Almost daily, I see a post in social media about using Epsom salt to cure all manner of plant problem. Planting a new plant; add Epsom salt to the planting hole. Are bugs your problem? Epsom salt will get rid of them. It also gets rid of diseases, and blemished on leaves. It makes tomatoes grow bigger, and produces a higher yield, with no Blossom End Rot. Roses are absolutely dependent on the stuff – you must put it in the planting hole every time.
If Epsom salt is such a miracle cure for plants, why is it that the scientific community does not know about it? Time to debunk this myth once and for all.
What is Epsom Salt?
Epsom salt is a very simple chemical consisting of magnesium, sulfate, and some water. The water is tied up in the crystalline structure of the chemical, and we can ignore it.
Magnesium is one of the nutrients plants need to grow. It is however, a minor nutrient which means plants don’t need very much of it.
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.
Epsom Salt Fertilizer
Epsom salt does work as a specific fertilizer. If your soil is deficient of magnesium or sulfur, it will add these nutrients to the soil. As far as garden soil goes neither of these nutrients is usually deficient. If you are adding any kind of organic material or organic mulch to the soil, your soil will likely have enough of both magnesium and sulfur.
Sandy soil and acidic soil may have a deficiency of magnesium (ref 1).
It should not be added to soil unless a soil test shows you that you need to add more. If you need only sulfur and not magnesium, then horticultural sulfur is a much better product to use.
Just to be clear – the NPK numbers for Epsom salts is 0-0-0.
Video Version
This is the video version of this post.
Magnesium Deficiency in Plants
What about a plant that shows a magnesium deficiency? First off, it is hard to identify a nutrient deficiency by looking at plants – that is another myth. But lets say you are sure your plant has a magnesium deficiency. It seems to make sense to add Epsom salt to the soil – right? Not necessarily.
High levels of phosphorus in the soil prevents plants from absorbing magnesium even though there might be lots in the soil. The solution in this case is to either reduce the phosphorus level, which is hard to do quickly. In this case ading Epsom salt will not work. Soil chemistry is complicated – don’t mess with it unless you know what you are doing.
Does Epsom Salt Control Pests
Current research has found no evidence that it controls pests. It does not kill insects or grubs, nor does it repel slugs and rabbits. It is completely useless for pest control
Does Epsom Salt Control Diseases
There is no clear evidence that any disease is controlled by Epsom salt.
Does Epsom Salt Make Plants Grow Better?
Epsom salt is not a miracle product. Provided that your soil has enough magnesium it will not make plants grow better, nor will it make more flowers, or make tomatoes grow bigger.
Magnesium is part of the chlorophyll molecule and vital for plants to grow. If it is missing in the soil, plants won’t grow as well, and adding magnesium to the soil will help. But that is only true if you have a deficiency.
What About Roses?
Epsom salt is recommended most frequently for roses. You put some in the planting hole and you feed with it yearly. Is this advice scientifically sound?
A review of the literature found no scientific evidence that roses need more magnesium than other plants. The Rose Society of America (ref 2) does not recommend Epsom salts for the ‘casual rose grower’, but does recommend it if you are a ‘rose specialist’. Why would the depth of your interest in roses affect which fertilizer is required?? That makes no sense.
The marriage of roses and Epsom salt has been with us a long time, and bad habits are hard to break.
I grow some roses. I’ve never added Epsom salts to any plant in the garden and my roses grow just fine.
Preventing Blossom End Rot in Tomatoes
Epsom salt is regularly recommend for tomatoes to prevent blossom end rot. I have discussed this in Blossom End Rot. Blossom End Rot is a calcium deficiency in the fruit – not a magnesium deficiency. With respect to Blossom End Rot, reference 3 says “Avoid excessive potassium or magnesium fertilization as these nutrients will compete with calcium for uptake by the plants. Epsom salts is an example of a magnesium source, so do not apply to soil unless a recent soil report indicates a magnesium deficiency.”
Adding magnesium can cause Blossom End Rot – it is not fixing the problem.
Should You Use Epsom Salts?
This is real simple – only if your soil test shows that you have a magnesium deficiency.
References:
1) Miracle, myth…or marketing, Epsom salts; https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/epsom-salts.pdf
2) American Rose Society: http://www.rose.org/rose-care-articles/fertilizers-when-and-how/
3) Blossom End Rot of Tomato – an Update: http://www.clemson.edu/extension/hgic/hot_topics/2009/08blossom_end_rot.html
4) Photo Source: Stacie Biehler
Would there be any interaction issues with Epsom Salt and Chelated Iron? I am growing Blueberries in a somewhat sandy and not quite as acidic as it should be soil. I have been working to correct the pH of the soil, and have been using the chelated iron to supplement because the soil is not quite as acidic as the plants would prefer. However, in using a troubleshooter I found online, I am told that the plants are deficient in Magnesium, so I am thinking about giving Epsom Salt a try, just wondering if there could be any issues to consider.
I don’t think so. But I don’t understand why you are using chelated iron to acidify the soil. Just use some sulfur.
I am using sulfur to bring the pH down, the chelated Iron is only because the soil is not as acidic as it should be. My understanding is that if blueberries do not have an acidic soil they become Iron deficient, chelated iron can be used in watering and/or foliar spray to temporarily correct this deficiency.
Also, in the last few days, the interveinal reddening of my blueberry leaves has dissipated. While the trouble shooting guide said that was a sign of Magnesium deficiency, it did not say (which I found at a different source) that it could also be caused by cold temperatures. While I am sure that a little Epsom Salt would not have hurt the plants, I am glad to have found out the real cause of my reddening leaves this time.
Thanks for your help anyway, thanks for all the info!
You can use and acidifying fertilizer, which will have ammonium salts.
Humm, Hi Robert!
I do not have a degree in biochem, nor chem. I do have a degree in Ornamental Horticulture. Everything you suggest is exactly what I learned at Cal Poly Pomona. I also learned less is more when it comes to using fertilizers.
I recently started working at a garden center in Colorado.
Oh boy! The things I hear people swear by!
Yesterday I heard the Epsom Salt one.
I almost started laughing at the customer.
I chose to act ignorant and AMAZED! A simple home remedy could actually produce fantastical results! WOW! Where have I been.
If I remember correctly I believe it can take many years for the magnesium to become available to the plants.
I even recently had a “Geologist ” tell me adding lime to alkaline soils was needed, I thought it was the other way around, in fact it is! Lime is added to acidic soils!
But hey! What do I know!
I have been gardening, observing, planting, killing plants since I was 9. I am a blue ribbon winner when it comes to garden plant shows, but hey, I will just keep on acting ignorant and “Amazed” every time I hear a new fantastical garden “Miracle ” method!
The magnesium in Epsom slats will be available to plants almost immediately – as soon as it dissolves.
Robert you are coming across completely credible…and I am hearing a little frustration now as well. Trying to tell people the truth, and if that truth is a little bit different than their…knowledge… it seems as if there is an impermeable barrier. I’m up to my eyebrows in education and experience and amazingly, even degrees/experience/licenses…just don’t hold any water when people need to believe they way they do. To make any changes within their tenuous knowledge foundation would mean big housekeeping. You do so very well explaining and answering! Keep on being sorta frustrated a little irritated. These people have been coddled enough. To have the audacity to ARGUE with you (is a good thing once one has a decent and well earned foundation) when they are asking a question is terms for putting them in their place. Your knowledge is very well rounded, interconnected, small scale down to cellular level as well as being able to step back and explain the bigger picture. You are brilliant.
Thanks so much. We work at converting one person at a time.
Thanks for info on epsom salts. Will probably still use but sparingly. I know a ” scientific ” medical doctor who swears by it for his tomatoes. I do not want to block absorption of vital nutrients. Check your spell checker. In your opening you referred to ” all mannor “. It is all manner. Thanks, vicki
Thanks.
Hello Mr. Pavlis; not only am I concerned about the epson salt trend but even more so with NO TILL and NO FERTILIZER. Contacted the NO TILL dudes and even they acknowledge it is MINIMUM till not no till and no Fertilizer is so infuriating. Where are your other blogs or answers to these newbies who know nothing about the basics much less trying to change the basics…?
The university near hear has some no-till going back 25 years, and have records infiltration rates of over 20 in/hr in clay loam.
Whenever you disturb the soil you’re going to lose water and nitrogen. Mulch/compost is slow release and can be a great friend in the garden.
Thank you for the article. I commend you on your patience when dealing with people that choose witchcraft over science.
How about using epsom salt as a foliar. It is my understanding that because magnesium sulfate is so small, it can be absorbed through the leaves? Hokum?
It is absorbed, but that does not solve the problem of a lack of magnesium in the soil. Foliar feeding is a short term band aide – not a long term solution to a nutrient problem. It is a poor option for homeowners but does have some commercial applications for specific situations.
Hi, I searched the web to see if I or anyone else could find any scientific evidence to support the idea that an Epsom bath is good for the human body… And would you believe, there has been no studies or very loosely (unscientificly approached) arguments stating that it does. But who needs science when you can just bathe in it and see how you feel. And although the body may need magnesium and sulfate, I’m pretty sure that’s not the only reason. And I am well aware that we are two completely different organisms, but we both coexist with Epsom and water around us. I may be unscientific, but I find it easier to understand things through feeling.
P.S. “Scientific Evidence” may be also referred to as “Circumstantial Evidence,” because we know that to be true, we can assume that this is true.
Studies have shown that magnesium is not absorbed through the human skin. Unless you eat it – Epsom salts does not had magnesium to your body.
Re: “P.S. “Scientific Evidence” may be also referred to as “Circumstantial Evidence,” because we know that to be true, we can assume that this is true.” – that is not true.
I find Epsom Salt contains a little portion of arsenic. My question, do the plants uptake it and can it come to human body if it is vegetable or fruit when they are consumed ?…. thanks
Plants do absorb arsenic, and if you eat such plants, it will enter the body.
I doubt most Epsom salt has significant levels of arsenic; http://chemistry.stackexchange.com/questions/8079/epsom-salts-heavy-metal-contamination-myth
Poor Robert! I’m not sure if your trying to help people or if you just want to be right. No one has to scientifically prove it to you since we all reap rewards from Epsom salt, I especially do with indoor plants. The question is are you a scientist? And how much have you done to obtain your claim that it does nothing? It seems you may have searched the internet( which you said lies) and found no evidence either way? Nothing to prove or disprove since you say you found nothing. Just because science hasn’t got its test tubes out doesn’t mean it doesn’t work. Once upon a time there was no name for many illnesses!! Because it was not discovered yet or given a name, not because it didn’t exist beforehand. Even today people have unknown, not understood illness. Not everything can be scientifically understood. You can learn from the proof of beautiful plants that were not beautiful or happy before. Or you can buy a dying plant from a nursery and do some real science! take it home and test the soil etc etc leave it, water it, bla bla, then when your ready add the epsom salts, and you can begin to build evidence, retest the soil watch the plant for change. And I would welcome the scientific result, for science is about trying and testing. You may still not get an accurate result, because science in the world isn’t always accurate, it can try and help us to understand how things work but can never be literal( in my opinion). We are all scientists and our proof is our results. Sometimes it may be that the plant needed magnesium or maybe it didn’t natural salts also contains sodium, iron, calcium and potassium and more(mine states up to 84 minerals and trace elements). If your plant is suffering I think it is prob some type of deficiency and these natural salts could really be beneficial. Thanks.
One of the most common arguments people make, when their belief is not supported by science, is; ” But we don’t know everything”.
Science does not know everything, but the effect of Epsom salts has been tested a lot – we know enough to say that their is no known benefit except for a known nutrient deficiency.
Yes – I have degrees in chemistry and biochemistry.
Your other writings you say you have a “Back Ground” in chemistry and biochemistry. Can’t find info on your Degrees. Can you share a link?
B.Sc. in chemistry and M.Sc in biochemistry
Having read that you can’t over use Epsom Salts I used it rather liberally and now I am concerned, as I think I have over dosed my plants with Epsom Salts. I read if the plants get too much Epsom Salts they then can’t use the Iron properly and this is what I think my plants are now suffering from.
Any Comments please
Too much of anything is not good for the soil. If the plants are not growing well, get a soil test done.
The symptoms of excess magnesium “Excess magnesium has induced some toxicity symptoms like development of coppery color along the marginal veins at the initial stage. The mid rib region was also slightly affected. Extensive coppery color developed all over the leaf surface and defoliation of leaf occurred during the final staged of toxicity”
Thank you for your quick reply. I am very pleased to tell you that the plants have none of the symptoms you mention.
The leaves are yellow. I know it is not lack of nitrogen, as these were recently replanted, when I added the Epsom Salts. The plants are actually flowering too but I know there is a problem.
Living where I do, at the coast in Kenya it is nearly impossible to get the soil tested.
I have grown hibiscus for many years without any problems.
Thank you for your help.
Marion
Yellow leaves could also be due to nitrogen or iron deficiency
I HAVE BEEN USING EPSOM SALTS IN MY GARDEN FOR DECADES AND FIND IT EXCELLENT.
I USE IT WHEN PLANTING BULBS, SEEDS, SEEDLINGS, SHRUBS,
VEGETABLES, GROUND COVERS, TREES, ROSE TREES ETC.
NOTHING AS GOOD AS EPSOM SALTS IN THE HOLE WHEN TRANSPLANTING TREES OR SHRUBS EVEN IN THE SUMMER.
THE REASON BEING THAT EPSOM SALTS MINIMISES DEHYDRATION AND THERE IS NO SHOCK WHEN TRANSPLANTING BIG ITEMS.
I EVEN KNOW OF MY DOMESTIC YEARS AGO WHO WHEN ARRIVING HOME AFTER WORK DECIDED TO IGNORE THE APPROACHING THUNDERSTORM SINCE SHE WANTED TO HANG OUT HER WASHING.
NO SOONER HAD SHE STARTED HANGING OUT HER WET WASHING THEN THE LIGHTNING STRUCK THE END OF THE LINE.
SHE HAD A MASSIVE SHOCK AND FELT WEAK AND NASEAOUS.
FORTUNATELY HER NEIGHBOUR HAD SEEN WHAT HAPPENED AND CALLED HER TO HER HOME.
SHE GAVE JEANETTE A GLASS OF WATER INTO WHICH SHE HAD STIRRED A TEASPOON OF EPSOM SALTS (MAGNESIUM SULPHATE) AND THAT WAS ALL IT TOOK TO MAKE HER FEEL BETTER AFTER A SHORT WHILE.
LONG LIVE EPSOM SALTS AND THOSE WHO ARE ABLE TO SEE THE BIGGER PICTURE!!
WE KNOW SOMETHING WHICH OTHERS REFUSE TO BELIEVE,
AND THAT IS JUST TOO BAD!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ALSO KILLS SNAILS. AN EXCELLENT FOLIAR FEED AND I USE IT WITH GARLIC, BI-CARB, ONION, DISHWASHING LIQUID DILUTED IN WATER AS A SPRAY FOR ROSES.
NO POISONS OF ANY KIND IN MY GARDEN…
You say “NO POISONS OF ANY KIND IN MY GARDEN”, but too much magnesium can become toxic!
All of your other comments are not supported by science.
As I said I have been gardening for decades and find Epsom salts excellent!!!
My gardener and I don’t use it by the teaspoon full we use it by handfulls and a number of times a year.
This has been in 4 different large gardens in South Africa; Port Elizabeth in the Eastern Cape and George in the Southern Cape.
I also use it especially for Azaleas, Brunfelsias, Camellias, Ferns,
Hydrangeas. My neighbour next door uses it to feed her Gardenia
and it is recommended also for Proteas and Citrus fruit trees.
My fiance also uses it every time he plants us tomato seedlings.
(He taught me something I did not know and that is to take cuttings of tomato plants, put them in a cup with some water and in a few days they have developed roots. I add a pinch of Epsom salts and then it goes quicker.)
Epsom salts builds strong root systems and cell walls of leaves and stems. It makes tomatoes sweeter too. Fruit trees and vegetables bare more abundantly and any plant which bears flowers, flowers far, far better.
(WHEN I PLANT FLOWER BULBS I EVEN PLANT THOSE WHO WERE SUPPOSED TO HAVE PASSED THEIR EXPIRY DATE BY YEARS; AND THE SAME WITH SEEDS. WATER WELL AND FREQUENTLY AND YOU WILL SEE RESULTS!!
BE HAPPY; WE ALL LEARN FROM EACH OTHER; AND TODAY YOU HAVE LEARNT FROM ME THAT EPSOM SALTS IS NOT TOXIC!!
Just because you use it does NOT mean it works. It might work for you because you have very low magnesium levels, but most of your comments are not correct.
If you want to convince me – provide some references for your claims.
I disagree withe gentle. An who claims too much magnesium is toxic
http://scialert.net/fulltext/?doi=rjphyto.2010.67.77&org=10
I agree, epsom salt is the best fertilizer I have ever used. Was kind of leary when I first tried it 2 years ago. First tried it on my peach tree that looked like it was dying. I noticed about 2 weeks later how much it had grown. The tree is now growing great. I use it on all my trees and veggies also. Works great.
Epsom salts will help plants when they are deficient in magnesium. It is not a fertilizer by most definitions since it is missing the 3 main nutrients NPK.
The are something like 14 essential plant nutrients. N, P, K, are macros, Mg, Ca, and S are quasi-macros. Cl, Fe, Mn, Mo, Ni, Cu, and B. All of these except Cl, and Ni can be in a fertilizer.
Sulfur is actually pretty important for the uptake and utilization of Nitrogen, and many plants will show a positive response when more sulfur is available. Magnesium sulfate like Gypsum (Calcium sulfate) can correct sodic soil conditions. (Though the later is cheaper)
Anyways, there are reasons it works, but it’s certainly better to understand what the problem might be before throwing the folk remedy at it.
Statements such as “many plants will show a positive response when more sulfur is available” are only true if the soil has a deficiency of sulfur.