Fertilizer Supplements: Is Epsom Salt Good for Orchids?

I once thought that fertilizing with a balanced fertilizer, 20-20-20 year-round was sufficient. Then I read about not using an orchid fertilizer with urea nitrogen in it. Then the question came up about using Epsom Salt as and orchid fertilizer. After all, what does Epsom salt do for orchids?

Epsom salt is extremely beneficial for your orchid’s maintenance and nutrition. Not only does it help with the production of chlorophyll, Epsom salt aids in cell construction, proper hydration, and flushes out the orchid from salt residue. Epsom Salt will make the blooms larger and the leaves more vivid, causing no harm to your orchid.

To use Epsom salt on orchids, mix one tablespoon in 4 liters (1 gallon) of water. Use this mixture to water your orchids 3 to 4 times a year. You can use it as a foliar mist, but incorporating Epsom salt into your watering regime is easier.

With the use of Epsom salt, there have been many questions about its use and exactly what it does.

This article will explain how and why Epsom Salt will make your orchid more beautiful and healthier than ever. Along with Epsom Salt, I’ve included iron and calcium in the article, since many products on the market also include those. Yet, Epsom Salt does influence how your orchid absorbs iron, calcium, and aluminum. So it’s not a mistake these elements are also included in this article.

Applying orchid fertilizer and orchid supplements are not a complicated subjects, and the more you immerse yourself in the different possibilities, the more fascinating it gets. Well, at least for me…and I’m not good at chemistry. So if I can do it, I’m positive you can too.

In this Video, I explain Epsom Salt and Orchids.

You might be wondering where Epsom salt got its name. It was discovered in the well water of Epsom, England, and soon became extremely popular. At that time, the benefits were medicinal, as the claims of bathing or soaking in Epsom Salt were beneficial in many areas. Since medicine isn’t my area either, I’ll just list the claims, but I don’t certify that they are 100% what they say (they could be, I just don’t know).

For medicinal purposes, bathing or soaking in Epsom salt is said to reduce blood pressure, helps relieve headaches, and increases serotonin. There are not many studies to say that your skin absorbs the magnesium in Epsom Salt just by soaking in it. 

Epsom salt is not exactly a salt. That is what stumped me for the longest time. It’s just a mineral composite of Magnesium and Sulfate.

According to one producer of Epsom salt’s homepage, “Magnesium plays a number of roles in the body including regulating the activity of over 325 enzymes, reducing inflammation, helping muscle and nerve function, and helping to prevent artery hardening. Sulfates help improve the absorption of nutrients, flush toxins, and help ease migraine headaches.”

 This is very controversial and not the reason why you are reading this article, so let’s get to the point.

Epsom Salt? I thought adding salt was bad for the orchid.

Don’t ever, I repeat DON’T EVER add salt to your orchid. Epsom Salt is not table salt. Salt from the kitchen table will destroy your orchid and burn the roots. Table salt is Sodium Chloride (NaCl) and Epsom Salt is epsomite, which broken down is magnesium (Mg), sulfur (S) and oxygen (O).

I had to add this little blurb because I had learned as a very young girl that one way the villains would take over enemy lands and make sure those fertile lands would never produce crops again, was to put salt on the fields. This led to fields that wouldn’t produce any more crops—an evil way to humiliated and conquer your enemies with starvation. So, when I heard of adding salt to orchids, my first reaction was no way! That’s why I’m emphatic to say that Epsom salt is not table salt.

How Does Epsom Salt Influence Your Orchid’s Growth?

Epsom salt is a epsomite, which broken down is magnesium (Mg), sulfur (S) and oxygen (O). These are all nutrients that your orchid needs. Most orchid fertilizers are only sold with NPK (nitrogen, phosphorus, and potassium), and if you only use them, your orchid will display other micronutrient deficiencies in time. One of the deficiencies is magnesium.  

A good source of magnesium for your orchid is Epsom Salt, since it is made from Magnesium Sulfate.

According to the MGSu Technical Evaluation Report compiled by ICF International for the USDA National Organic Program, published in 2011 by USDA (Source)  Epsom Salt is useful in plants mainly because of the magnesium, since it’s about 10 percent magnesium and 13 percent sulfur.

Magnesium is extremely vital to produce chlorophyll, as is iron. If you water too heavily, magnesium will be washed out of the potting medium, so there hardly is any build-up from “overdosing” in magnesium. On the other hand, if you don’t flush your orchid, the magnesium will build up. As everything in life, it’s a fine line…

Magnesium is absorbed through your orchid’s roots and is transported through the entire orchid, unlike some of the other nutrients and minerals. I’ll talk about those below. Since magnesium flows freely through your orchid, if there is a deficiency, the orchid will try to save the newer leaves in detriment to the older leaves. The older leaves will start to turn purple or have splotches of green throughout the leaves.

In the same article cited above, the authors mentioned that “…magnesium is critical in biochemical and physiological plant processes, including photosynthetic carbon dioxide fixation, proteinsynthesis, chlorophyll formation, partitioning and utilization of photoassimilates, photophosphorylation (including ATP formation in chloroplasts), loading of sucrose in the phloem, photo-oxidation in leaf tissues, and the generation of reactive oxygen species.”

Your orchid will use magnesium mainly to conduct the process of photosynthesis. This means that most of the magnesium will be stored in the orchid’s leaves, where the light that reaches the leaves will be converted into chemical energy. Higher light orchids will need more magnesium to conduct these processes, and when magnesium isn’t present (or present in very low doses) the leaves will have a hard time producing energy to thrive. 

If your orchid has magnesium deficiency, it will present small red dots on the leaves, which is due to interveinal chlorosis—all curable with Epsom Salt. You can read this article I wrote if you have black or red dots and aren’t sure what they are, but aren’t convinced it’s a lack of Epsom salt.

Does Epsom Salt Increase Chlorophyll In My Orchid?

Since Epsom salt aids directly in photosynthesis in your orchid(due to the high magnesium present), some people can make the mistake of reading into this correlation that magnesium creates more chlorophyll. The logic is that if you add Epsom Salt to your orchid, it will automatically increase the number of chlorophyll in your orchid’s leaves.

This is not true.

According to Linda Chalker-Scott, Ph.D. a Master Gardener and WSU editor, “Magnesium is a physical part of the chlorophyll molecule. A deficiency of magnesium will cause a corresponding reduction in chlorophyll production (leading to leaf chlorosis often used as an indicator of magnesium deficiency.) Epsom salts added to adequately-fertilized plants will not increase chlorophyll production for that species.” (Source)

Keep in mind that Epsom Salt aids in the healthy structure of chlorophyll, but it does not increase the production of chlorophyll.

What Chemicals Does Epsom Salt Regulate in My Orchid?

Magnesium isn’t the only chemical that Epsom Salt helps regulate. It also regulates aluminum, iron, and calcium (in their own distinct ways). Please note that these chemicals are not present in Epsom Salt, but Epsom Salt helps the absorption (or depletion) of these nutrients when they are added at a later date.

How your orchid will react to the absorption of these chemicals will depend highly on your orchid’s potting media and what genus and species your orchid is. It’s not right to assume that Epsom salt will automatically increase or regulate these three items with one application, nor will all orchids react to these chemicals at the same rate or in the same manner. It is safe to acknowledge that the orchid will have a positive effect when Epsom salt is used, even if slightly.

According to the article “Understanding Soil Fertility” published by Penn State Extension in 2011, “Plant nutrient availability directly relates to soil pH. Calcium, magnesium, manganese, copper, zinc, iron, and boron are available to plants when the soil pH is 6.0 to 6.7.

Low pH levels also tie up some calcium and phosphorus, reducing their availability. In addition, magnesium and calcium deficiencies may occur in soils with excessive potassium levels. Excessive soil potassium competes for and reduces the uptake of calcium and magnesium by plants. (Source) Too much potassium in your potting media means that even if you apply a calcium supplement, like Cal Mag, your orchid can’t absorb it. Epsom salt is a way to reduce the potassium in your orchid potting media, since it flushes out the chemicals.

Even though the article I cited above was aimed at flowers that are planted in soil (and some orchids are—terrestrial orchids), most orchids that are sold on the market are epiphytes. This means that your soil will not be garden soil, but orchid bark, sphagnum moss, and other material that is more appropriate to orchids.

For a more comprehensive article on what you can use as potting media, please refer to this article that I wrote. This doesn’t invalidate the article above because these problems are still present in orchid media. The way they affect your will change, but in essence, they will still be present.

Epsom salt helps regulate these chemicals in your orchid’s potting media, meaning that it will reduce the potassium if those levels are high. Once you reduce the potassium, your orchid will be able to absorb more calcium and phosphorus. It’s not only the calcium, but a repertoire of many, many chemicals. Let’s look at a few.

Orchids and Aluminum

How does Epsom Salt enhance aluminum absorption in your orchid? It doesn’t. That’s right. In fact, what Epsom salt does is keep the aluminum toxicity rates low, bringing down that high level of aluminum that can hurt your orchid. Magnesium will interact with the orchid’s roots to release organic acid anions. These anions will chelate the toxic aluminum ions, transforming them into components that are not toxic to your orchid. 

If you have high rates of aluminum in your orchid’s potting media, then Epsom Salt will be the best way to reduce those values.

 It is almost impossible to detect an aluminum toxicity while the orchid is in the pot because this kind of high aluminum presence affects root growth. Aluminum toxicity stunts the roots, making them small, crumpled, and the very ends of the root tips will be browned or unnaturally rounded off. (Source)

If your orchid has beautiful long roots and the overflow from the pot, being more of a “problem” then not, then your orchid is not at risk. But let’s say that one year you notice your orchid just stopped developing these long, luscious, plump roots, and every root tip that once was green, is not stunted, short, and brown.

If it wasn’t mechanical damage, done by household pets or your hands, then it could be aluminum toxicity in your orchid’s potting media. If it is, you could notice that the high levels of aluminum will bring your pH level down to a drastic 5, instead of that beautiful normal level of 6.3 to 7.0.

Epsom Salt helps regulate this, but I also advise a repot because Epsom salt also brings the pH down even lower. Epsom salt will work on the magnesium, but the negative side is that the pH in your orchid media will drop a bit too. Also, I’ve never been able to bring up an orchid’s pH without a repot. I’ve seen it done, but I guess I’m not that good at it.

Numerous orchid growers have used Epsom Salt in between watering and the overall consensus was that the leaves were bigger, brighter, more luscious, and the blossoms were noticeably superior.

What Does Iron Do for Orchids?

What does iron do for orchids and how does Epsom salt interact with iron? Iron does not aid the plant specifically, but it helps produce chlorophyll, just as magnesium does. A deficiency in iron will negatively influence in how much chlorophyll will be created, and induce what we call chlorosis. Without chlorophyll, your orchid cannot take the light it is receiving and transform that into energy.

Chlorosis is not only caused by lack of iron. If you are overwatering and have been for some time, root rot will set in, and this also causes chlorosis. Before you add more iron to your watering schedule, make sure that the roots are in good condition and capable of absorbing the iron.

How Does Epsom Salt Interact with Iron?

Here is where most articles bypass the entire Epsom Salt, just focusing on magnesium and forgetting about the sulfur. There is more sulfur in Epsom Salt than there is in magnesium. If you try to find an article that has a correlation between magnesium and iron, there aren’t any. At least I couldn’t find any. But there are numerous articles explaining the relationship between sulfur and iron, and that is what I want to focus on.

According to Frontiers in Plant Science, in the article “Interaction Between Sulfur and Iron in Plants”, published in 2021 by Stefania Astolfi et all, (Source) “plant capability to take up and accumulate Fe [iron] strongly depends on S [sulfur] availability in the growth medium in both monocots and dicot plants.”

Even though “indeed, it remains a challenge to determine how the interplay between S and Fe is regulated and how plants are able to sense environmental nutrient fluctuations and then to adapt their uptake, translocation, assimilation, and signaling,” the relationship is very visible and relatable.

Iron deficiency in plants (and orchids too, of course) will show up as a lack in electron transfer, difficulty in plant respiration cycles, and photosynthesis. These are hard to identify from just looking at the orchid, but inside the leaves, the cell structures are suffering. “Iron deficiency provokes serious imbalances in the ultra-structure and functionality of chloroplasts, with 90% of Fe [iron] present in a leaf localized in the chloroplasts”. Your orchid leaf will start to yellow and lose its firmness.

You might be wondering, since there is so much iron in the earth, (Iron is the fourth largest or most abundant chemical in earth’s crust) then why should my orchid have a limitation or deficiency? This is because the form that iron is available in the soil doesn’t get absorbed by plants, especially orchids. It must be transformed by several chemical reactions so that it changes into a compound that is available to it.

Sulfur is the key element in this change. The more sulfur your potting media has, the better it works with iron to change the chemical formula into something your orchid likes. The more alkaline (higher pH) your potting media is, the more probable it is that your orchid is suffering from iron deficiency.

Epsom salt not only provides the sulfur to transform iron into a chemical compound the orchid can take up, but it also lowers the pH of your potting media, making iron more accessible to your orchid’s roots.

What Does Calcium Do for Your Orchid?

Calcium is a macro-mineral and extremely important for your orchid. Your city’s water supply usually adds a small percentage of calcium to the water already.

Calcium enters the orchid through the roots, and travels up toward the stem to where it is distributed through the xylem. This vascular system is not always fluctuating, and once the calcium stays where it needs to be, it doesn’t move throughout the plant (like our blood would move through the veins and arteries.)

Calcium has several benefits to your orchid. First, it will maintain healthy cell structure by neutralizing unwanted acidic components.

This means that once the calcium is in place, it isn’t supplied to places that don’t have it. That is why newer leaves can suffer from lack of calcium, while older leaves be fine. It’s common that you’ll first notice the calcium deficiency in orchids in newer leaves.

A sign your plant is not getting enough Calcium is when the tips of newer leaves start to turn yellow. The roots will be sprouting by the millions, but they don’t grow very long, as the lack of calcium will stunt growth.

If your pseudobulbs or leaves look smaller than the previous ones, then a good rule of thumb is that either they aren’t getting enough water or they are lacking calcium.

How Does Epsom Salt Interact with Calcium?

There is no calcium in Epsom Salt. Just like the relationship above with iron, the way that your orchid will absorb calcium will be a long effect of one chemical interacting with another, to finally produce the outcome of more calcium absorbed when Epsom Salt is applied.

This is how it works.

Magnesium is going to sit out on this round too, leaving sulfur to do the job of taking lead role. In the study “Interaction effect of calcium and sulfur on the growth and nutrient composition”  published in Plant and Soil, the authors state that when sulfur was present in the soil the more the plant absorbed calcium. The effects were very clear. (Source)

I wish I could explain how that happens, but I’m just an orchid enthusiast. Not an expert. On top that, chemistry isn’t my strong point, as I have mentioned several times before. I guess it’s just up to the chemists to figure out the why; I just know it happens. The more sulfur your potting media can absorb, the more calcium will interact and be absorbed by the roots—and sulfur is gained with Epsom salt.

Again, this is influenced by the kind of potting media you use, of course. Some media will drain all the sulfur away, and weeks later when you apply calcium, usually CalMag, the orchid media won’t have any left to absorb the calcium.

Magnesium fights with calcium, yet sulfur aids its absorption.

In the end, if you have sulfur in your potting media, the orchid will absorb more calcium when applied. Don’t apply both together unless you are using a product like CalMag, that has both. Mixing nutrients in fertilizers is never a good idea. Always wait a few weeks in between applications so that the orchid media has time to rid the excess. If you need CalMag, this link will take you to amazon to see the price. (It is an affiliate link.)

It’s hard to wrap our heads around some information sometimes because we like to be simplistic. Or that’s what I do, at least. I had believed for a long time that magnesium fights for calcium and when there is one, there is a lack of the other. But just like, there is never just one method of doing things, and there never is one reason something happens—more likely it’s five or six influences that all interfere with the outcome. The same with chemicals and how your orchid will absorb them.

Just because there is magnesium in Epsom Salt, that doesn’t mean that there isn’t sulfur and sulfur isn’t going to interact with other chemicals.

You can take the yellow away from the tip of the leaves, but this will be a slow long process. As you soak your orchid in water, or as you water it, use calcium supplements. It’s best to prevent the lack of Calcium than to try to fix it later on, so maintain a regular calcium supplement as you water.

But don’t go overboard. If you use too much calcium, and do an extreme overdose in calcium fertilization, the roots will not be able to absorb any other minerals or nutrients. Phosphorus, potassium, magnesium, boron, copper, iron, and zinc will quickly become depleted from the orchid, even if they are very present in the potting medium or in the water. The roots simply won’t be able to absorb them.

Does Adding Extra Minerals and Nutrients Eliminate Fertilizer?

You should not eliminate fertilization if you happen to start using another method to increase the levels of Magnesium, Iron and Calcium in your orchid. Fertilizers are made for specific purposes and just watering alone will not provide the right balance that you need.

How Much Calcium and Magnesium Does Tap Water Have?

If your orchid looks weak, pale, and just not growing well, you shouldn’t just start adding chemicals. First try to figure out what is lacking. You need to check with your city to verify how much calcium and magnesium that are already in your tap water. Too much can be just as beneficial as not enough, and in some scenarios, even worse.

This guide provided the basic minerals that could be lacking with the normal fertilization and a basic look at Epsom Salt. If you have any questions, you can download a 14-page fertilization guide here for free. or check out this article about 5 unique Fertilizer methods.

If you use too much Epsom Salt, you can have the opposite effect too—especially with the presence of magnesium. Magnesium is a natural fighter. It likes it’s spot as “king of the hill”. If there is too much magnesium, it will block other chemicals, inhibiting them from reaching the orchid.

 If used in excess over a  long term, Epsom salt could cause a magnesium toxicity, along with a deficiency of calcium, iron, and aluminum. This is the main focus of most articles that are published, and if the researcher’s spotlight is on them too long, you might think that magnesium is a natural inhibitor of these chemicals.

It’s not that magnesium inhibits other chemicals and nutrients, but if it is used in excess, then it does become a block. If uses sparingly, they are not in competition, especially since you won’t be watering your orchid with Epsom Salt and calcium in the same watering. You should spread them out so that periodically the orchid will get the balanced nutrients that they need throughout the year.

How Much Epsom Salt do I use for My Orchid?

To use Epsom Salt, you need to mix one tablespoon in a gallon of water and let it dissolve (The Epsom Salt company suggests two tablespoons, but every forum I’ve ever asked, the answers said they use only one.)

Mix it well.

Soak your orchid roots in the mixture for anywhere from 10 minutes to three hours. I was skeptical at the three hours tutorial I read, but these orchids were extremely dehydrated. This is a test you need to do and see what time is most beneficial for your orchid.

Use this solution four times a year or for every third or fourth watering. This solution will flush out your orchid, ridding it of excess fertilizer.

I usually don’t like to place a strict 1 tablespoon per gallon. I’ve used this before and my Phalaenopsis orchids started to turn yellow. It may be correlated or not, but some orchids are just more sensitive than others. For starters, I suggest using half a tablespoon, and see how that goes. If your orchid doesn’t complain, increase the dose to up to 2 tablespoons.

I’ve heard of misting the leaves, but this doesn’t work for me. I forget to do it. My home office is extremely dry, and I have two humidifiers running. If it were up to me to mist, my orchids would all be dead. So, misting with Epsom salt is not an option for my orchids.

When I incorporated all my fertilizers into my watering schedule, which I made into a downloadable excel spreadsheet (you can download it here for free) I had a better time at keeping up with the fertilizers I used, including the supplements like Epsom Salt.  

In all, I hope this article helped you understand what Epsom salt is and how to use it.

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