How to Use Epsom Salt for Plants—And Why Gardeners Swear By It

Which plants benefit from epsom salt, how to use it and more

Author:
Laura Beck
Nov 4, 2024

You might have heard that you should be using Epsom salt in your garden. Many gardeners swear by it. In fact, it’s a popular way to treat all sorts of gardening issues, improve plant health and boost growth.

Before using Epsom on your plants, you should know how it works and which plants will actually benefit from it. You might not need to use it in your garden at all. Not every plant needs or even likes Epsom salt, and using it the wrong way could be ineffective—or even damaging.

We spoke to gardening experts to learn how to use Epsom salt. Read on to find out what we learned about how to keep your plants doing their best.

What Is Epsom Salt?

Epsom salt isn’t actually salt in the way we think of table salt. Its scientific name is magnesium sulfate, a naturally occurring compound made up of magnesium, sulfur, and oxygen.

“Epsom salt is a naturally occurring mineral compound found in Epsom, England,” said Jane Dobbs, expert gardener and gardening team lead at Allan's Gardeners. “It has unique gardening properties, unlike table salt. Two essential elements make up the salt—magnesium and sulfur, which play a big role in plant health. Epsom salt has been used for plant growth because of its simplicity, affordability, and effectiveness.”

Epsom salt comes in crystal form, similar to table salt, and it dissolves easily in water. You can find it in most pharmacies or grocery stores, and it's usually pretty inexpensive compared to other gardening supplements.

Epsom Salt for Plants

The main benefit of Epsom salt is its magnesium content, which is vital for plants to grow. When plants don't get enough magnesium, you might start seeing yellowing leaves, poor fruit production, or stunted growth.

“Plants love Epsom salt,” said Dobbs. “It gives plants a better chance of converting sunlight into energy because it provides magnesium, an essential component of chlorophyll. The sulfur in Epsom salt helps plants produce amino acids, proteins, and enzymes. When you use it regularly, seeds germinate better, nutrients absorb better, plants grow stronger, and blooms are more vibrant.”

If a plant’s soil is acidic or nutrient-poor, they might struggle to take in nutrients. Magnesium helps plants take in nitrogen and phosphorus, which they need for healthy growth.

When to Use Epsom Salt on Plants

Knowing when to use Epsom salt can make all the difference in your garden. If your plants are growing too slowly, or their leaves are turning yellow—it might be time to get out the Epsom salt.

“For plants to stay healthy, you've got to detect nutrient deficiencies,” said Dobbs. “Yellowing leaves are a sign of magnesium deficiency, especially between the veins, and new leaves are a sign of sulfur deficiency. Plants with these deficiencies may grow stunted, yield less, and overall be sick. It's easy to diagnose these issues early by observing plant behavior and appearance. Epsom salt is a good cure.”

You can also use it proactively on plants that will definitely need the extra magnesium, like tomatoes, peppers, and roses.

“Different plants need different amounts of magnesium,” said Dobbs. “Epsom salt boosts growth and fruit production in vegetables like tomatoes, peppers, and beans. Flowers, especially roses, bloom more vibrantly and have healthier leaves. Occasionally applying Epsom salt makes fruit trees and shrubs sweeter and juicier.”

You should use Epsom salt at the start of the growing season when plants are just starting to sprout. You can go on using it throughout the season if your plants are showing signs of stress. Just don’t go overboard.

What Plants Don't Like Epsom Salt?

While Epsom salt is great for certain plants, it’s not great for all of them.

“Most succulents and cacti don't need additional magnesium, since they thrive in nutrient-poor soil,” said Dobbs. “It can cause root damage if you use Epsom salt because you disrupt their natural nutrient balance.”

Plants that thrive in alkaline soil typically don’t need the extra magnesium and could even suffer if you add too much. Plants that grow in acidic soil might also react poorly because Epsom salt can make the soil more neutral over time.

“Sage, thyme, and oregano prefer slightly leaner soils, so adding Epsom salt can result in lush foliage at the expense of flavor, as these herbs get stronger essential oils in less nutrient-rich soils,” said Dobbs. “Carrots, radishes, and turnips need phosphorus and potassium to grow. An excess of magnesium can interfere with other essential nutrients, causing poor root growth. Epsom salt doesn't really work for these plants.”

You also want to avoid using Epsom salt on plants that are already getting enough magnesium. Adding more magnesium won’t help these plants, and Tammy Sons, founder of TN Nursery, said to never use Epsom salt at all “unless you have had a soil sample test and it is low in magnesium. An overdose of magnesium causes plant death.”

Can I Just Sprinkle Epsom Salt on Plants?

Sprinkling Epsom salt directly on plants isn’t the best way to use it.

“Never do this, always dilute in water,” said Sons.

The tried-and-true best way to apply Epsom salt is by dissolving it in water and using it as a spray or watering solution. This way you’re certain that the magnesium and sulfur are getting to the plants and the nutrients are distributed evenly.

Can I Put Epsom Salt Around My Tomatoes?

Tomatoes are one of the most common plants that benefit from Epsom salt. Tomatoes often deal with a lack of magnesium, especially when they’re grown in poor soil.

Sons said that Epsom salt should only be used on tomatoes “if the leaves look light and yellowish.”

If you do add Epsom salt, it can improve your tomato production, and also help tp prevent issues like blossom-end rot. This is a condition caused by the nutrients being out of balance.

Will Epsom Salt Kill Weeds?

Epsom salt isn’t usually used as a weed killer.

Doing so is “not a good alternative, too much unbalances the soil,” said Sons.

Although Epsom salt may kill your weeds, keep in mind that Epsom salt is used as a nutrient supplement, not a herbicide. You run the risk of throwing off the nutrients your plants are getting.

How Much Epsom Salt Do You Put in a Gallon of Water?

The standard ratio for mixing Epsom salt with water is about one tablespoon per gallon of water.

“You can spray this on the leaves for faster absorption or apply it directly to the soil,” said Dobbs. “For potted plants, use a lower concentration to prevent root burn.”

This mixture can be used to water your plants or as a spray. This is really useful if you want to give your plants a quick magnesium boost. Just spray the solution onto the leaves, and the plant will absorb it directly.