Does Epsom Salt Benefit Tomatoes, Roses, and Garden Plants?
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Some gardeners swear by Epsom salts as a gardening hack. We’re here to tell you that Epsom salts are good for neither plants such as tomatoes or roses—nor the soil. Yes, it’s one of those gardening myths. Learn more—and let’s talk about 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-all? Can Epsom salts be harmful? Let’s separate fact from fiction.
What Is Epsom Salt?
Epsom salt is the chemical magnesium sulfate (MgSO4)—which means both magnesium (about 10%) and sulfur (about 13%).
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- 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. Adding 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, its 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 use 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. 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 the soil.
- In addition, spraying Epsom salt solutions on plant leaves can also cause leaf scorch. Excess magnesium can also increase mineral contamination in the water that percolates through the soil. Remember that Epsom salt is a highly soluble chemical. When you use Epsom salts on plants, they 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 in the Garden
Before heading to the drug store for some Epsom salts, 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 to soothe your tired, aching body after a day in the garden!
Read more about gardening myths!
Have you ever used Epsom salt in the garden? What was your experience?
Robin Sweetser
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I used Epsom salts, diluted as recommended for yellowing camellia leaves, & also on magnolias, rhododendrons & roses.I have clay based soil, gets dry. I was pleased to see the camellias etc gradually green up ( acid plant feed hasn't helped) & my pink magnolia Stellata has produced the deepest pink ever this Spring.It was very pale pink before. I think it's worth stressing that E salts needs to be properly diluted as advised by pro gardeners (in UK), & not used as dry powder.
Never heard of anyone treating blossom end rot with Epsom salt. It's true over doing magnesium will lock out calcium as well as potassium, but same can be said with calcium locking out potassium, magnesium, phosphorus, manganese, and iron , and too heavy with potassium locks out magnesium, calcium, and zinc. The competent gardener will have read the application rates on the packaging for the given crop. He or She would have more than likely browsed the gardening section (If savvy enough may even googled a few key descriptive words) and at some point saw the calcium nitrate. Even with a vague description "Cures blossom end rot in tomatoes!" Id bet most cultivators worth their epsom "salt" could string the key words together and draw a connection to their gardening woes.
Thank you so much Robin for writing this article. As a horticulturist (retired) I have been telling people for years to stop using Epsom Salts! And we still see so many write ups suggesting its use. Your article will reach many people and hopefully change their minds about using it. It's not good for the plants and it's harmful to our previous water supply! Thanks again!
Why do you say Epsom Salt is a myth and recommend against it,
Then go on to recommend an OMRI certified magnesium/Sulfate which is the same thing in composition?
I've been using Epsom salt for years and it's been very beneficial why do you say it's not
Thank you for bringing this to our attention. We have revised the text.
In my north Alabama raised bed garden I use epsom salt on almost all of my vegetable plants. They are greener and healthier and have good production. On my tomatoes plants I also put a bit of dry milk powder in the planting hole which gives them calcium. This year I am trying to grow squash as a climbing vine to save room and try to miss the vine borer, I also sprinkle cinnamon powder around my plants to ward off fungus and cayenne pepper to ward off animals..
That’s wonderful that you are having success using epsom salts in your garden. Thanks for sharing!
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!
