By: Raffaele Di Lallo, Author and founder of Ohio Tropics houseplant care blog
Have you ever wondered about using Epsom salts for houseplants? There is debate as to the validity of whether Epsom salts work for houseplants, but you can try it out and determine for yourself.
Epsom salt is composed of magnesium sulfate (MgSO4) and many of us may be familiar with it already from soaking in an Epsom salt bath to alleviate sore muscles. It turns out that this can also be good for your houseplants!
Epsom salts would be used if your plants exhibit a magnesium deficiency. Although both magnesium and sulfur are very important, it is usually not a problem in most soil blends unless your potting mix is highly leached out over time through continued watering.
The only real way to tell if you have a deficiency is to complete soil testing. This isn’t really practical for indoor gardening and is most often used to test soil in outdoor gardens.
So how is Epsom salt good for houseplants? When does it make sense to use them? The answer is only if your plants exhibit signs of magnesium deficiency.
How do you know if your houseplants have a magnesium deficiency? One possible indicator is if your leaves are turning yellow in between green veins. If you see this, you can try an indoor Epsom salt remedy.
Mix about one tablespoon of Epsom salt to a gallon of water and use this solution once a month to water your plant until the solution comes through the drainage hole. You can also use this solution as a foliar spray on your houseplants. Place the solution in a spray bottle and use it to mist all exposed parts of the houseplant. This type of application will work quicker than application through the roots.
Remember, there really is no reason to use Epsom salts unless your plant exhibits signs of magnesium deficiency. If you apply when there is no sign of deficiency, you may actually be harming your houseplants by increase the salt buildup in your soil.
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Read more about Soil, Fixes & Fertilizers
Epsom salts help nourish your houseplants by providing magnesium--the building block of leaves' green chlorophyll pigment. Also known as magnesium sulfate, Epsom salts dissolve readily in water and absorb into roots when soaked into the soil. Being organic, these nonsalt crystals do not harm plants, even when you accidentally add a bit too much when making a dosage.
Fill your watering can or container with 1 gallon of water. Allow the filled container to rest for at least an hour to warm to room temperature and allow any chlorine additives to evaporate.
Measure 1 tsp. of Epsom salts, add it to the water, and stir it in.
Water your houseplants with the solution, following the same procedure you've always done when watering.
Repeat the application of the Epsom salts solution to your houseplants again in three or four weeks. Use regular water for any watering needed between times.
You may simply add a pinch or two of Epsom salts anytime you water rather than scheduling a specific Epsom salt watering. Don't go overboard. Plants usually don't grow in soils that lack magnesium, so just a light application of Epsom salts now and then works perfectly. Also don't fret if you accidentally add a tablespoon per gallon it won't harm the plant.
Avoid using cold water or water still smelling of municipal chlorine treatments. Chlorine in excess causes yellowing of houseplant foliage edges and leads to plant decline over long periods.
Epsom salt is a natural mineral that is made from hydrated magnesium sulfate. It was discovered in an underground spring in the town of Epsom in England in the early 1600s. It has since been used for treating many conditions in humans, animals, and plants. Chemically, it has 10% magnesium and 13% sulfur. These are nutrients that are essential to many plants for the roles they play in growth and development.
Epsom salts attach to excess fertilizer salts in houseplant potting soil and help remove them. Signs of fertilizer salt buildup in houseplant potting soil include dried or burned leaf margins and wilting, both of which are due to root damage. To leach fertilizer salts from an indoor palm's potting soil, mix 1 teaspoon of Epsom salts into 1 gallon of water, put the palm container in a sink or bathtub and very slowly pour the solution into the pot. Stop when the water appears through the drainage holes and wait until it's drained away. Pour the Epsom salt solution into the pot three or four times and leave the pot to drain before returning it to its usual position.
So we have seen that epsom salt CAN be beneficial to some specific plant crops in very specific industrial conditions. This is related solely to high-production soil that is deficient in magnesium. But are there other benefits beyond soil magnesium deficiency? Pinterest certainly indicates that there must be!
“Epsom salt – actually magnesium sulfate – helps seeds germinate, makes plants grow bushier, produces more flowers, increases chlorophyll production and deters pests, such as slugs and voles. It also provides vital nutrients to supplement your regular fertilizer”
Six Ways to Use Epsom Salt in the Garden, The Epsom Salt Council
The quote above is from The Epsom Salt Council, and it sums up many gardeners’ perspective of the usefulness of magnesium sulphate in the garden. There are likely countless more perceived benefits of epsom salt in the garden circulating around out there.
Beyond adding magnesium to the soil, none of these advertised benefits are substantiated by scientific research. The article “Miracle, Myth, or Marketing: Epsom Salts,” by Dr. Linda Chalker Scott (Washington State University) is particularly insightful on why each of these perceived benefits are mythical. Trust me, it’s a worthwhile read!
If you still reeeeaaallly want to use epsom salt in your garden, I suggest referring to the article “Fertilize with Epsom Salt” on Garden.org. Written by horticulturalist Charlie Nardozzi, this article describes how home gardeners could use epsom salts, particularly as a foliar spray. But as the article states, “Before you try Epsom salts, test the soil to determine its magnesium content.” Use the kind of soil test that gets sent off to a laboratory (not the at-home kind).
Further Reading: How to Test Garden Soil
The myth is that Epsom salts, or magnesium sulfate, is a safe and natural home remedy you can use to increase plant growth. You can find information from all kinds of sources that swear by using Epsom salts for great roses, to get their turf greener, and to control pests, but there is no science behind any of this. The only time that it does any good to add Epsom salts is if you have a magnesium deficiency, and a soil test will tell you if you have one.Gardening Course: The Science of Gardening, from The Great Courses, by Dr. Linda Chalker-Scott
Any fertilizer should only be added to the garden if it is in fact required and the risk of applying it is acceptable. When considering risk, remember that the ratio of magnesium to calcium is very important for nutrient uptake in plants. This includes plants in your yard and plants in the wider ecosystem. Healthy soil generally has 10x more calcium than magnesium. The actions of humans can upset the natural balance of the soil ecosystem. It’s true that plants need magnesium, but there really can be too much of a good thing.
Also know that the epsom salt you buy in a big jug at the pharmacy is not necessarily a “natural” product. Epsom salts that you buy in a big jug probably came out of a chemical plant in Illinois rather than from some kind of artisanal local rock quarry. But we’ll get into that later on!
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.