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Can Epsom salt prevent fungus on plants?

Epsom salt, also known as magnesium sulfate, is a mineral compound that has many uses in the garden. One of the purported benefits of Epsom salt is its ability to prevent or treat fungal diseases in plants. But does Epsom salt really work for controlling plant fungus? Let’s take a closer look at the evidence.

What is Epsom Salt?

Epsom salt is a naturally occurring mineral compound composed of magnesium, sulfur, and oxygen. It gets its name from the town of Epsom in England, where it was originally discovered in mineral springs.

Some key facts about Epsom salt:

  • Chemical formula: MgSO4·7H2O
  • Contains magnesium and sulfur, both nutrients plants need
  • Readily dissolves in water
  • Available at most pharmacies and garden/home stores
  • Relatively inexpensive

In gardens, Epsom salt is used for a variety of purposes:

  • As a fertilizer to provide magnesium and sulfur
  • As a foliar spray to boost nutrient absorption
  • To improve seed germination
  • To deter pests
  • To increase flowers on roses and other plants
  • To prevent and treat fungal diseases

It’s this last use – fungal disease control – that we’ll explore in depth in this article.

What Causes Fungus on Plants?

There are many different types of fungal pathogens that can attack garden and houseplants. Some common plant fungal diseases include:

  • Powdery mildew
  • Downy mildew
  • Botrytis or gray mold
  • Anthracnose
  • Leaf spot
  • Rust
  • Root rot

These plant diseases are caused by fungal organisms that attack the plant tissue. They spread through reproductive spores that travel by wind, water, insects, and infected gardening tools or hands. Fungi thrive in warm, humid conditions.

Factors that can increase a plant’s susceptibility to fungal diseases include:

  • Poor air circulation
  • Overcrowding
  • Excess moisture on leaves
  • Weakened immune systems
  • Stress or injury to plants
  • Lack of good sanitation practices

If left untreated, some fungal diseases can seriously damage or kill plants. That’s why it’s important to take preventative measures to avoid fungal problems in your garden.

How Epsom Salt Works Against Fungus

Epsom salt is thought to help prevent plant fungal diseases in a few key ways:

  • Increases magnesium levels – Magnesium is believed to help strengthen plant cell walls. This can make plants less susceptible to fungal infection.
  • Improves plant health – The magnesium and sulfur in Epsom salt serve as plant nutrients. This may help plants better withstand disease pressure.
  • Changes soil conditions – Some studies have found Epsom salt makes soil less hospitable for fungal growth.
  • Has antifungal properties – There is some evidence magnesium sulfate may have antifungal activity in its own right.

Researchers have found that spraying Epsom salt solutions directly onto plant leaves can provide anti-fungal effects. The foliar application allows the magnesium and sulfur to be rapidly absorbed into plant tissues.

However, it is unclear exactly how and why Epsom salt repels fungi. The modes of action are still being investigated by scientists.

Studies on Using Epsom Salt Against Fungus

A number of scientific studies have analyzed the effectiveness of Epsom salt for controlling different plant fungal diseases. Here is a sampling of results:

Tomato Early Blight

– A 2011 study tested different Epsom salt concentrations against early blight infection caused by Alternaria solani in tomatoes. The 2% Epsom salt solution was most effective, reducing disease severity by nearly 75%.

Pepper Powdery Mildew

– Researchers in Iran tested Epsom salt against powdery mildew in peppers caused by Leveillula taurica. All concentrations between 0.5-2% significantly reduced disease intensity and increased fruit yield.

Zucchini Fusarium Wilt

– Scientists applied Epsom salt to soil to control a fungal wilt disease affecting zucchini plants. They found it suppressed the growth of the pathogen Fusarium oxysporum.

Grape Gray Mold

– Winery studies found foliar sprays with magnesium sulfate solutions decreased gray mold rot on grape clusters caused by Botrytis cinerea.

Wheat Seedling Blight

– One experiment showed that soaking wheat seeds in Epsom salt improved resistance against seedling blight diseases caused by Fusarium fungi.

So in most studies, Epsom salt provided some level of fungal protection, though efficacy varied based on disease type, plant species, and application method. The positive results support the potential for using Epsom salt to prevent plant fungal problems. However, there needs to be more research into the most effective practices.

How to Use Epsom Salt for Plant Fungus Control

If you want to use Epsom salt for preventing fungal diseases in your vegetable garden, flowerbeds, or houseplants, here are some general guidelines:

Foliar Sprays

Mix 1-2 tablespoons Epsom salt per gallon of water. Spray this solution directly on plant leaves, covering both top and underside of leaves. Reapply every 7-14 days as a preventative fungicide. Be sure to test on a few leaves first to check for phytotoxicity before spraying entire plant.

Soil Application

For potted plants, mix 1-2 teaspoons Epsom salt per gallon of soil. Repot plants using this amended soil. For in-ground plants, sprinkle 1/4 cup per 10 sq ft in garden beds. Work into top 3-6 inches of soil. Reapply 2-3 times per season.

Seed Soaks

To protect seeds against early fungal infection, soak seeds for 12-24 hours in a solution of 1-2 tablespoons Epsom salt per gallon of water before planting.


Add Epsom salt to your hydroponic nutrient reservoir at a concentration of 1-2 teaspoons per gallon of solution. This will provide constant magnesium and sulfur availability to your plants.

Always consult specific Epsom salt guidelines for the plants you are treating. Start with minimal concentrations and increase gradually as needed.

Risks & Precautions When Using Epsom Salt

While Epsom salt is generally safe, take these precautions when using it in your garden:

  • Test on a few leaves first to check for salt burn. Start with minimal concentrations.
  • Avoid applying during peak heat and sunlight to prevent leaf scorching.
  • Don’t use more than the recommended application rates.
  • Rinse edible plants well before consuming if treated with Epsom foliar sprays close to harvest.
  • May cause magnesium buildup and salt stress in soils. Flush soil as needed to prevent excess accumulation.

Also, Epsom salt should be used as part of an integrated pest management plan. Use proper horticultural practices to encourage healthy plant growth and prevent disease establishment.

Epsom Salt Fungus Control Considerations

Before relying solely on Epsom salt for fungus issues, keep these factors in mind:

  • Epsom salt works best as a preventative treatment, not against established or severe fungal infections.
  • It may help suppress certain fungal diseases but does not cure them.
  • Repeated applications are needed since it washes off plants in rain or watering.
  • Benefits can depend on the individual plant species and fungus involved.
  • It’s just one possible component of an integrated pest management plan.

Epsom salt has its place in gardens as an occasional soil amendment and supplemental foliar spray. But it generally works best alongside other organic fungicides and preventative measures. It should not replace chemical fungicides completely in cases of serious plant disease. Work with your local extension office for fungal disease recommendations specific to your area.


Epsom salt deserves consideration as an organic treatment to help deter fungal diseases in gardens and on houseplants. Studies have demonstrated it can offer partial protection against certain plant pathogenic fungi when applied directly to leaves or soil. It appears to operate through multiple mechanisms: improving plant health and magnesium levels, altering soil conditions for reduced fungal growth, and potentially having some intrinsic antifungal properties. However, Epsom salt is not a silver bullet solution. It performs better under some circumstances than others and has limitations like any other fungicide. With judicious use integrated into an overall disease management approach, Epsom salt can be a beneficial supplement to help reduce risks of plant fungal problems. But further research is still needed to refine best practices for utilizing Epsom salt against various fungal pathogens.