How to Use Epsom Salt for Healthier Plants and Soil

Are you searching for a solution to save that sad-looking indoor plant, or need some help getting your garden to flourish? The answer may be simpler than you think, and you may already have this product sitting in your cabinet. Many gardeners turn to Epsom salt in an effort to get their potted plants and gardens to thrive. But should you use Epsom salt on your plants?

We went straight to the experts to learn more about this gardening hack and how to use it correctly to grow your plants to their full potential. 

What Does Epsom Salt Do for Plants? 

"Epsom salt, also known as magnesium sulfate, is a popular garden remedy that replenishes essential nutrients like magnesium and sulfur in soil," Omelchenko says. "Magnesium plays a critical role in photosynthesis as part of the chlorophyll molecule, while sulfur is vital for the synthesis of amino acids, vitamins, proteins, and carbohydrates. Whether you need to apply Epsom salt depends on the state of the soil and plants."

Why You Should Use Epsom Salt in Your Garden

Heinrich, a horticulturist and botanical designer, says plants need six major nutrients and 11 minor nutrients to be healthy and to thrive. "Suppose you have healthy, fertile soil that's regularly amended with organic compost and manure," he says. "In that case, you probably don't need to add any manufactured fertilizer to the soil because it already has everything your plants need to grow strong and healthy."

However, if you have poor soil that isn't rich in nutrients, Heinrich explains, you may need to fertilize it with the top three macronutrients, nitrogen, phosphorus, and potassium—also known as NPK—as well as the three lesser macronutrients, magnesium, sulfur, and potassium. "As you can see, Epsom salt—magnesium sulfate—includes two of those lesser macronutrients," he says.

"Epsom salt will help your plants absorb all the other nutrients from the soil," he says. "Your plants will have healthier-looking foliage, and it can even improve the flavor of your fruits and vegetables, making them sweeter and more nutrient-rich."

Benefits of Using Epsom Salt on Plants

Omelchenko says that using Epsom salt can benefit plants in several ways. For example, if a plant is deficient in magnesium, its leaves can become pale and yellow—a condition known as chlorosis. Epsom salt can prevent this by providing the necessary magnesium. Since Epsom salt promotes chlorophyll production, it can also help make the foliage green and lush. Some gardeners also report that Epsom salt helps increase flower and fruit production.

She also states that a lack of sulfur inhibits the synthesis of proteins, carbohydrates, and other substances needed by the plant. "Sulfur is part of enzymes and other compounds necessary for nitrogen assimilation, and its absence can impede nitrogen metabolism," she says. "This, in turn, can lead to chlorosis due to nitrogen deficiency and reduce the rate of growth."

She continues, explaining, "Epsom salt can increase sulfur levels, which will help the plant grow and develop more vigorously. Additionally, sulfur affects the quality of the crop by improving the protein and oil content of the fruit."

Heinrich says that if you have a new garden plot with soil that is not yet amended and rich in natural nutrients and minerals, Epsom salt is a great way to fortify your plants with some of the vital nutrients they need to thrive.

Epsom salt is also beneficial for potted vegetables. "Tomatoes and other vegetables can quickly absorb the nutrients out of the soil when they are in containers; that's why supplementing with Epsom salt and other water-soluble fertilizers is important to keep your potted plants healthy and vital," he informs. 

Disadvantages of Using Epsom Salt on Plants

"Epsom salt may seem like a miracle cure, but it can have its drawbacks and should be used with caution," Omelchenko advises. She continues, "If your soil is already rich in magnesium, adding Epsom salt can cause an imbalance by interfering with the absorption of other minerals, such as calcium and potassium. Excessive use of Epsom salt can lead to salinization, which can negatively impact plant health by making it difficult for plants to absorb water and nutrients."

She adds, "This can lead to drought stress symptoms, nutrient deficiencies, and in severe cases, the death of the plant. Excessive use of magnesium sulfate can also contaminate local water sources."

Heinrich warns that overuse of Epsom salt in your garden will stunt the growth of your vegetables or even burn them. "You should use [Epsom salt] sparingly and only twice during the growing period. Once you build up your soils with organic compost and manure, you may only need to feed with Epsom salt once during the midpoint of the season," he explains.  

How to Determine If Your Plants Need Epsom Salt

Although Epsom salt has benefits, you need to be sure that your plants actually need them before you start supplementing your flora. Omelchenko says that the best way to do this is to have your soil analyzed. Soil tests can provide information about pH levels and nutrient content.

She also advises inspecting your plants for signs of magnesium deficiency. "Look for symptoms such as interveinal chlorosis, which is characterized by spots and streaks of light green and then yellow between the green leaf veins," she says. "The edges of leaves may turn yellow, orange, red, or dark red."

She continues, "Signs of magnesium deficiency first appear on older leaves and then spread to younger leaves and other parts of the plant."

How Do You Use Epsom Salt on Plants? 

So, how do you apply Epsom salt if your plants need it? There are actually a couple of ways you can use it on your plants. But before you reach for that bag of Epsom salt, you need to ensure it isn’t formulated with any additional ingredients that aren’t good for plants. It’s best to use unscented, plain Epsom salt for internal and external use on plants.

That being said, here are a few simple application methods the experts recommend:

Spray the Leaves

Omelchenko says that Epsom salt can be used as a foliar fertilizer, which involves spraying the solution on the leaves. This method is particularly effective for quickly treating magnesium deficiency.

"To prepare an Epsom salt solution, mix 1–2 tablespoons of Epsom salt with one gallon of water. You can use this solution to spray the leaves or water the soil," she says. "It's important to remember that different plant species have varying leaf thickness. Some have thicker protective layers, while others are more delicate and sensitive to treatment."

She continues, “For foliar applications, it's a good idea to test the solution on a few leaves of each plant before spraying the entire plant. This allows you to observe and ensure that the solution doesn’t cause chemical burns, which appear as yellow or light brown dry spots. If you notice spots, add more water to the solution to dilute it. Perform the treatment once a month.”

Water it Into the Soil

Another method for applying Epsom salt to plants is to mix it with water and water it into the soil. Omelchenko says you should avoid adding dry Epsom salt directly to the soil, as it can lead to soil salinization and chemical burns. Dissolving it in water ensures that the roots can properly absorb magnesium and sulfur, promoting healthy growth without harming the plants.

“It's important not to do this too often or in high concentrations to avoid chemical burns and other negative effects," Omelchenko says. "As with other fertilizers, I recommend watering the plant abundantly a few hours before application to avoid burning the roots, which are more vulnerable when the soil is dry."

Heinrich says that the most common mistake people make when using Epsom salt in their garden is using too much.  "You only need to put a tablespoon of Epsom salt in a gallon of water and water it into the root zone of your cucumbers, tomatoes, eggplants, melons, and other vegetables," he informs. "This feeding should only be done twice a year: once when the plants are first planted and again halfway through the growing season."

He continues, "If you feed every other week or several times per month, as some gardening influencers have suggested, your plants cannot effectively transport nutrients from the roots to the leaves and fruits."

So, similar to seasoning your food, you don't want to get your plants too salty. But by applying these expert tips you can provide your plants with the right amount of Epsom salt to get them looking lush in no time.