Using Rock Salt as an Effective Weed Killer

For gardeners and homeowners fed up with pesky weeds rock salt can be an affordable and effective weed killing alternative to commercial herbicides. But before you swap out your Roundup for a bag of rock salt it’s important to understand the pros and cons of using salt as a DIY weed control option.

What Type of Rock Salt Works Best?

Not all salt is created equal when it comes to weed killing power. Table salt contains additives that make it unsuitable. Look for pure rock salt sometimes called halite that is at least 98% sodium chloride. Popular kinds include

• Solar salt: Evaporated from seawater and contains trace minerals.

• Rock salt: Mined from ancient seabeds and most pure.

• Ice melt salt: Coarse grains good for gravel driveways.

• Pickling/canning salt: Fine grains good for gardens.

• Water softener salt: Ultra pure pellets.

For maximum effectiveness, choose a coarse, fast dissolving salt with a high percentage of sodium chloride. The purer the salt, the better it will dehydrate and kill plants and their roots.

Why Salt Kills Weeds So Effectively

Salt is an effective weed killer because of its desiccant properties. When dissolved in water and absorbed by plants, the high concentration of salt causes dehydration. Salt draws moisture out of plant cells via osmosis, a process that continues until plant tissues are completely dehydrated, stopping metabolic functions.

Salt also creates a high sodium environment that is toxic to plants. It prevents roots from absorbing water and essential nutrients like potassium, magnesium, and calcium. Excess sodium can build up to lethal levels, leading to plant death. These effects make salt an effective herbicide.

Using Rock Salt to Kill Weeds

To use salt for weed control, simply sprinkle it generously on unwanted vegetation. Apply approximately 1/2 to 1 cup per square yard. Avoid windy days so the salt does not drift onto desired plants. As the salt draws moisture out of plants and soil, it will dissolve into a brine. This brine solution can penetrate roots to their full depth, killing the entire plant.

Reapply salt as needed on areas with persistent weeds. Moisture from rain or watering will eventually dissolve the salt and it will need to be reapplied. The amount needed and frequency depends on your climate. In dry regions, a couple yearly applications may suffice while wetter areas require more.

Areas like gravel driveways, patios, sidewalk cracks, and other hardscapes are perfect candidates for using salt as a weed preventer. But take care to avoid runoff into lawns and garden beds.

Pros of Using Rock Salt as a Weed Killer

• Inexpensive and readily available. A 50 pound bag costs just a few dollars.

• Provides effective and lasting weed control. Salt kills the entire plant.

• Minimal work required compared to weeding by hand. Just sprinkle it on.

• Not easily washed away by rain or watering like liquid herbicides.

• Can be used safely on patios, gravel driveways, and other hardscapes.

Cons of Using Rock Salt for Weed Control

• Damages concrete and metal over time due to salt corrosion.

• Can linger in soil for a long time, preventing planting or regrowth.

• Runoff can leach into lawns or gardens, damaging or killing plants.

• Rainfall can wash salt into drainage systems or contaminate groundwater.

• Can be harmful to pets who walk on treated areas. Avoid skin/eye contact.

• May not kill deeply rooted perennial weeds in one application.

How to Use Rock Salt Safely for Weed Control

To minimize potential downsides of using salt as an herbicide, here are some best practices to follow:

• Clearly define treatment areas and avoid scatter or runoff onto lawns and desired vegetation.

• Limit use to hardscapes like patios, gravel driveways, sidewalks, parking areas.

• Check local ordinances. Some municipalities prohibit salt use for weed killing.

• Sweep up excess salt after application so it doesn’t wash away.

• Use liberal amounts of water to rinse salt off pets’ feet after walking in treated areas.

• Wear gloves and avoid skin contact when handling pure salt. Irritation can occur.

• Cover nearby plants with tarps or plastic prior to treatment.

• Apply when dry weather is forecasted to limit salt spreading via water.

• Till soil in areas no longer wanted as hardscapes prior to planting to dilute residual salt.

• Alternate salt with vinegar or flame weeding instead of continual salt applications.

When used properly in appropriate areas, rock salt can be an eco-friendly, natural alternative to commercial weed killers. But be cautious of overuse and take steps to contain salt in designated zones. Combined with manual weeding and mowing, salt can be one more tool in your weed fighting arsenal. Just be ready to reapply as needed to maintain control.

Frequently Asked Questions About Using Rock Salt for Weeds

What’s the best rock salt size for killing weeds?

Opt for coarse rock salt grains rather than fine powder or pellets. Coarse salt will dissolve more slowly and cling to weed leaves better for maximum contact time and absorption.

Does table salt work for killing weeds?

Plain table salt is not as effective as pure rock salt. The additives in table salt like anti-caking agents allow it to dissolve too quickly. Opt for additive-free solar, pickling, or water softener salt.

Where can I buy inexpensive rock salt for weeds?

Hardware stores, home centers, and warehouse clubs sell affordable 50 lb bags of solar salt or water softener salt for under $5. Ice melt salt also works if pure enough.

What’s the best ratio of salt to mix with water for weed killing spray?

A salt brine of 1 cup per gallon of water, sprayed liberally on weeds, offers an easy pre-mixed weed killing solution. Or simply sprinkle dry salt directly on weeds.

Is rock salt safe for pets?

Ingesting high amounts of salt can be harmful to pets. Prevent pets from licking their paws after walking on treated areas by rinsing paws with water. Avoid scattering salt in actively used areas.

Does salt stain concrete or gravel driveways?

Over time, salty water runoff can corrode concrete, causing pitting or flaking. Use salt judiciously on driveways and clean up excess. Gravel is not affected but can hold salt and prevent plant regrowth.

Is salt or vinegar better for killing weeds?

Vinegar kills only top growth while salt kills the entire plant. But vinegar won’t linger in soil or have corrosion issues. Alternate these eco-friendly options as part of a comprehensive strategy.

How long does rock salt keep killing weeds?

With minimal rain, 2-3 rock salt applications per year will provide season-long control of weeds in gravel areas, sidewalk cracks and driveways. More applications may be needed in rainy climates.

Will salt kill grass or harm my garden?

Excess salt can definitely migrate into lawns and flowerbeds, damaging or killing plants. Take precautions such as tarps when applying salt in close proximity to desired vegetation.

Using rock salt is one more chemical-free way to manage weeds. When used carefully on hardscapes and gravel areas, it can significantly cut back on labor intensive weeding and provide lasting control. Just be mindful of proper application practices and storage guidelines to use this affordable DIY weed fighting tool safely and effectively.