Epsom Salt for plants is a garden myth I have wanted to debunk for a long time. It is not the wildly beneficial fertilizer everyone claims but it can cause much more harm than good. This article will explain why you should not use Epsom Salt in your home garden!
Epsom Salt for plants has been touted as a cure all for many things in the garden. Pinterest is rife with claims, some from so called ‘reliable’ garden sites. Or at least popular ones.
But the truth is these claims are all ‘anecdotal’ at best and harmful to the earth at the worst. Especially if everyone jumps on the Epsom Salt bandwagon.
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Lets start with…..
What is Epsom Salt?
Here is the definition:
Magnesium sulfate is an inorganic salt (chemical compound) containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate sulfate mineral epsomite (MgSO4·7H2O), commonly called Epsom salt.
I will simplify it.
Epsom salt is a very simple chemical consisting of magnesium, sulfate, and some water.
Though magnesium is one of the nutrients plants need to grow, it is a minor nutrient which means plants don’t need very much of it. And most soils have plenty of magnesium in it especially in the mid-west and western states.
Sulfate consists of sulfur and oxygen. Plants can absorb sulfate directly from the soil and use the sulfur molecule. It too is a minor nutrient for plants.
Most composts and other fertilizers contain more than enough magnesium if you use them in your garden as top dressing or amendments. Adding more in the form of Epsom salts is counter productive.
Epsom salts for plants was never intended.
Does Epsom salt cure blossom end rot?
Even though many claim that adding Epsom salt to your soil prevents blossom end rot you may be surprised to learn that instead it may be a contributor to it.
How’s that? The main cause of Blossom End Rot is the lack of calcium uptake by the plant not the lack of magnesium.
Here is a wonderful quote from the Michigan State University extension…
Blossom-end rot is caused by insufficient calcium in the tissue of the tomato. Calcium is taken up into the plant through the roots, however, it settles in one part of the plant. This means that the rot can occur even when there is an ample supply of calcium in the soil, stems or leaves. Actively growing parts of the plant such as developing tomatoes must have a continuous supply of calcium to prevent these spots from developing.
The conditions that cause blossom-end rot are closely linked to inconsistent soil moisture throughout the growing season. Since calcium is only moved into the plant with an ample moisture supply, when drought occurs the fruit continues to develop but will be affected by a calcium deficiency.
Rapid early growth of the plants can cause the rot because the calcium is needed by the tomatoes when they are actively growing and the plants may not be able to take up sufficient calcium quickly enough through the roots. (end of quote)
Adding Epsom salt to the soil may create more rot since magnesium and calcium ions compete for uptake into the plant. The more magnesium in the soil, the less chance that calcium will be absorbed.
Again, calcium and magnesium compete and if one is out of balance then it effects the plant and fruit.
How can you prevent blossom end rot? Easy….
Mulch and regular irrigation. Adding mulch and having a regular source of watering (like a drip or soaker type hose set for deep watering on a regular basis) keeps the soil from the extreme cycles of dry and moist.
Over fertilization can also cause BER, especially with ammoniacal nitrogen fertilizers (ammonium nitrate and most complete fertilizers such as 10–10–10). Ammonium competes with calcium for uptake.
Tomato vines should be green but not lush. Lush tomato plants are more likely to suffer rot since actively growing leaves take calcium from the vine before the fruits get it. I can attest to this being true.
This year one of my tomato beds was partially filled with chicken litter (notoriously high nitrogen) then topped with a compost soil mix. The tomatoes growing in this bed were so lush, they were like jungle plants. Judicious pruning helped but these were the only tomatoes in my garden that suffered with blossom end rot despite even watering. Note to self, avoid high nitrogen amendments in future tomato beds.
Another note, sometimes, soils that are too acid prevent plants from using magnesium efficiently. The easiest and long-term remedy for that is to add organic matter. Garden limestone is another.
Epsom salt cures chlorosis
Nope. It is true that magnesium is a physical part of the chlorophyll molecule. But since most soils are not deficient in magnesium then to treat chlorosis with additional magnesium (Espsom salts) is useless.
Most of the time chlorisis is an iron deficiency in the soil and not magnesium. Using an Iron supplement in your garden is best. If you go the route of adding magnesium instead of iron you only increase the problem.
Epsom Salt improves seed germination
Seeds need no extra nutrition and contain enough essential minerals to begin root growth and shoots on a mere paper towel.
Related: How to Start Seeds
Adding Epsom salt doesn’t do a thing and can actually restrict healthy growth.
Epsom Salt for houseplants
Houseplants aren’t as fortunate as our garden plants in that they do build up excessive nutrients in the confinement of pots.
If you feed your houseplants a balanced fertilizer with all the necessary macro and micro nutrients adding more magnesium and sulfur will only result in a build up. (it doesn’t leach away)
This will cause damage to leaves and roots.
Adding Epsom salt produces more flowers
Flower production does not rely on magnesium or sulphur.
Flower production is more dependent on the optimal temperatures and watering. Well amended soil is first and foremost then comes a good organic fertilizer to promote blooming.
Related: Get more blooms on your Flowers
Epsom salt deters pests
Not even close. One claim I read was that sprinkling Epsom salt around your garbage cans will keep raccoons away as they don’t like the taste of it. Sorry, this does not work in the least. Tried it, big fat fail!
What about slugs?
Again, EP did not do the job. Some claim that slugs and snails provide a benefit in the garden so better yet try to keep slugs and snails in check with some of the methods over at AllAboutSlugs.com.
But most importantly, it isn’t what Epsom salt doesn’t do but what it does!
Read on….this is the part I really want you to read…
What harm can it cause in the garden?
So we have learned that magnesium is not usually deficient in soil but what harm can it do in using it? So many gardeners swear by it!
Immediate dangers is the imbalance of nutrients in the soil. Which in itself is contrary to what we as gardeners all want. Good balanced soil is your best garden recipe for success.
Excessive levels of magnesium sulphate can cause salt injury to plants. Unnecessary use of Epsom salt will not result in better plant growth but can actually make growth worse. I received one comment about Epsom Salt not being sodium. The term salt is used in chemistry and does not always pertain to sodium being involved. In science a salt injury is equated to a negative effect of chemicals. As stated before, Epsom Salt is a chemical compound.
Overuse of magnesium sulfate has been linked to reduced root colonization of beneficial microbes such as nitrogen-fixing bacteria. Also excessive amounts of soil magnesium can release aluminum from the soil, making this toxic metal available to plants and aquatic systems. (and if we eat those plants it is a possible problem for us)
Did you know that to avoid magnesium toxicity, the calcium content of the soil needs to be at least 10 times higher than the magnesium. So adding Epsom salt alone can cause that imbalance and create a toxic environment for the plants trying to grow.
Good thing is Epsom salt is highly soluble so it doesn’t persist in the soil and build up.
But is that really a good thing?
Just think about that for a minute. Highly soluble means it washes away easily.
What many seem to ignore or not think about is that the excess ends up somewhere, most often as a pollutant or contaminant in the environment especially waterways.
Since additional magnesium is rarely needed (get a soil test done) why potentially bring more harm to our already struggling environment?
Why do people use Epsom salt for plants instead of safer fertilizers and other well documented methods?
The urge to use common household products as garden fertilizers and pesticides is compelling for many gardeners who want simple, cheap and what may seem to be harmless.
For some reason we feel if we can use it and or consume it then it must be safe to put in the garden.
But before you use any chemical in your garden or landscape you should ask yourself
• Is it really necessary?
• Can it cause damage?
The science behind any use of Epsom salts in gardening is only applicable in intensive crop production where it is known to be deficient in the soil.
Why I don’t use it in my garden
Main reason…It isn’t necessary or beneficial.
Therefore it is highly irresponsible to advise anyone to use Epsom salts for plants in the garden, on houseplants or in the landscape without regard of what it can harm in the environment.
If your garden does not need the addition of magnesium sulphate then using Espsom salts will only create problems not enhance your gardening efforts.
Final thoughts..None of these so called miracle recipes found on Pinterest or the internet are based on science, and their use could create soil nutrient imbalances and cause substantial injury to plants and/or the environment.
Stop the Insanity!
Happy Gardening friends,
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