Epsom Salts as Fertilizer and Pest Control

Discovered in the well water of Epsom, England, from which the name “Epsom” salts is derived it has been used for centuries to treat a wide range of ailments, of people, animals and plants.

Epsom salt is comprised of magnesium, sulfur, and oxygen and in gardening, it is used to correct a magnesium or sulfur deficiency in the soil.

Magnesium is necessary for seed germination, as well as the production of chlorophyll. It helps to strengthen the plant’s cell walls and improves plants’ absorption of nitrogen, phosphorus, and sulfur.

A picture of a box of epsom salt next to a plant in the ground. There's two piles of epson salt next to the plant.

Can Epsom Salt Be Used As Fertilizer?

Epsom salt will allow more minerals to be absorbed via the root system, adding to healthier and stronger trees for many years. It has been shown to improve both flowering and fruit production.

In the non-edible Garden, it is suggested for use with roses.

Sulfur is also an essential element in plant development, it is needed to produce amino acids, protein, and plant enzymes.

Sulfur gives more pungent vegetables such as onions, garlic, and even broccoli their distinct flavors. Sulfur deficiency is rarely a problem in garden soils as most commonly used fertilizers, as well as manure, contain ample sulfur, as does ammonium sulfateAmmonium Sulfate.

Some vegetables have high sulfur requirements that are not routinely met by garden soils or standard fertilizers. 

Asparagus, Cabbage, cauliflower, kale, onions, radishes, Turnips and many flowering plants need a lot of sulfur to thrive.

Magnesium deficiencies are sometimes an issue. Some vegetables such as peas and beans, lettuce, spinach, and many leafy crops will produce healthy yields in soils deficient in magnesium. Other vegetables such as tomatoes, peppers, eggplant as well as fruit and nut trees need higher levels of magnesium for optimal growth.

Magnesium is the central element of the chlorophyll molecule and is essential for photosynthesis, as well as Sugar synthesis and the plants Nutrient uptake.

Plants such as blueberry, beets, broccoli, cabbage, cauliflower, celery, Corn, cucumber, eggplant, lettuce, onion, pepper, potatoes, pumpkin and squash, spinach, tomato, and watermelon respond very well to increased Magnesium.

Magnesium deficiency is not always evident until it becomes severe, in many cases at this point – it’s too late. Common symptoms include stunted growth a yellowing of the foliage, leaf curl, and poor taste quality in the fruits – [sugars are not properly concentrated]- hence you get a lack of sweetness, a bitterness, and overall undesirable flavor in many crops.

Symptoms of Magnesium Deficiency on Tomato Plants

Soils with low pH are more apt to be deficient in Magnesium, however a pH above 7, which is relatively high, can also have magnesium issues if they are high in calcium and potassium which competes with magnesium for uptake by plant roots.   See – Nutrient Disorders in Vegetable Gardens

Epsom salts are highly water-soluble, when diluted with water, and applied as a foliar spray it can be absorbed rapidly by plants. Epsom salts’ magnesium content, high water solubility, and easy application as a foliar spray are the primary reasons for the great results many gardeners report.

Warning: Excessive foliar Epsom salt applications will cause leaf burn, especially when applied on a hot, summer day. Excessive Epsom salt use can also contribute to an increase in certain diseases.

Tomatoes, peppers, and eggplants frequently suffer magnesium deficiency relatively late in the season, and display the telltale symptoms and lowered fruit yield when it is too late to correct.

They will benefit from Epsom Salt applications at both ends of the plant life cycle as well as throughout the growing season. A study by the National Gardening Association revealed that tomato and pepper plants treated with foliar applications of Epsom salts produced more bountiful and tastier fruit.

When planting or transplanting adding a tablespoon per hole is advisable. As the plant matures, a light bi-weekly foliar spray will work – 1 tablespoon of Epsom Salt per gallon of water. You can also work in a tablespoon of Epsom Salt per foot of plant height around the base of tomato plants, slightly less in eggplant and Peppers.

Flowers, shrubs, and even lawns will benefit from Epsom salt. A modest amount when planting and periodic foliar spraying add to the optimal aesthetic value of your landscape.

Epsom Salt for Pest Control

The jury is out on whether or not Epsom Salt actually helps control insects. Many Old Timers swear by it. Magnesium SulfateMagnesium Sulfate is most definitely toxic to pests, they die after consuming it, as to which pests will consume it is uncertain as many are deterred by it.

Epsom salts are believed to repel beetles, when sprinkled dry it will deter slugs and snails. Epsom salt sprinkled on your garden border will help to keep varmints such as squirrels, woodchucks, and rabbits away.

Cleaning garden tools with Epsom salt will remove any oils from plants, poison ivy, poison oak, and some fungal residues.

To get rid of unwanted tree stumps, drill holes in the stump and fill it Epsom salt, nature will work the salts into the stump and expedite its biodegradation.

Which plants like Epsom salt?

Epsom salts is a form of magnesium, which is an element that is essential for plant photosynthesis. This means that virtually all plants can benefit from the addition of Epsom salts if they are being grown in soil that is magnesium deficient. The most reliable way to determine if your soil is lacking magnesium is to perform a soil test.

Some plants are more likely to benefit from high levels of magnesium, including tomatoes, peppers, and rose bushes. Epsom salts will improve how quickly these plants grow and deliver a more bountiful crop of food or flowers. Plants like beans and leafy vegetables are less dependent on magnesium and will grow well even if magnesium levels are low.

Can too much Epsom salt hurt plants?

Although plants need magnesium to grow, it’s important to remember that it is a minor nutrient. They don’t need much of it and most soils already have enough magnesium present to support plant growth.

If you add too much Epsom salt, it may inhibit the ability of your plants to take in calcium, causing a severe nutrient deficiency. This type of soil toxicity can lead to problems like blossom end rot.

Can i use Epsom salt on potted plants?

Yes, you can. However, care should be taken as potted plants are more likely to suffer from nutrient buildup and soil toxicity as the soil is enclosed in a pot. In most cases, a balanced fertilizer that contains macro and micro nutrients is all that is required for potted plants.

How much Epsom salt to put on tomato plants?

Tomatoes often benefit from the addition of Epsom salt. Epsom salt can be used in multiple ways:

Place in seedling holes
When you first plant your tomato seedlings, place a tablespoon of Epsom salts mixed with soil at the bottom of the seedling hole. Cover with a little more soil, then place the seedling and water in.

Side dressing during the growing season
After 3-4 weeks, you can begin using Epsom salts as a side dressing. Place one tablespoon of Epsom salt per foot of plant height around the base of the plant. Apply every 5-6 weeks.

Spraying on foliage
The best time to start spraying tomato plant foliage is when the first blooms have appeared. Simply add two tablespoons of Epsom salt to a gallon of water and place in a sprayer. Spray this solution on your plants once a month.

How often should i use Epsom salts for my plants?

Epsom salts don’t need to be applied very often. For magnesium hungry plants like tomatoes, peppers, and roses, apply Epsom salts as a side dressing every 5 to 6 weeks. Use about one tablespoon of Epsom salt per foot of plant height. You can also apply diluted Epsom salts to foliage once a month. 

Double this timespan for plants that are less reliant on magnesium. Ideally, test your soil for magnesium content before using Epsom salt, as you may not need to use it.

Can Epsom salt kill bugs?

Yes, Epsom salt has been shown to deter slugs, snails, beetles and other bugs when placed on the ground as a side dressing or sprayed onto leaves. However, it is not as effective as other types of pest deterrents. 

What toxins does Epsom salts remove?

Epsom salts doesn’t remove toxins from plants or soil. However, it can be used in place of toxic pest killers or synthetic fertilizers. This can help you reduce or eliminate potential toxins in your garden. Epsom salts doesn’t remove toxins from plants or soil. However, it can be used in place of toxic pest killers or synthetic fertilizers. This can help you reduce or eliminate potential toxins in your garden. 

Does Epsom salt kill aphids?

Yes, it can. Create an Epsom salt spray, combining 1 gallon of water, 2 tablespoons of Epsom salt, and 1-2 teaspoons of natural soap. Shake the solution well then spray directly onto the aphids. It’s a great way to get rid of aphids on roses, as you are also giving the roses a dose of magnesium.

Can Epsom salts be used as ant control?

Yes, Epsom salts can be used to deter or kill ants in a couple of ways. The first technique is to place piles of Epsom salt in your garden or around your home to keep them away. The second option is to dissolve a cup of Epsom salt in five gallons of water and spray in locations where ants are present.

What plants don’t like Epsom salt?

There aren’t any plants that don’t like Epsom salt. However, it is worth remembering that some plants don’t need much magnesium. For these plants, Epsom salts is only beneficial if there is a magnesium deficiency in the soil and most soils and NOT magnesium deficient. 

Does Epsom salt kill earthworms?

Yes, in very high doses, Epsom salt can kill earthworms. This is one of the reasons why gardeners should be cautious when using Epsom salt in the garden. The best approach is to use a soil test to determine if your soil is magnesium deficient and only applying Epsom salts if it is.

Does Epsom sats kill termites?

Yes, very salty can be used to kill termites. Make a solution that is 50% water and 50% Epsom salt. Inject the solution into woodwork where termites are present. 

Related: Using Epsom Salt in Hydroponic Gardens