Beware Of Using Epsom Salt For Tomatoes (Here’s Why)

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Epsom salt has long been touted as a quick fix for basically anything in the garden. I’ve seen it said that it can fix blossom end rot, stunted plant growth, yellowing leaves, and more in tomato plants.

Well, not to ruin your day, but epsom salt is more likely to harm your tomatoes than help them. In this article, I’ll share the reality of what epsom salt does for tomatoes and other veggies.

Epsom salt for tomatoes
Epsom salt near tomatoes in the garden.

What Is Epsom Salt?

Pure epsom salt is made up of magnesium sulfate. Essentially, it is a water-soluble crystallized salt that contains magnesium and sulfur.

The word Epsom comes from the English town where the compound was first discovered. Since then, it has been widely used as a bath soak to help many ailments.

Epsom salt crystals in hand near tomato plant
Crystallized epsom salt (magnesium sulfate).

It is still used today as a primary ingredient in bath soak products and is considered beneficial. Many claim that epsom salt helps reduce inflammation, soreness, and muscle aches. However, there is little scientific research backing up the claims.


What Does Epsom Salt Do For Tomatoes?

When you dissolve epsom salt in water, then water your plants, you’ll be adding magnesium and sulfur to the soil. Both of these compounds are in fact necessary for growing tomatoes.

However, many soils already have plenty of magnesium and sulfur to begin with. In this case, adding more may have negative consequences on your tomatoes.

But Tomatoes Need Magnesium, Right?

Yes, tomatoes require magnesium for proper plant development. A magnesium deficiency in the plants will cause chlorosis (yellowing leaves) between the veins of tomato leaves. This will begin at the lowest leaves of the plant and work its way up over time.

So why not add epsom salt to your soil? Well, if the soil already has enough magnesium, it is a bad idea to overload it with excess. Too much magnesium in the soil can actually lock out availability of calcium, another vital nutrient.

This imbalance between magnesium and calcium can lead to blossom end rot and other calcium deficiency symptoms. It is critical to know your soil’s nutrient content, first.

When Should I Add Epsom Salts?

If you’ve already got yourself a bag of epsom salts, don’t feel the need to throw it away. It may still be handy in the garden in select circumstances.

  • Magnesium deficiency. The only way to know for sure that you have a magnesium deficiency is to get a soil test. This will indicate the level of nutrients in your ground soil and make specific recommendations to improve it. Epsom salt may come in handy in this case.

A soil test is a great idea, especially in a new garden, or one that has seen failures. If you have especially sandy soil, it is possible that magnesium is deficient, but not guaranteed. Send away some of your soil to know for sure.

Always be careful with the amount of epsom salt you are adding to your soil, as magnesium is a secondary nutrient. This means that it is required for plant growth, but in small quantities. Ultimately, it is best to leave this to the professionals who manufacture fertilizers.

What Should I Use Instead?

It is much safer to use an all-purpose fertilizer that contains magnesium and calcium, such as Espoma Garden or Tomato Tone, or similar. Too much of one can lock out the other nutrient from your plants, leading to growth issues.

Garden Tone all purpose fertilizer bag near raised bed
Many all-purpose fertilizers contain a balance of magnesium and calcium.

Many gardeners recommend putting a tablespoon or so of epsom salt into the hole when you transplant your tomatoes. This is very unscientific, and I just wouldn’t recommend it.

Instead, simply use a nutrient-rich potting soil for container plants (this soil has worked amazingly well for me).

Fox Farm Happy Frog soil bag
Happy Frog is a great potting soil for growing tomatoes.

If you’re growing in the ground, amend your garden soil with compost or all-purpose fertilizer. These balanced additions will add all the required nutrients on a slow-release schedule that is unlikely to cause problems.

Remember, epsom salt is not a fix-it-all amendment and should not just be tossed in for the heck of it! You may just end up doing your tomato plants a disservice.


Can I Spray Epsom Salt On Tomato Leaves?

Okay, so epsom salt may not be the best idea to add to your soil, but what about as a foliar spray? Many claim that dissolving some in water and spritzing tomato leaves can alleviate a deficiency, improve yellowing leaves, and even stop blossom end rot.

However, the only thing you should expect after spraying your tomatoes with an epsom salt solution is a sunburn. Spraying tomato leaves with epsom salt can easily cause sun scald, or white burn marks on the leaves.

Sun scald on tomato leaves
Sun scald on tomato leaves.

Many gardeners are set in their ways and may dismiss this article, continuing to add magnesium sulfate to their soil. However, I recommend only adding what you know your tomatoes need to thrive. Happy growing!

1 thought on “Beware Of Using Epsom Salt For Tomatoes (Here’s Why)”

  1. I try to buy Miracle Grow for tomatoes/veggies. I have sprayed my tomato leaves only once this year with a water/epsom mix. It has been a while so I don’t think some of the yellowing leaves I see now is ‘because’ of that. . So, I am thinking maybe I should do it again on just the tomato plants that have some yellowing leaves. If I do it early in the morning time will that be any ways beneficial — avoiding the sun burning the leaves. . or would it possibly burn them anyway.
    And, kind of different subject. . I usually buy different varieties, and the Better Bush seems to keep greener leaves than some of the other ones.. Is that a good thing?

    Reply

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