an indoor-plant person and an outdoor, container-plant gardener. For years, I've been using a mild solution (one tespoon per gallon of water) of Epson Salts to water my plants with none of these signs of harm to the plants. I only use this solution once a month at most, especially in winter and alternate with Schultz (liquid) 10-15-10 Plant Food Plus. I use Schultz or Miracle-Gro Liqua Feed more often in summer. Also my wellwater which I use for my plants is high in iron. My Jade Plants thrive and my other plants seem very content. I will keep these warnings in mind as I continue my routine. Thank you.
I my part of the world, the desert southwest, Miracle Grow is not as effective as it is in kinder soils. The additives we need in our depleted soils is that provided by FertiLome or Carl Pool.
I use epsom salt to treat the snow and ice on my porches. The grasses near the porches are greener and look healthier in the spring. Have used the salts for years without problem as a sprinkling along with compost. Doesn't seen to cause problems.
I have my doubts about the university study cited in this article to suggest Epsom salts are of no value to roses. What is true in the area where testing/study occurred might not be hold up in a different gardening/soil environment — of which there are MANY in the United States.
With Epsom salt, I can visibly see the difference in my roses in the form of more growth and healthier looking leaves. (I have also seen it do wonders for citrus trees.) As the old saying goes, however, "Your mileage may vary": Gardeners in other states may or may not notice similar results because their soil is higher quality to begin with. Not so where I live. I live near a seasonal lake that is covered in white residue when it dries out — presumably evidence of calcium/potassium abundance in the soil. The well water in the area is filled with so much iron, I have to filter it to drink it. The sandy soil in my area is presumably also very alkaline (can't grow a camellia or blueberry bush to save my life no matter how much I attempt acidify the soil).
To be perfectly honest, after relocating from a coastal zone to the High Desert (Zone 9), I have found Epsom salts more useful in a pinch than the County cooperative extension (would love to try soil testing but can't raise anyone on the phone who seems to know where to point me. Phone tag is about as good as it gets here in LA County. I've even tried writing to UC Davis and UC Riverside with no success).
The notion that Epsom salts may accumulate in such vast quantities to become an environmental pollutant seems amusing to say the least. It is one of the least processed substances one can apply to plants, compared to the many chemical-based fertilizers sold in garden centers. I have never heard of "magnesium runoff" spoiling water tables, whereas I have heard plenty about contamination tied to nitrates linked to agriculture, septic systems and the like (i.e. "blue baby syndrome").
In conclusion, just as it is possible to over- or under-apply a "balanced" fertilizer, it is possible to over- or under-use Epsom salt. Debate about whether it is harmful or helpful is about as useful as saying a balanced fertilizer is "beneficial" — without the caveat of how often or how much! It's a matter of common sense, really. In moderation it can't hurt — and if it helps one will observe the results soon enough.
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