Epsom Salt For Tomatoes: Why is Epsom Good For Tomato Plants?

Tomatoes are one of the most popular and beloved garden plants grown the world over.

While many people are aware of their needs for nitrogen, phosphorus, and soluble potash fertilizing needs tomatoes also need other trace minerals and soil components like magnesium to truly thrive.

As strange as it might sound, the same Epsom salt that you might already be using to soak your sore feet can also be used to help boost the tomato plants in your garden.

If you look closely at the ingredients label you will find that primary ingredient is magnesium sulfate. Most of these packages even include directions for watering or fertilizing tomato plants with Epsom salt.

This begs the question, is Epsom Good For Tomato Plants?

The short answer is that yes, in certain conditions a little bit of Epsom salt can help your tomato plants.

However, the size, development stage, and state of your soil can impact just how much and how often you should use Epsom salt on tomato plants, as well as the best method for applying it.

In this article, we’ll take a closer look at Why Use Epsom Salt On Tomato Plants, how it can help your tomatoes, and how to use Epsom salt for tomatoes for the given conditions.

What Is Epsom Salt?

By definition a “Salt” is technically classified as a compound of two elements, one with a positive ion and one with a negative ion.

While Sodium-Chloride (Table Salt) is a salt, and known to damage plants, it is not the only salt on Earth. Indeed, there are some salts, like Epsom salt that can be beneficial to plants.

Epsom salt is made up of Magnesium and Sulfur which plants already use in various ways. As a product it was first introduced as a kind of self-care product that was boasted to help with sore muscles, fight cold symptoms, and could even be blended into medicated salves to treat minor flesh wounds.

What Does Epsom Salt Do For Tomato Plants?

Epsom salt has since evolved for other uses including the garden. This is largely related to the fact that both magnesium and sulfurare important for the processes of growth in many plants, especially tomato plants.

In fact, these mineral-based micronutrients play an essential role in things like photosynthesis, protein synthesis, and the process of producing a healthy cell wall structure. 

This is likely the impetus for old fashioned homespun gardening remedies like burying eggshells and banana peels in the garden near the tomatoes.

Except with Epsom salt, you don’t have raccoons encouraged to root around in your garden soil!

Is Epsom Salt Good For Tomato Plants?

If you have healthy soil chances are you don’t need to add Epsom salt into the equation. Most of the time the tomato plant will tell you if it needs Epsom salt. In fact, the most common cause of low soil magnesium levels comes from overwatering plants.

Many a novice gardener has started their tomatoes from seed only to panic when the first true leaves develop a shade of yellow with green veins.

In just about any plant this is a sign that the leaf itself has started consuming more sugar compounds than it is producing through photosynthesis. You see when you overwater the plant, it dilutes the soil minerals.

This includes magnesium which plays a critical role in the sugar production process of photosynthesis.

When Should I Use Epsom Salt On My Tomatoes?

There are a few different conditions where you may need to fertilize your tomatoes with Epsom salt.

The first is an overwatered seedling, or a seedling that is in poor quality potting soil. This usually manifests as leaves that are turning yellow, just other vegetables, yet have green veins.

When planting a tomato seedling, you should bury it up to the bottom of the lowest true leaves. Before backfilling the hole you can apply some Epsom salt to the surrounding soil. 

This will help provide it with an added mineral boost of magnesium. At the same time the sulfur component will also help mitigate any alkaline characteristics that might exist in the soil.

Another time when Epsom salt might be needed is when a more mature tomato plant has been overwatered by you or by seasonal rainfall. This again tends to manifest as yellow leaves with green veins. It might also cause the plant’s branches to look limp, or otherwise grow slowly.

This is true for tomatoes in containers, as well as in the garden. In fact container grown tomatoes are even more prone to over-watering due to their limited volume of soil.

How Often Do You Put Epsom Salt On Tomatoes?

This can vary depending on the type of situation you are trying to address. Once any over-watering symptoms have been dealt with, you can apply Epsom salt to a mature tomato plant every 3 to 4 weeks. Just bear in mind that the amount the plant needs will vary depending on it’s size.

How To Use Epsom Salt For Tomatoes

There are a few different ways to use Epsom salt on tomatoes plants depending on the state of the soil and the stage of the plant.

The overarching goal is to get the Epsom salt’s magnesium to the roots as soon as possible, without stressing out the plant. 

1. Epsom Salt For An Overwatered Tomato Seedling

If you are dealing with an overwatered tomato seedling, you don’t want to give it even more water. Yet you still want to get the mineral benefits of the Epsom salt to the roots.

In this situation, the best option is to move the seedling to a location that will accelerate the drying process. A sunny window that also helps maximize the photosynthesis the plant is still capable of performing is ideal.

You might want to also cut away the bottom of the pot or clear the drain holes to make sure any lingering water can escape. When the seedling has sufficiently dried out, you can then water it with dissolved Epsom salt.

How Do I Prepare An Epsom Salt Solution?

The soil doesn’t necessarily need to be bone dry before you give the plant an Epsom salt solution. You just don’t want it to be saturated. Lightly dry will suffice.

When it comes to preparing the solution, the package usually includes its own recommended method. Just remember that the overarching goal is to fully dissolve the Epsom salt into the water or at least dissolve as much of it as you can.

The ideal Epsom salt solution ratio for tomatoes is 1 tablespoon of Epsom salt dissolved into one gallon of water. If your soil is overly sandy or simply nutrient-poor, you could double this concentration without any complications.

If you have a mortar and pestle, you should consider grinding a small amount of Epsom salt into a fine powder similar to the texture of table salt.

This will maximize the available surface area to interact and essentially dissolve into solution with the water.

• Step One: Add 1 tablespoon of Epsom salt to clear plastic, one-gallon container.
• Step Two: Add one gallon of hot water to the container.
• Step Three: Seal the container and shake vigorously for a full minute. Then set the container down and let it settle for a minute or two.
• Step Four: Lift the container and look at the bottom for undissolved grains of Epsom salt. If necessary, shake the container again to agitate the Epsom salt into solution with the water.
• Step Five: Let the container sit on the counter for 10 to 15-minutes to let it cool before administering it to the plants.

In this type of application, you want to directly apply the Epsom salt solution to the soil surrounding the roots. A small watering can is preferable to a garden sprayer or a mister.

2. Epsom Salt For An Overwatered Mature Tomato Plant

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If you are dealing with a mature plant that’s been overwatered in your garden or in a container, you don’t want to further inundate it.

Yet it’s also much harder to dry out a larger volume of soil. In a case like this, it’s often better to side dress the plant.

3. Side Dressing A Maturing Tomato Plant With Epsom Salt

Side dressing a maturing tomato plant with Epsom salt can also be a nice way to promote growth and photosynthesis during the peak of the growing season. The correct dosage will need to be based on the overall size and height of the plant.

How Much Epsom Salt For Tomatoes?

The general rule of thumb is to apply one teaspoon of epsom salt per foot of the height of the tomato plant. This measurement should be taken from the soil level to the top of the foliage.

You shouldn’t attempt to pull or lift a branch. For example, a plant that measures three feet tall would need three teaspoons of epsom salt for side dressing.

Just like when you are preparing an Epsom salt solution it can help to grind the granules to a table salt consistency.

If there is a rainstorm forecasted in the coming day or so, all the better. If not, be prepared to lightly water the plant that day.

• Step One: Measure the plant from two different angles for accuracy.
• Step Two: Measure out and prepare the correct amount of Epsom salt.
• Step Three: Lightly rough the surface soil with your fingers to create enough texture to hold the Epsom salt.
• Step Four: Take finger “Pinches” of Epsom salt and lightly sprinkle it on the soil directly under the foliage or drip edge of the plant.

If the soil isn’t overly wet, or there isn’t rain in the upcoming forecast, you can lightly water the plant with the garden hose.

4. Applying Epsom Salt As A Soil Drench OR A Foliar Spray

There are some gardeners who standby the foliar spray as their preferred option for applying Epsom salt to tomato plants.

The idea behind this is that the leaves might uptake some of the magnesium sulfate directly, or the Epsom salt solution will drip down to directly feed the roots.

The concern with using an Epsom salt foliar spray is that wet tomato leaves tend to be at a greater risk for a fungal diseases like early blight.

This is even more likely to be a concern if local weather conditions have been especially humid, or your soil has a history of harboring fungal diseases.

To do so, you simply prepare a solution of Epsom salt in warm water. Let it cool. Then pour it into a garden sprayer or a hand spray bottle. You can then mist the foliage.

Is There Such A Thing As Too Much Epsom Salt?

Yes, it is possible to give a tomato plant too much Epsom salt. However, Epsom salt is relatively forgiving. Especially if local conditions have been overly wet or you have sandy soil.

The prevailing wisdom is that a mature plant in the peak of the growing season should not be given more than one tablespoon of Epsom salt in a single month.

Does Epsom Salt Help Prevent Blossom End Rot?

Unfortunately, Epsom salt does not prevent blossom end rot, the dreaded blossom end rot has nothing to do with the magnesium or sulfur components of Epsom salt.

While blossom end rot is related to mineral deficiency in the plant and the soil, the key mineral involved is calcium. In certain conditions, the magnesium of Epsom salt can compete with available soil calcium especially if your soil already has an overly acidic pH.

If you have noticed early signs of blossom end rot, in a mature plant that is starting to set fruit, it’s best to treat it before adding magnesium.

This calls for dissolving dolomitic “Garden Lime” in water or side dressing it. Then give the plant a solid week or two to absorb the calcium through the roots before applying Epsom salt. 

Just bear in mind that any existing fruit that has been compromised by blossom end rot will not “Heal.” They are essentially lost, and it’s best to carefully pick and discard them.

Will A Plant Treated With Epsom Salt Produce A Sweeter Tasting Tomato?

There’s a fair amount of debate wrapped around this question. It can be hard to separate the science from folklore.

On a chemical level,the micronutrients magnesium and sulfur in Epsom salt play an important role in how the plant absorbs soil nutrients as well as boosting photosynthesis.

The more photosynthesis the plant engages in the more sugar it produces. The plant then allocates those sugar compounds to the fruit for storage.

Yet there aren’t any hard and fast scientific facts that clearly prove Epsom salt-treated plants produce sweeter tomatoes. It’s important to note that the state of the fruit when it is picked likely has a larger impact on “Sweetness.”

If you’ve ever taken a bite of a green tomato off the vine you likely found it to be bitter. This is because the sugar and many of the other flavor compounds are locked up in relatively flavorless starch. It’s only the ripening process that unlocks sugar compounds that your tongue can taste.

Ultimately, fully ripe tomato from a plant that wasn’t treated by Epsom salt will be sweeter than a tomato that was picked when it was partially ripe, from an Epsom salt-treated plant.

Adding to this folklore is the impact of soil minerals on flavor. There are some tomato varieties that supposedly draw up more minerals than others.

The popular “Black Krim” from the Crimean region of Asia supposedly pulls up more soil minerals, which contributes to its the visually interesting purple bottom and “Green Shoulders.”

Just how much these micronutrients in the soil contribute to the flavor of the tomato is again up for debate. It’s not currently known if high mineral salt levels can indeed boost the depth of flavor in the fruit.

Too little micronutrient minerals can stress a plant and prevent it from producing fruit, much like a plant that has received too many supplemental minerals.

Is Epsom Salt An Effective Fertilizer?

On its own Epsom salt is not an effective fertilizer for tomatoes. It won’t promote root development or foliage growth. To do that you need a fertilizer with nitrogen to promote foliage, and phosphorus to promote root development.

However, Epsom salt can still help a tomato plant where the soil is too alkaline or one that has been overwatered. In this way, it helps boost absorption as well as improving photosynthesis in the existing foliage.

Can An Epsom Salt Foliar Spray Help With Pest Control?

There are many different types of insects that love to feast on tomato plants. This includes things like hornworms, moth larvae, aphids, beetles, and even the odd tomato-stealing chipmunk.

Unfortunately, Epsom salt itself does not help with pest control on tomato plants. In most of these cases, you will need to handpick pests, trap them or spray an organic deterrent like neem oil.

Planting things like French Marigolds might help deter moths. Planting dill near tomatoes can also attract hornworms, which are easily handpicked before they make their way to the more vulnerable tomato plants.

In Conclusion

Epsom salt offers some benefits for tomatoes as well as many other popular garden plants like peppers, and tomatillos. Yet, it isn’t necessarily a make-or-break soil supplement.

If you have overly sandy soil, tilling some Epsom salt in the spring will likely help maintain mineral levels. It might even be part of a strategy for adjusting the pH of slightly alkaline soil. Otherwise, it’s probably best to let the plants or seedlings tell you if they need Epsom salt.

If you see the telltale sign of yellow leaves with green veins, you should consider applying some Epsom salt solution or side dressing the plant. It might also be a good idea to make some changes to your watering strategy.

Most of the time, mineral deficiencies like this are related to overwatering. Side dressing with some Epsom salt and dialing back the water the plant receives might be all that’s needed to restore the natural balance.