Epsom Salt for Plants: 8 Ways to Use This Healing Mineral In Your Garden

You probably already have a package of Epsom salt hidden beneath your bathroom sink and haven’t given it much thought. It’s a relaxing addition to bath time, especially if you’ve got sore muscles—but did you know you can also use it in your garden? 

This multi-use mineral can make a world of a difference when used as fertilizer on both indoor and outdoor plants. There are some caveats, though. Here’s what you need to know.

What Is Epsom Salt?

Epsom salt isn’t really a salt because it doesn’t contain any sodium chloride. Though it has a similar shape to the salts you might use on your driveway after a snowstorm, it’s actually just crystalized magnesium sulfate, a naturally occurring compound made from magnesium, sulfur, and oxygen. The name comes from the city where it was discovered—an English horse-racing town called Epsom.

Is Epsom Salt Good for Plants?

The value of Epsom salt for plants lies in the magnesium content. While there’s not a lot of hard scientific evidence that Epsom salt is a miracle gardening product, it can help you grow healthier plants where a magnesium deficiency is present. Many gardeners find that the mineral helps plants produce stronger seedlings, more vibrant blooms, and vegetables dripping with flavor. 

Of course, it depends on the state of your soil—so you should probably get a soil test before diving in. Regardless, magnesium is essential for photosynthesis, and it can help plants absorb valuable nutrients (though you don’t want to give them too much of a good thing). 

How to Use Epsom Salt for Plants

Epsom salt has many uses in the garden—whether you’re growing traditional garden beds, a container garden, or an army of houseplants. In general, you’re going to want to use a DIY mixture of 1 tablespoon of Epsom salt per gallon of water, though some uses require dry crystals.

1. Give Your Seeds a Running Start

If you’re just beginning your garden, Epsom salt can help encourage germination. In this case, it’s less about how much Epsom salt you use for your plants and more about how you use it. There are a few different methods:

• Before seeding, put 1 tablespoon of Epsom salt into each seed hole.

• Before seeding, blend one cup of Epsom salt into every 100 square feet of soil.

• After seeding, water with your DIY mixture (and again every month through the growing season).

2. Improve the Nutrient Intake of Your Plants

There is some evidence that the magnesium in Epsom salt can help improve your plant’s ability to absorb key nutrients by strengthening the cell walls. Though this may not make much of a difference if your plants aren’t already magnesium deficient, try watering them twice a month with your DIY mixture. If you're feeding shrubs like azaleas and rhododendron, sprinkle 1 tablespoon of Epsom salts around the roots every two to four weeks.

3. Prevent Root Shock In Repotted Plants

All container gardeners know that repotting a plant is always a risk. Roots take time to acclimate, but Epsom salt can help your plant adjust. Apply your DIY mixture to the roots of your newly potted plant to stave off root shock.

4. Boost the Color of Your Blooms

Epsom salt is a great addition to your spring or fall flower beds because it can help produce larger, more vibrant blooms—especially if you’re dealing with a magnesium deficiency. In this case, Epsom salt works best if you spray it on the foliage. For each foot of plant height, use 1 tablespoon of Epsom salt mixed with 1 quart of water.

5. Add Flavor to Your Fruits and Veggies 

Epsom salt can boost the flavor of all kinds of fruits and vegetables—but it works best with plants that need a lot of magnesium like tomato and pepper plants. For the tastiest peppers and tomatoes, put 1 tablespoon of Epsom salt in the bottom of each hole before planting, then spray the foliage with your mixture every week. For other fruits and veggies, simply water with your DIY mixture.

6. Banish Pests—Especially Slugs and Snails

Want to banish the worst garden pests but avoid harsh pesticides? Try Epsom salt. To get rid of snails and slugs, sprinkle a ring of Epsom salt around the base of your plants. To get rid of other pests, spray the foliage with a mixture of 1 cup Epsom salts per 5 gallons of water.

7. Strengthen Your Rose Bushes

Roses are another plant that needs a high level of magnesium. You can spray the leaves of an established plant with your DIY mixture as soon as it starts to leaf and again when it flowers. If you’re planting new roses, give them a boost by adding 1 tablespoon of Epsom salt to the bottom of each hole before planting and layering with mulch.

8. Grow a Lush Lawn 

If your soil lacks magnesium, a lush lawn is only a sprinkle of Epsom salt away. Use a garden spreader to apply 3 pounds of Epsom salt for every 1,250 square feet of lawn, then water your lawn to dilute the salts.

Epsom Salt Risks

It’s also important to wear gloves because you can absorb magnesium sulfate through your skin. Not all Epsom salts are safe for humans—and some even have a laxative effect. Use agricultural-grade Epsom salts (the Epsom salt for plants) outside only. If you want Epsom salt for your bathtub, reach for a brand marked “USP” that’s safe for human use.

Epsom salt does pose a small risk to plants too, even though it’s a lot easier to burn your plants with chemical fertilizers. Always consult a local landscaper or soil testing service near you before making soil amendments. At the very least, Epsom salt won’t make much of a difference if your soil isn’t already magnesium deficient.