Updated March 2022
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Buying guide for Best weed killers

No one likes the look of weeds in a lawn, flower bed, or vegetable garden. Beyond the lack of visual appeal, weeds steal valuable nutrients and sunlight from the plants you want to grow. Killing the weeds can help your other plants stay healthier.

It’s tough to pull stubborn weeds, and it’s frustrating when the root breaks in half, leaving the weed to grow back later. Instead, you can apply a weed killer, which uses chemicals to kill the weeds over time.

With so many different brands and types of weed killers on the market, picking the right option isn’t easy. Arming yourself with some key information will help you find the right weed killer for your situation.

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Weed killers use a chemical to attack an enzyme found in plants, breaking down the plant’s structure.

How weed killers work

Whether you use a powder, granular, liquid, or gel weed killer, the products all tend to work in a similar manner: the chemicals in the weed killer stick to the leaves of the weed, which then absorb the chemicals.

Once the plant absorbs the weed killer, the chemicals destroy the weed’s structure. The weed carries the chemicals to its root system, too, hastening the demise of the weed. You’ll notice spots and browning on the leaves a day or two after applying the weed killer. The plant will begin to droop one to three days after application. The plant should die three to seven days after application.

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Expert Tip
To ensure the weed killer only targets the weeds you want to kill, spray on a windless day.

Where to use weed killers

Some weed killer products will kill any kind of plant, not just weeds. Sometimes, you may want to kill weeds in an area but not the other plants growing there. For example, you might want to kill the weeds in your lawn while keeping the grass healthy.

Manufacturers have created a host of different weed killer products aimed at keeping certain plants safe. Other products will eliminate all plants, including weeds.

All weeds

If you want to kill all weeds, grasses, and other plants in a large area, choose a product designated for grass-killing. However, apply it carefully or it could kill nearby plants you’d like to protect.

"Certain weed killer products are sold concentrated, meaning you must mix the chemicals with water before application."

Lawn protection

Some types of weed killers, such as granular and powder, do not kill grasses, even if they come in contact with them. The chemicals in these products only stick to broadleaf plants. You can apply these weed killers to dandelions in your lawn without harming the grass.

"If you have a certain type of weed you want to kill, read the instructions. Each product includes a list of the weeds it kills."

Garden protection

Because most flowers and vegetables have broad leaves, using a weed killer in a garden is tricky. The chemicals will destroy broadleaf flowers and vegetables just as easily as weeds.

Your best option is to use a weed and grass killer product but apply it carefully. A gel type of weed killer works well in this case. Or use a sprayer very precisely on a day with no wind.

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Did you know?
Depending on the weed killer, you will have to wait a few days to several months to plant anything new in the area after application.

Woody plants

The most powerful types of weed killers work on woody plants, such as brush or ivy. These weed killers will also kill any other types of plants, such as broadleaf weeds and grasses. You want to apply this type of weed killer very carefully. Avoid using it on a windy day.

Weed killer application

Manufacturers have created a host of options for applying weed killer products. Some of these methods are more precise; others allow you to apply the product more quickly. Some weed killer containers are sold with the application device attached. Others require you to supply your own application device.

  • Sprayer: You apply most liquid weed killer products with a sprayer. If you’re applying the chemicals over a huge area, you might use a large sprayer pulled behind an ATV or lawn tractor. For smaller applications, you can carry a container and hold the sprayer in your hand. Air pressure feeds the liquid into the sprayer, and you press a trigger to apply the liquid.

  • Spreader: You use a drop spreader to apply powder or granular weed killer products. This is a common way to quickly apply fertilizer and weed killer mixed together on a lawn or other large area. Spreaders don’t work for applying weed killer to individual weeds.

  • Direct: You apply some of the newer weed killer gels directly by “painting” it onto the leaves.

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Expert Tip
Consider a gel weed killer if you need to precisely apply the chemical in a flower bed.

Weed killer prices

Comparing the costs of different liquid weed killers can be a challenge. Even if two products ship in the same container size, the weed killers may be nothing alike. When comparing prices, calculate the cost per gallon of ready-to-use weed killer. For concentrates, calculate the cost of the concentrate based on the number of gallons of diluted product you can make. Then compare that amount to the ready-to-use product.


For concentrated weed killers, you must add water to dilute the chemical before application. This gives you a better price per ounce than it may appear initially because you’ll get more applications per bottle than with a product that already contains water. Note that you’ll have to supply your own sprayer, adding another $10 to $25 to the cost, but you can use the sprayer dozens of times if you care for it properly.

Price: Concentrated products cost roughly $3 to $10 per gallon diluted.

"Most weed killer spray nozzles have different settings. Pick the best one for your application needs."


A ready-to-use weed killer requires no dilution with water. Most of these containers have a sprayer or other application apparatus built into them, further simplifying the application. Gel products fit into this category. You will pay extra for the convenience of a ready-to-use product.

Price: Ready-to-use weed killers cost roughly $8 to $20 per gallon.

Powder and Granular

Because powder and granular weed killers also include fertilizer, they’re used for a different purpose and not really comparable to liquid weed killers when it comes to price.

Price: Powders and granular products cost about $5 to $12 per 1,000 square feet of lawn.

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Especially tough weeds may need more than one application of weed killer.


Q. How will I know if the weed killer is working?
Most weed killer products show progress within several hours, although some require up to 24 hours. When the weed killer is working, you’ll notice brown spots on the weed’s leaves, and the plant will droop and appear unhealthy. Check the label on your weed killer product for the exact period of time between application and results.

Q. Should I apply weed killer before it rains, after it rains, or wait for a dry day?
All weed killers are a little different, but most sprays are best applied on hot, dry days. Because it’s difficult to predict the weather, you may inadvertently apply the weed killer right before it rains. For most weed killers, rain won’t wash off chemicals that have been on the weeds between 30 minutes and a few hours. Read the instructions for more specific information.

Q. Are weed killer products safe?
As long as you follow the instructions, you can use these chemicals safely. You should avoid prolonged exposure to skin for most of these products. Don’t let the chemicals splash into your eyes. And don’t ingest the chemicals. As long as you follow the instructions, kids and pets typically can play in the area a few hours after application.

Q. Will weed killers prevent weeds from growing back in the future?
Some weed killer products eliminate the weeds that are growing now, but they don’t keep more weeds from springing up later. Some products are designed to apply a barrier that stops new weeds from starting. Carefully read the instructions and recommended uses for any weed killer you’re considering to find out how it works on future weed growth.

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