Does Epsom Salt Really Work?

Every year, as gardening season approaches, I start to see all sorts of posts and pins about Epsom salt, and how wonderful it is when used in the garden.  It is supposed to make larger, lusher plants that produce beautiful flowers and delicious fruit. 

Well, I was curious.  Does it work? Why does it work?  Are there any negative side effects?  Here’s what I discovered!

What It Is

According to Wikipedia, Epsom salt, or magnesium sulfate, is “an inorganic salt containing magnesium, sulfur, and oxygen.” Epsom salt occurs naturally, and in fact it got its name because it is produced by a bitter saline spring near Epsom, in Surrey, England.

How It’s Used

Well, according to the Epsom Salt Council (yes, this is a real thing), it has lots of uses.  But, for our purposes, it is used in the garden to help seeds germinate, and plants grow and produce lusher leaves, more flowers, and sweeter fruit.

The Science

Epsom salt contains magnesium and sulfur, which are 2 essential nutrients plants need to thrive.  Sulfur is rarely deficient in soil, but magnesium can be absent. Magnesium helps seeds germinate, aids in photosynthesis, and plays a role in the formation of fruits and seeds.  So, the idea is that you can add Epsom salt to the soil or the leaves to help increase the presence of magnesium, which will in turn help your plants thrive.

Does It Work?

Welllll, it depends. If you add Epsom salt to soil, yes, it will increase the level of magnesium and sulfur, but this isn’t always beneficial to your plants.

It all comes down to soil pH,  and if the soil is deficient in the first place. Magnesium is less available to plants in very acidic or very alkaline soil, which means that the plant cannot absorb it, no matter how much is present.  If the soil is too acidic, adding Epsom salt probably won’t help, because your plant still won’t be able to use it.  A better tactic?  Focus on getting your soil to a more neutral pH.

However, if your soil pH is neutral, and it is ALSO lacking magnesium (this can happen in sandy soil), then adding Epsom salt will help your plants.

Now, there is a difference if Epsom salt is used as a foliar spray. This means it is diluted in water and sprayed directly on the leaves.  The National Gardening Society did a small scale study of this method, and found that it did make a difference.  I think this is because if you apply the Epsom salt directly to the leaves, you bypass any soil issues that would keep the plant from absorbing magnesium.

 As for epsom salt helping seeds germinate  . .probably not so much.  Seeds have all they need already to germinate (they can even germinate in the absence of soil), and the presence  of Epsom salt shouldn’t have an impact.

How Should It Be Used?

Well, first of all, you should perform a soil test before using Epsom salt. The soil test will tell you your soil pH (how acidic or alkaline), and it will probably also tell you if there are adequate magnesium levels.  If your soil is acidic, forgo the Epsom salt.  Focus on getting your soil to a neutral pH.  If an adequate amount of magnesium is already present, you can also forgo the Epsom salt. You can purchase soil tests online, in garden centers, and from your friendly local Extension office.

Second, use it on the appropriate plants.  Lettuce and spinach don’t mind a lack of magnesium, while tomatoes, peppers, and roses generally need it. Do some research and make sure your plant needs magnesium before applying Epsom salt.

Third, opt for a foliar application.  There are lots of formulas out there, but in their tests, the National Gardening Society had gardeners use 1 tablespoon Epsom salt diluted in 1 gallon of water.  The spray was applied to peppers when the first flowers appeared, and again 10 days later.  Foliar spray was used on roses once foliage appeared, and then again every 6 weeks.  Keep in mind that too much Epsom salt can cause leaf scorch, so more isn’t always better.

Are There Any Negative Side Effects?

Yes.  If Epsom salt is sprayed on leaves, it can cause leaf scorch.  Also, there are some concerns that overuse may cause a buildup in the soil or run off into the water supply.

More Information

If you want to read more about Epsom salt and its uses in the garden, I recommend the following: Gardening:  Epsom Salt

WSU Puyallup Research & Extension Center: Epsom Salt Myths

National Gardening Association: Fertilize with Epsom Salts

Do you use Epsom salt in the garden?  What were the results?  Do you recommend it or not?  Let me know in the comments!

Linda KelsoComment