How to Use Salt to Kill Weeds

salt shaker tipped over on a table with the word "salt" written in the spilled salt

How do you use salt to kill weeds in your garden? Mix 1 gallon of water with 1 cup of table salt. On a sunny, dry day, spray the mixture on the weed’s leaves and stems. 

Salt is an effective weed killer but a dangerous one. It can sterilize soil, making it impossible to grow anything for years. If you use it, do it sparingly and with great care. We will explain the proper use of homemade salt herbicide, its risks, and the results to expect.

How to use table salt as a weed killer in a water solution

Spraying Weed Killer Onto Weeds
dean | Adobe Stock | License

A saltwater solution is easier to spread uniformly over the weed’s leaves and stems than dry salt. Because of the lower salt concentration, it’s also safer for the soil if some of the solution lands on it.

The saltwater herbicide recipe

To prepare a saltwater herbicide, you need:

  • 1 cup of table salt (sodium chloride)
  • 1 gallon of water
  • Spray bottle 

Add the table salt and water to the spray bottle and stir until completely dissolved. 

What can you mix with salt to kill weeds? You can tweak the recipe to improve the results:

  • Add a tablespoon of liquid dish soap per gallon of solution. Soap is a surfactant and improves surface contact. It’s especially useful on leaves with a waxy protective coating.
  • Dissolve the salt in boiling water instead of cold water. It makes it easier to kill the foliage of mature weeds.
  • Dissolve the salt in 1 gallon of vinegar (acetic acid) instead of water. Vinegar breaks plant cell membranes, speeding up dehydration.

Do you need protective equipment? Unlike chemical herbicides, salt weed killers are non-toxic for humans and pets and can be applied with minimal protective equipment. However, if you accidentally spray saltwater on your skin, wash it before it can dry the skin.

Safe vs. effective salt concentration

How much salt should be used in a weed-killer solution? Is 1 cup of salt enough? One liter of seawater contains 35g of salt — about 130g per gallon. When sea storms reach inland, this concentration is enough to leave behind browned, damaged trees, shrubs, and gardens.

A cup of salt contains about 250g, so the recipe above has roughly two times the seawater concentration. This is a good place to start when controlling weeds in your garden. 

You can increase the concentration for stubborn weeds, but only when using it on pavement or driveways, away from fertile soil. Some recipes recommend a water-to-salt ratio of 3:1 or 2:1, meaning four cups of salt or more per gallon of water.

Spraying the leaves for a safer application 

You can apply a liquid salt herbicide in two ways. One is to spray the leaves and stems thoroughly, not the soil, using the solution as a contact herbicide. In this case, salt draws water from the plant cells and desiccates the sprayed parts. Leaves and stems wilt, turn brown, and die, but the roots are unharmed. 

It works best on:  

  • Young plants with undeveloped roots.
  • Annual broadleaf weeds such as purslane, lambs quarters, and ragweed.

Mature broadleafs and grassy annual weeds such as crabgrass and foxtail might require multiple applications. Perennial weeds typically survive contact weed killers and eventually grow new leaves. 

However, spraying only the leaves and stems is less risky for the soil. You can even use the solution with care near cultivated areas (around the lawn, flower beds, etc.).

Soaking the soil for better results

The second method involves pouring saltwater into the soil to attack the weed roots. Salty soil prevents plant roots from absorbing water, although it is available nearby. This happens due to osmosis — the natural movement of water from areas with a low salt concentration to areas with a high concentration.

A high amount of salt in the soil can even draw water from the weed’s roots, killing the plant by dehydration. 

But that’s not all the salt’s killing power. Dissolved salt separates into sodium and chloride ions, which are toxic to plants. 

“The dissolved sodium and chloride ions, in high concentrations, can displace other mineral nutrients in the soil. Plants then absorb the chlorine and sodium instead of needed plant nutrients such as potassium and phosphorus, leading to deficiencies,” explain Mandy Bayer and Geoffrey Njue from the University of Massachusetts. 

“The chloride ions can be transported to the leaves where they interfere with photosynthesis and chlorophyll production. Chloride accumulation can reach toxic levels, causing leaf burn and die-back,” they add, detailing how salt acts as a systemic herbicide.

Warning! This method is highly toxic to the soil and can ruin its fertility and structure for years. Only use it on driveways and paved zones, far from cultivated areas.

How to use dry salt as herbicide

moritz320 | Pixabay | License

Sprinkler salt on the ground around the plant. Spray a bit of water to help it dissolve faster. The dry salt uses soil moisture to dissolve completely and acts similarly to a saltwater solution, except much more aggressively. 

Since it involves applying 100% salt on the soil, it should only be used on weeds growing in pavement cracks, driveways, and walkways. Never use it on garden beds, flower beds, or lawns. 

How much dry salt should be applied? Studies show that 49g of granular salt per square meter causes severe phytotoxicity and death in weeds such as sourgrass. Treating an area of 3 to 4 square inches around a weed or two in your driveway amounts to about 1/5 of a teaspoon of fine table salt or a pinch of salt.

The best time for salt weed killer application

The best time to apply a salt herbicide is during a dry, sunny day. Salt is a natural desiccant that damages plant tissue by drawing water out of nearby cells. Heat and wind speed up the process and increase weed damage. High humidity and rainfall slow it down and reduce the effect by diluting or washing away the salt.

Type of salt that kills weeds

Can you use any type of salt to make a weed killer? Table salt is the most common option. It’s highly processed and stripped of minerals, and its fine texture makes it easy to dissolve. Both ionized and non-ionized salt can be used in herbicide solutions. A common household item, table salt is also affordable and easy to find.

You can also use rock salt or sea salt. Both are sodium chloride (NaCl) with different percentages of minerals, impurities, and textures. 

What about Epsom salt? Epsom salt is magnesium sulfate. While it can harm plants, you must apply huge amounts to kill weeds and risk damaging the soil. “Epsom salts are touted because they contain magnesium instead of sodium, but too much magnesium will interfere with phosphorus uptake,” says Sarah Bailey, state coordinator, UConn Extension Master Gardener Program.

In small amounts, Epsom salt is often used as a fertilizer for magnesium deficiencies rather than a weed killer.

The dangers of using salt weed killer in your yard

Salt is a natural herbicide, but this doesn’t make it safe for the environment. It’s a non-selective weed killer that damages any plant it comes in contact with, weeds and crops alike. 

When you decide to use salt as herbicide, you expose your yard to serious risks:

  • Damage to desirable plants. Saltwater can damage grass, vegetables, and flowers if the solution drifts during the application.
  • Killing soil microorganisms. Too much salt in the soil kills beneficial fungi, bacteria, earthworms, and insects, which has long-term effects on the ecosystem.
  • It can travel and damage planted areas. Unlike vinegar, salt doesn’t evaporate. It stays in the soil and travels around the yard with the water. 
  • Salt increases soil pH. Alkaline soil prevents plants from absorbing iron and other valuable nutrients. 
  • It can prevent seed germination. A high concentration of chloride in the soil can stop seeds from germinating.
  • It damages soil structure and functions. High amounts of sodium harden the soil, limit its ability to absorb and circulate water toward the roots and lead to soil crusting.
  • Salt-loving weeds might invade your garden if you increase soil salinity. 

What do you do if salt is on your turfgrass or crops? Wash the leaves and stems with water. Apply water generously to the soil to dilute and wash away the salt. 

Weigh the benefits and risks carefully and consider alternative solutions. Focus on preventing weeds by covering bare soil with mulch, turfgrass, or groundcovers. Consider other natural and organic weed killers and non-chemical methods such as hand-pulling and sheet mulching to eliminate sprouted weeds. 

FAQ about salt as a weed killer

Will salt kill weeds permanently?

Applied directly to the soil to damage the roots, salt can kill weeds permanently. It can even turn the soil sterile so that nothing will grow on it for years. Use with precaution.

How fast does salt kill weeds?

Leaves start to wilt in a few hours after being sprayed with a saltwater solution. Salt applied to the soil has to be absorbed and moved throughout the weed. It can take up to 10 days for the plant to show severe damage.

What are the signs of too much salt in the soil?

If your garden soil has high salt levels, you’ll notice a white or yellow-brown crust on the soil’s surface.

Leave the weed killing to the pros!

Using salt to kill weeds might seem easy and safe, but it’s not. Instead of exposing the soil to salt toxicity, leave weed control to professionals. Lawn Love connects you with the best local lawn care companies with just a click. Find your lawn care pro and enjoy a weed-free yard without the risk of bare, sterile soil!

Sources:

Main Photo Credit:

Sinziana Spiridon

Sinziana Spiridon is an outdoorsy blog writer with a green thumb and a passion for organic gardening. When not writing about weeds, pests, soil, and growing plants, she's tending to her veggie garden and the lovely turf strip in her front yard.