We Asked Gardening Pros If Epsom Salt Really Kills Weeds—They All Said the Same Thing

Using common household products like Epsom salt as a weed killer appeals to many people who want to avoid synthetic herbicides and garden more sustainably. But does this viral Epsom salt weed killer hack actually work? We asked horticultural experts to break down the science behind Epsom salt and explain what really happens if you use it on weeds.

What Is Epsom Salt?

Unlike table salt, Epsom salt is not sodium chloride. It is a naturally occurring mineral compound of magnesium and sulfur. Both are essential micronutrients that plants need for healthy growth, explains Kerry Smith, an expert in home horticulture at Alabama Cooperative Extension System.

Magnesium is a critical part of chlorophyll, which plants need to turn energy from the sun into energy. Sulfur helps a plant produce amino acids, proteins, and enzymes. While Epsom salt is not a significant form of nutrition for plants, it can provide a little of these essential nutrients. So, not only will Epsom salt not harm your weeds the way table salt would, but it may make them stronger if they happen to need magnesium and sulfur.

Using Epsom Salt as DIY Weed Killer

“Epsom salt is not a herbicide replacement,” says David Russell, an assistant extension professor of crop, soil, and environmental sciences at Alabama Cooperative Extension System. “There is no basis in science for using Epsom salt to kill weeds.” Epsom salt is also not registered or labeled as a pesticide.

Despite the lack of scientific evidence that Epsom salt works as a weed killer, many homemade weed killer recipes floating around on the internet recommend spraying a mixture of Epsom salt, vinegar, and dish soap on weeds to kill them. In this concoction, the vinegar does the work of weed-killing, not the Epsom salt, according to Campbell Vaughn, an expert in home horticulture at Alabama Cooperative Extension System. Vinegar burns and dries out the leaves of plants it touches, she says, and dish soap helps the vinegar stick to the leaves. Epsom salt plays no role in killing the weeds.

The Downside of Using Epsom Salt in the Garden

Although Epsom salt can be used as a fertilizer, it should only be used in small amounts and with caution. Putting too much Epsom salt on plants could harm them by disrupting the soil’s mineral balance and altering its pH. That’s true whether you use it as a weed killer or as a fertilizer. “Sure, you could kill weeds if you dump enough Epsom salt on them,” Russell says. “You can also kill plants by putting too much fertilizer on them."

Better Ways to Kill Weeds

Instead of using Epsom salt, experts recommend these alternatives for weed management:

Hand pulling: Pull those weeds out by hand. “Your hands and a shovel are the best herbicides out there,” Smith says. “Muscle is my go-to weed management tool,” Russell says. Pulling weeds by hand is a targeted, environmentally friendly method for getting rid of pesky weeds.

Weeding is also a great exercise. A 175-pound person can burn 180 calories by weeding for half an hour. Jogging for 30 minutes burns 250 calories, so weeding is good for you as well as your garden.

Mulching: Put a thick layer of mulch, like leaves or straw, on beds to suppress weed growth by blocking sunlight from reaching seedlings.

Herbicides: Use herbicides as labeled, Russell says. He stresses that a lot of scientific research and expertise go into formulating herbicides, and they’re safe when used as directed. Vaughn agrees. “Herbicides go through a rigorous process to get approved for public use,” Vaughn says. If you prefer not to use conventional herbicides, look for natural weed killers with the OMRI label, which indicates the product is compliant with organic standards.