Wooden Bowl Full Of Epsom Salt
epsom salt 1
(Image credit: Diane Macdonald)

Many garden helpers can be found in our cupboards. Using Epsom salt for plants, for instance, has a long tradition. We’ll explore in this article some reasons that gardeners use Epsom salts in plants, as well as some reasons not to.

Using Epsom salt as plant fertilizer may improve flower blooming and enhance a plant’s green color. It can even help plants grow bushier. Epsom salt for garden use provides certain nutrients, but some gardeners claim it has other attributes as well.

 There is some indication that using Epsom salt as plant fertilizer in combination with other nutrient applications is useful. But what about the other claims such as enhanced germination and preventing blossom end rot? Let's explore.

Is Epsom Salt Good for Plants?

Epsom salt is a naturally occurring mineral salt that contains magnesium sulfate (magnesium and sulfur) and oxygen. It is very soluble in water and quickly releases the magnesium and sulfur, two key essentials for good plant growth.

While it may be beneficial to apply Epsom salt in plant soil, its quick solubility means it will rapidly leach past the roots, possibly bypassing the plant’s ability to uptake the nutrients.

Epsom salt’s magnesium and sulfur are only secondary nutrients for plant health and aren’t needed in the same quantities that nitrogen, phosphorus, and potassium are for development. A slow release formula containing all these micro-nutrients would give plants an overall better balance of nutrients and minerals.

However, because of its magnesium properties, Epsom salt supports the delivery of these other needed nutrients to plants’ roots, and also helps them generate chlorophyll, which is vital for photosynthesis. It’s worth knowing that magnesium and calcium ions compete for plant absorption. The more magnesium there is in soil, the less calcium is drawn into the plant.

Some Purported Benefits of Using Epsom Salt

In addition to helping with nutrient delivery to the roots of plants, Epsom salts have been touted for other garden uses, but the claims may not all be supported by facts.

Some gardeners claim using Epsom salt for plants can prevent blossom end rot which is caused by a lack of calcium in the soil. However, Epsom salts do not contain calcium and can therefore not prevent blossom end rot. In fact, using Epsom salt can exacerbate the problem.

However, plants that need an extra boost of magnesium may benefit from Epsom salt to some degree. These can include roses, tomatoes and peppers, and especially plants that are growing in containers. If your soil becomes depleted of magnesium, adding Epsom salt will help and, since it poses little danger of overuse like most commercial fertilizers, you can use it safely on nearly all your garden plants.

Other claims are that Epsom salt enhances seed germination and growth, reduces pests, and increases flowers and chlorophyll production. There is no evidence that the salts increase germination. Plant growth is driven by the proper amount of macro and micro nutrients.

As to pest reduction, there are no scientific studies that recommend this approach over others. Plants that appear to have more flowers and greener leaves due to Epsom salt application may be healthier because they were in a magnesium deprived site.

What Plants Don’t Like Epsom Salt?

If any plant declines after the addition of Epsom salts, it is likely due to toxicity. Magnesium toxicity is rare but not unknown. In most regions, magnesium deficiency is unheard of, and the addition of Epsom salts has the capacity to saturate the site in the micro nutrient. 

Also, due to the extreme solubility of the salts, the excess percolates down through sandy soils, past the roots. That means it is not utilized and instead, joins the water table and eventually the wild waterways creating a possible pollution hazard. When applied as a foliar spray leaf scorch can occur. 

Epsom salt use is also linked to root diseases in sugarcane and an increase of apple bitter pit, which makes apples unpalatable.

How to Use Epsom Salts for Plant Care

Providing magnesium in poor soils is the only bonafide use of Epsom salts in the garden. But if you want to give it a try, be sure the salts are diluted in water. As a general rule, 2 tablespoons (30 mL) of salts per gallon (3.8 L) of water is best, and only one or two applications per month. 

It may be applied as a foliar spray or added directly to the roots. As a spray, apply in the morning or evening. As a drench, prevent toxicity by using the mixture only if a soil test indicates a deficiency of magnesium.

When diluted with water, Epsom salt is most easily taken up by plants when applied as a foliar spray. Most plants can be misted with a solution of 2 tablespoons of Epsom salt per gallon of water once a month. For more frequent watering, every other week, cut this back to 1 tablespoon (15 mL).

With roses, you can apply a foliar spray of 1 tablespoon per gallon of water for each foot (31 cm) of the shrub’s height. Apply in spring as leaves appear and then again after flowering.

Overuse of Epsom Salt in the Garden

In most cases, nothing bad will happen if you use too much Epsom salt, but it does have the potential to pollute groundwater through leaching. Further, it can cause leaf scorch if not properly diluted, and can inhibit the uptake of calcium. 

Toxicity would be most common in container plants. Some experts feel that overuse of Epsom salts on plants is simply an inefficient way to support nutrients and a waste of a soothing bath soak.

Nikki Tilley
Senior Editor

Nikki Tilley has been gardening for nearly three decades. The former Senior Editor and Archivist of Gardening Know How, Nikki has also authored six gardening books.

With contributions from