8 Best Weed Killer For Lawns + How & When To Use

Unless you’ve tried them all, it’s hard to know the best weed killer to use on your lawn. Doing a search produces so many results that beginning to sort through them all is often intimidating or misleading. 

I had the same dilemma before I decided to test a few herbicides out for myself. After researching and reading case studies, testimonials, and customer comments, I settled on 15 products to review.

After a four-week run, I’ve narrowed down 8 products that I believe to be the best weed killer for lawns and that are worthy of your attention. 

Top Lawn Weed Killers

If you’re in a hurry, here are my top two recommendations:

roundup for lawns 160

Best Ready-To-Use

Roundup For Lawns Weed Killer Spray

Easy to use on large areas or for spot spraying. Sings of dying weeds within 12 hours of application.

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Best For Large Areas

Scotts Turf Builder Triple Action Weed Killer

Excellent weed-killing performance with the benefit of fertilizing the lawn too. Recommend applying with a spreader.

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Selecting A Weed Killer For Your Lawn

Selecting the right weed killer is complicated. It goes beyond comparing prices. You have to think about your specific lawn type, types of weeds, and the weed structure, not to mention how and when to apply it. So I’ll start there to help unravel the different types of weed killers and how to get the best results from each of them.

Contact Vs Systemic

Weed killers generally work in one of two ways, destroying weeds systematically or on contact. The systemic killers take time to work, as they infiltrate the entire plant. Contact killers, as their name suggests, kill on contact. Let’s take a closer look at the differences between the two and the benefits and drawbacks of each:

Contact Herbicides  

Contact herbicides damage only the parts of the plant they contact. I found that they rarely killed the root system, and as a result of this, the weeds will regrow. To get the best results with a contact herbicide, you need to thoroughly cover the plant, stems, and leaves. This gives the solution an opportunity to soak right through to the plant’s root system and provides more chance of the roots being destroyed.

Contact weed killers are suitable for small annual weeds or weeds that don’t have a deep taproot. However, you’re likely going to have to repeat the application the following year. The good news about herbicides in this category is they have a quick turn-around time. This means if you get good coverage, you’ll see results in about one to three days. 

Systemic Herbicides

Systemic herbicides are absorbed by the weed through stems, leaves, and roots. It is slowly transported throughout the weed’s cell structure causing irreparable damage, killing it from the roots up. They are ideal for destroying perennial weeds thanks to the way their active ingredients spread, making it easy to kill tubers, rhizomes, and root systems.

Unlike their contact counterparts, systemic herbicides go slow and steady to win their race. 

There are a couple of things to bear in mind when using systemic herbicides. Most importantly, they will kill everything they come into contact with. That includes any plants, trees, herbs, and lawn you might want to preserve, so only use them where you need to and be sure to cover up anything you want to keep while you’re administering this stuff. You also need to be mindful about using systemic herbicides in clay soil. The clay particles deactivate commonly found active ingredients such as glyphosate that are often found in this type of herbicide.

Residual Weed Killers

There is another type of weed killer that is not so common in domestic settings, and that’s residual weed killer. This product sits in the soil and has the long-term effect of preventing weeds from growing. In fact, it will prevent any vegetative growth from any plant, so they should be used with extreme caution and in my opinion, not at all suitable for home use.

Pre-Emergent Vs Post-Emergent

Weed killers are classified into two primary groups: pre-emergent and post-emergent herbicides. Knowing the difference and how to use them helps get the best results. So, here’s a deep dive into what you need to look out for:

Pre-Emergent Herbicides

Pre-emergent works before the seedlings emerge from their seed pod. Pre-emergent herbicides act by creating a protective seal around plant seeds, preventing them from germinating. Basically, they suffocate and eventually kill the seeds, and they are only effective on plants that sprout from new seeds annually, such as goosegrass and crabgrass.  They do not destroy perennial plants (think established quackgrass) due to their deep root systems.

I apply pre-emergent herbicides from fall through to early spring, just as the weather warms and plants begin to sprout, because they yield better results at temperatures below 60°F. Whether I use a granular form or a liquid that can be sprayed on totally depends on the weather forecast, size of the area being treated, and situation. The granules rely on water for activation, so when you are covering a large area, you’ll need to wait for a light spring rainfall or, if you have the capacity, use a sprinkler. 

Post-Emergent Herbicides

Post-emergent weed killers are formulated to target actively growing plants. Their active ingredients travel throughout the plant to kill the root system and eventually the entire plant. These are perfect to use once spring is in full swing and plants have begun growing, when it’s too late to use pre-emergent counterparts. 

The post-emergent variety of weed killers comes only in liquid or granular form. When using the liquid form, you will need to spray the product directly on the weeds. I always say it’s best to spray after the base of the weed is torn or cut because then the plant structure is open. This allows the active ingredients within the herbicide to penetrate deep within the weed system.

When using the granular form, spread the herbicide on the lawn and activate it with a lawn sprinkler system or, if your timing is spot on, a light rain shower. You will need to repeat this weed killer application throughout the growing season to keep perennial weeds at bay.

While it’s an extra chore when there are already so many other clearing jobs to do, it is well worth applying a final application in late fall to help prevent weeds from spreading seeds and growing once spring rolls around.

Organic Vs Synthetic Weed Control

The term ‘organic’ is an unofficial, lightly regulated word that references something natural. It involves using ingredients present in nature to make an herbicide with similar effects as its man-made chemical or ‘synthetic’ counterparts. 

Generally, organic herbicides are safer than synthetic weed control products. However, as Ohio State University reports, some ‘natural’ remedies can also be highly toxic. With that in mind, always exercise caution when selecting, using, and storing any weed control products, and read the label to familiarize yourself with all of the associated hazards that come with using these types of products.

Organic Herbicides

Organic herbicides range from homemade concoctions to pre-mixed, store-bought solutions. Homemade solutions are generally inexpensive, depending on whether you have the ingredients on hand or if you need to buy in. Store-bought solutions are often pricier than their synthetic counterparts since they contain natural ingredients that are not mass-produced. 


Organic varieties are generally safer to use in terms of causing harm to people and pets if spillages occur. This is because the ingredients they contain are mostly natural. I’d strongly advise against ingesting any type of lawn weed killer, however, and always seek medical advice if either spillages or ingestion occurs.


Unfortunately, organic herbicides can sometimes have limited effectiveness and may provide you with a false sense of security. Whilst they will have less of a detrimental impact on the environment, you may need to repeat applications to see the benefit. They’re slower to get to work, and they can be more expensive than synthetic products if you buy them ready-to-go.

Organic makes sense if you’re dealing with a stubborn broadleaf outbreak or you want a cumulative year-on-year kind of effect. For instance, a study at Iowa State University found that laying corn gluten products may prevent up to 40% of crabgrass from germinating during the first treatment. Ongoing treatment increases the effectiveness by up to 80% if used year on year. Organics also make sense if you reside in an area where synthetic herbicides are banned.

Synthetic Herbicides

Synthetic herbicides make up the majority of products on store shelves. These herbicides are chemical mixtures that kill a variety of weeds. Most synthetic herbicides are selective. This means you can apply them on your lawn to kill unwanted plants without harming your grass. 


The man-made chemicals in synthetic herbicides are designed to be more effective, particularly in quickly killing multiple weed types. Since these man-made ingredients are usually mass-produced, prices can remain relatively inexpensive. If you lead a busy life and want immediate results, then synthetics may be the best option.


Still, there are downsides, not the least of which is the potential risk posed to humans and pets and also the environmental impact that using these products leaves on the world around us. They will even harm some plants and wildlife if not used properly. Despite the risks, the market is still awash with synthetic herbicide options. It’s down to homeowners’, gardeners’, and landscapers’ personal preferences to select the right product for the job at hand.

Weed Types

You’re probably here because you aspire to have a perfectly manicured, weed-free lawn and are sick of the sight of weeds popping up here, there, and everywhere despite your best efforts to mow, pick, and dig to keep them at bay. Some appear periodically while other weeds seem to come and go as they please, shedding seeds as they go.

If any of this sounds familiar then you need to know that identifying the type of weed you want to eradicate from your lawn is crucial. Generally, weeds are classified by their structure, as well as germination periods and survival times. Identifying a weed based on its structure is one of the quickest and easiest methods used to decide what product you need to eradicate the weeds in your garden. Here’s a rundown of the most common weeds found in lawns and how to identify them:

Broadleaf weeds

These are some of the easiest weeds to spot in lawns because they look nothing like grass. They all have flat leaves with veins. They grow from a stem and many have flowers that usually attract pollinators. They can grow annually, biennially, or perennially, so staying on top of them is no easy task. Their growth rate is less vigorous in the winter, however, they can leave seeds in the lawn ready for sprouting new weeds as the weather gets warmer.

Some of the most common varieties of broadleaf weeds include dandelion, chickweed, wild carrot, and clover.

Dandelion and Clover
Dandelion and Clover

Grassy Weeds

Grassy weeds tend to be perennial and appear as clumps of grass that are a different shade of green or have a different texture to your lawn. Some are more prevalent in cooler weather while others grow more prolifically in the winter.

They easily become established in lawns due to their deep root structures. They can be spot treated with herbicide or dug up but successful removal will only be achieved if the entire root structure is removed. Any roots that remain will just begin growing fresh shoots and the problem will reappear.

The most common varieties of grassy weeds are Johnsongrass, goosegrass, and crabgrass.



Sedge weeds often get mistaken for grasses or rushes because of its attractive green, strap-like leaves and its love for damp conditions. They grow in patches, have course blades and an abundance of seed heads. Make no mistake, sedge is a troublesome and invasive weed that can quickly take hold of your lawn. The most common types of nutsedge weeds are nutgrass and yellow nutgrass.


Weed Life Cycles

Identifying the types of weeds on your lawn will help you to select the best herbicide for the job at hand. Weed classification based on when it grows during the year will then help you to understand the complexity of the weed’s root system and, ultimately, how best to destroy them. 

Herbicide selectivity weakens the weed to help remove the infestation from your grass. Therefore, with the weed type, use active ingredients best suited to eradicate unwanted plants on your lawn.

Annual weeds 

Annual weeds, which include chickweed and crabgrass, reproduce from seeds and have a life cycle of a year. 

Biennial weeds 

Biennial weeds, such as wild carrots, reproduce from seeds and have a life cycle of about two years. 

Perennial weeds

Perennial weeds (think along the lines of dandelions, Johnsongrass, and yellow nutsedge) overwinter through specialized underground structures like tubers and rhizomes over a number of years. 

Weed Killer Composition 

The higher the percentage of active ingredients, the stronger the herbicide. 

The ingredients section on the label lists all herbicides (active ingredients) and inerts (inactive ingredients) contained in the weed killer. The label also indicates the percentage of herbicides and inerts in relation to the total volume. 

The percentage of active ingredients dictates the amount of product to be applied on the lawn. It also dictates the effectiveness of a given product on its target weed.

Lawn Size

Besides the types of weed, think about the size of your lawn. Normally, herbicides are sold in ready-to-use liquid, concentrate, or dry form. The formulation affects their land coverage and how quickly they get into action.

Concentrate herbicides are suitable for large lawns but they’re expensive. However, you do dilute them down, so don’t be fooled by the bottle or packet size. Be sure to check out the area coverage for price comparison.

Lawn Weed Killers Reviewed

I’ve taken the time to review and test each weed killer extensively so that I can bring to you an informed choice and you can get your green space looking it’s absolute best.

Knowing weeds in lawns as I do, I will continue to have the opportunity to re-test and update this list with the latest revisions and any new-to-market products. In the meantime, here’s my rundown of the best herbicides on the market right now.

1. Roundup For Lawns Weed Killer Spray

Best Ready To Use Spray

roundup for lawns
  • Ingredients: Glyphosate, Diquat
  • Targets: Broadleaf and Grasses     
  • Application:  Magic Wand Spray 
  • Formulation: Ready to use
  • Action time: 12 hours  
  • Rainproof: in 30 minutes 
  • Coverage: All areas
  • Use: Lawns, Borders, Walkways


  • Contains two powerful active ingredients that work together to target the eradication of weeds
  • Ready-to-use formula can be used as a spot control treatment or larger scale weed clearance
  • See results in as little as 12 hours


  • Not effective on all common varieties of invasive plant

RoundUp is a name synonymous with herbicides, so I had to test their selective weed killer for myself. Equipped with safety gear, I was able to give this a try both as a concentrated spot control formula for broadleaf weeds on my driveway by using the wand spray applicator, and by also diluting the concentrate into a backpack weed sprayer for wider coverage of grassy weeds and broadleaf weeds in my lawn.

Its two primary active ingredients — Glyphosate and Diquat — work together through absorption into the stem and leaves. This prevents formula from spreading to non-targeted plants. Glyphosate interacts with a unique enzyme found in plants, and Diquat gets absorbed by the soil to attack weeds at the root level. 

You can use RoundUp when weeds are actively growing, and when you haven’t mowed or trimmeed before spraying. The weather needs to be between 60 and 85°F. Apply when you don’t expect your lawn to be disturbed for several days after application. Lastly, while the soil should be moist, the leaves of the weeds should be totally dry.

This herbicide is ideal for clearing large lawns quickly and its performance was phenomenal. It killed the majority of the weeds within 17 hours and the dead weeds were easy to uproot a day after the application. 

On the downside, the results are not long-lasting, and I did begin to spot new weed sprouting up just a couple of weeks later. Also, some reviewers found that this RoundUp doesn’t do too well with out-of-control cactus, bamboo, and or as a moss killer. Hey-ho! You can’t have it all, I guess.

I got good results by using the recommended dosage of 6 fl. oz. of RoundUp concentrate with a gallon of water. It will need rinsing off any plant that you want to keep if you accidentally spill some. You should wait at least three days before planting spices, vegetables, and cactus after you’ve applied this.

Overall, it did its job, which isn’t surprising for a powerful, selective product from a top brand like RoundUp. View Roundup For Lawns Weed Killer Spray here.

In terms of safety, you’ll be able to continue your gardening activities 24 hours after the application, and this RoundUp product has been proven safe for livestock and humans.

Spectracide Weed Stop For Lawns
  • Ingredients:  Diquat dibromide
  • Targets: 470+ common weeds    
  • Application:  Uniform spraying 
  • Formulation: Ready to use  
  • Action time: 5 hours 
  • Rainproof: No
  • Coverage: 1-4 pints per acre  
  • Use: pastures, golf courses, parks, rangeland, lawns, cemeteries


  • It controls pest, diseases, and weeds – all in one 
  • Good value for money if you have a small area to weed
  • Won’t harm your lawn 


  • Not ideal for day temperatures above 90°F. 

Spectracide came pre-mixed with a spray attachment, making it really easy to use with no mixing, decanting, or messy pouring required. Performance-wise, crabgrass and dandelions began to wither two days after the application, while other weed types followed suit seven days after the application.

I sprayed in the late morning with the outdoor temperature around 53°F, a value between the recommended 45 – 90°F. I had also mowed my lawn two days before to help get better results.

I followed the directions to the letter and found that this product required more than one application to effectively kill the crabgrass and dandelions in my lawn. But, on the plus side, it didn’t harm any of my garden plants. Click here for Spectracide Weed Stop For Lawns

It is pricey for what you get but worth it if you just have a small lawn. It is known to kill over 400 varieties of weeds in as little as five hours. Plus, if you follow the usage instructions and obtain no results, you’re guaranteed to get your money back. 

 Southern Ag Amine 2,4-D Weed Killer 1 Quart
  • Ingredients: D-Dichlorophe and Dimethylamine
  • Targets: Broadleaf weeds 
  • Application: Spray
  • Formulation: Liquid Concentate
  • Action time: 8 hours 
  • Rainproof: No
  • Coverage: 1.5 oz per gallon to treat 400 sq ft  
  • Use: pastures, golf courses, parks, rangeland, southern lawns


  • Ideal for southern lawns 
  • Kills woody plants and broadleaf weeds indefinitely
  • Best value for your buck


  • Usage directions on the packaging are limited

I used Southern AG on a section of lawn with a variety of weeds, but mostly broadleaf. I used the ratio of 2oz. of concentrate, one gallon of water, and added dishwashing soap to serve as a surfactant. Some broadleaf weeds (clovers included) began to wilt and rot on the second day. Other weeds (mostly woody plants) didn’t exhibit death signs until after eight days.  

I realized early on that this weed killer works best at daytime temperatures between 70°F and 80°F. When the temperature exceeds 90°F, there is a chance the herbicide will harm your grass. 

Its key active ingredients (D-Dichlorophe noxyacetic acid and Dimethylamine salt) are absorbed into the stems and leaves of a plant. The herbicide then moves throughout the plant to kill the root structure. 

Besides killing a wide range of broadleaf weeds, Southern AG Amine 24-D is a great value for the money. You only need to use one to four pints of the product per acre. 

This herbicide is ideal for southern lawns because it helps control the overgrowth of weeds, grasses, and wildflowers present, especially during summer. It will also kill woody plants and any weeds on pastures, golf courses, and cemeteries. Check out Southern Ag Amine 2,4-D Weed Killer at Amazon.com

The results are visible within two weeks. When applying, cover the recommended amount of area without overlap. Also, prevent the herbicide from drifting to edible or other susceptible plants. 

Ortho Weed B Gone Hose End Spray
  • Ingredients: Various pre and post-emergent herbicides 
  • Targets: Most lawn weeds
  • Application: Uniform spreading 
  • Formulation: Granules 
  • Action time: 3+days  
  • Rainproof: Yes
  • Coverage: Up to 4000ft² 
  • Use: Northern lawns


  • Small pellets for easy application with a standard spreader 
  • Three triple-action technology 
  • Kills broadleaf weeds indefinitely 


  • The pellets are fluffy – get blown off by wind easily
  • High price tag
  • Doesn’t kill grassy weeds indefinitely  

Amongst the other weeds in my lawn, I needed a weed killer for dandelions and so I was eager to try this innovative solution. Once I got over the price shock, I calculated the number of granules I needed for my lawn.

I applied the granules after a morning dew on a day before a light rainfall. The outdoor temperature was roughly 72°F, which was between the recommended 60 – 80°F temperature. I had mowed the specific lawn section three days prior and bagged it to prevent the spread of dandelion seeds. 

It’s a bit of a military operation but the results speak for themselves. The dandelions and all the weeds were gone after just three treatments. 

Generally, this product is formulated for northern lawns. It has triple-action technology to kill, prevent, and feed. It kills broadleaf weeds, prevents the growth of grass weeds for four months, and feeds to build green, healthy lawns. 

Scotts Turf Builder is easy to use. First, calculate the lawn size using the Scotts My Lawn app to determine the amount needed to adequately cover the lawn. Then pour the measured amount into the spreader, adjust the settings as per the label requirements, and apply. Wait at least six to eight weeks between fertilizer applications. Find Scotts Turf builder at Amazon.com click here.

Scotts doesn’t recommend using Turf Builder on newly seeded areas. Instead, wait until after the fourth mowing. Also, when spraying, keep kids and pets out of the lawn and ensure they do not access the treated area for a day or two.

Ortho Weed B Gone Hose End Spray
  • Ingredients: Dimethylamine salt
  • Targets: Over 250 lawn weeds
  • Application: Uniform spraying 
  • Formulation: concentrate; ready to use; and ready to spray forms 
  • Action time: hours 
  • Rainproof: in one hour
  • Coverage: 32 oz. covers up to 16000ft² 
  • Use: lawns


  • Trusted brand 
  • Ready-to-spray formula and built-in nozzle attachment makes it an easy to use product 
  • Rainproof in 1-hour


  • Require more application rounds to get better results 
  • Does not destroy all weeds
  • The nozzle allows over-spray onto useful plants 

Ortho Weed B Gone is a selective herbicide product that is available to buy in different forms. You can buy it as a concentrate to use with the Ortho Dial N Spray or Tank Sprayer. Alternatively, buy it as a ready-to-use for spot treatments or a ready-to-spray formula that is ideal for broad application. It’s suitable for use on grassy weeds and broadleaf weeds, and can be used on your lawn and on pathways and driveways. Check out Ortho Weed B Gone here.

Having read some reviews about Ortho Weed B Gone giving inconsistent results, I decided to apply it on two separate sections of the lawn using the same procedures. It’s fair to say that I didn’t get the results immediately.

Initially, the grass remained green and weeds were flourishing. Two days in and weeds in one section had withered. By the third day, weeds in both sections had withered and began to rot. Bingo!

In the first seven days, some broadleaf weeds had died, grassy weeds discolored, and some dandelions were bouncing back to life. I had to repeat the application two times to get better results. Still, some 20% of the weeds seemed unfazed.

Just be careful to avoid spreading this product near any edible plants. It’s best to keep them covered when you are spraying or use the spot treatment instead. If you do manage to get the product on your precious crops, be sure to hose it off with water immediately.

I’ve noticed on some forums that gardeners report an earlier success when they combine the herbicide with other treatments, such as in-soil weed control and fertilization. Overall, the Ortho Weed B Gone is okay, especially if you’re patient enough to wait for its full effect. 

Preen One LawnCare Weed & Feed
  • Ingredients: zero-phosphorus 24-0-6 formula
  • Targets: Over 250 lawn weeds
  • Application: One Easy Application 
  • Formulation: Granules 
  • Action time: 2 weeks
  • Rainproof: N/a
  • Coverage: 9lb.cover 2500ft² 
  • Use: Lawns


  • Good value for money (9lb. covers up to 2500ft² lawn.)
  • Easy to use (no clumps, no dust in the granules)
  • Weed control plus fertilizer 


  • Did not kill some stubborn weeds like Creeping Charlie as I hoped 

I used Preen One LawnCare on a lawn section with a wide variety of weeds, including dandelion, creeping Charlie, creeping buttercup, and clover. This is a granular formula that needs to be applied with a rotary spreader and the conditions need to be just so. Make sure your lawn is relatively wet and there is no rain forecast for the next few days.

When I used this selective weed herbicide I noticed that the weeds didn’t die immediately. It took three to four weeks to see measurable results. Nonetheless, it was highly efficient. 

First, the herbicide targets grass seeds, stopping them from growing. Next, it kills clover, dandelion, and 250 other broadleaf weeds indefinitely. Finally, it slowly releases nitrogen to feed the useful grass for up to eight weeks. The zero-phosphate formula is proven to be eco-friendly – protecting waterways from vegetative growths in case of a runoff. See more details for Preen One Lawncare here

There are limitations to the type of lawn you can use this on. The manufacturer recommends that it is not used on carpet grass, dichondra, St. Augustine grass, or colonial bentgrass as it can result in irreparable lawn injury.

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  • Ingredients: Dimethylamine
  • Targets: Over 200 broadleaf weeds
  • Application: Spray
  • Formulation: Liquid concentrate
  • Action time: 8 hours 
  • Rainproof: No
  • Coverage : 32 oz. covers up to 8000ft²
  • Use: Outdoor, lawns


  • Good value for money (one 32 oz. bottle covers up to 8000ft²)
  • No measuring or mixing with the easy sprayer option 


  • Take weeks to see results 

Fertilome Weed-Out Lawn Weed Killer RTS was recommended by a good friend of mine who spent many years working as a landscape gardener. After doing a little bit of extra research, I discovered that the product promises to kill weeds fast so I had to add it to my list for trial.  

I did my calculations, added the required amount for my lawn section, and filled the sprayer to the right level. Typically, one gallon of RTS should cover up to 250ft². Use the ratio to add or reduce the amount per your lawn size. 

I did not see immediate results but within two weeks nearly all weeds on the section died. This included clover, dandelion, and the stubborn dollar weed. 

The herbicide can be used as a spot treatment or broad treatment. The spot treatment covers an area of up to 1000ft²/acre. However, it’s limited to residential turf grass. Click here to view Fertilome Weed-Out Weed Killer now.

Regardless of the type of treatment, the maximum application rate remains at 4 fl. oz. per 1000ft² per application. Always skip at least one month between applications. 

For best results, spray the herbicide during spring when the weeds are actively growing. You can also apply during fall to kill germinating seeds. Follow all the precautionary measures and observe the restrictions for your state.

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  • Ingredients: 3 patented herbicides 
  • Targets: Over 250 common weeds
  • Application: Comfort Wand Spray.
  • Formulation: Liquid concentrate
  • Action time: 24 hours
  • Rainproof: Within 1 hour
  • Coverage : 1000ft² basis
  • Use: Residential lawns


  • Rainproof within 1 hour upon dying 
  • Easy-to-use Comfort Wand applicator
  • Formulated especially for residential lawns 


  • Takes a long time to attain full effect 
  • Can be harmful to humans and pets when still wet 

I diluted 1/2 ounce of Ortho WeedClear concentrate to make a 24-ounce trigger-spray bottle. I used it for spot treatments on my lawn section comprising mostly dandelions and broadleaf weeds. 

Be sure to set the trigger to spray instead of a stream to preserve your product. 

The herbicide proved effective in knocking out broadleaf weeds with two shots. I could spot some measurable results in 12 hours or so, but it took two to three weeks for the full effect. Click here for Ortho Weedclear from Amazon.com

When applying, follow all the usage instructions lest risk harming your lawn. Also, it’s best to apply when the weeds are young and actively growing. 

How To Apply Weed Killer To Turf Grass

You must apply your weed killer correctly for the best results. Thus, before using the herbicide, thoroughly read its label and take note of: 

  • Shelf life 
  • Ingredients 
  • Target weeds
  • Consumption rates
  • Time of action
  • Recommended application method

Armed with the right information, ensure a precise dosing accuracy for an effective treatment. 

Before measuring and mixing the herbicide, check that the weed conditions meet the specifications on the label. For instance, are they small and actively growing? Are their root structures powerful and well-functioning? Are they among the target weeds listed on the label? 

Check the temperature of the soil and outdoor air. Generally, products work best in temperatures between 60 and 77°F. The subsoil housing the root structure should be at least 53°F or higher. 

If your lawn meets all the requirements, go ahead and apply the correct dosage while following the application method recommended by the manufacturer. 

Wear protective gear when applying herbicides. That includes protective clothes, respirators, rubber gloves, and goggles. Finally, clean the sprayer or spreader thoroughly to remove the product residue. Clean up and dispose of any disposable items.

Enhancing Herbicide Efficacy

Most herbicides work best on actively growing weeds. Consider applying 0.2-0.45% solution of ammonium nitrate days before applying the herbicide. The purpose of the fertilizer is to stimulate growth.

If you must apply the herbicide despite the weather forecast predicting rainfall within 24 hours, consider adding adhesive to the herbicide solution/granules. 

The adhesive of choice must be of biological origin to prevent the spread of toxic chemicals to cultivated crops and soil. 

Safety, Children, And Pets

The usage instructions note the level of toxicity and danger of a weed killer to pets and humans. All ingredients on the weed killer have varying degrees of toxicity. While most herbicides are mildly toxic to humans, they can endanger kids and pets. 

Keep herbicides away from kids and pets. When applying, ensure the kids and pets remain away from the lawn. Do not let them play on the lawn until the herbicide has dried up, or after the period recommended by the manufacturer. Read Non-Toxic Weed Killers Safe For Pets.

When To Apply Weed Killer To Lawns

The best time to control lawn weeds is when they’re actively growing, right before flowering, unless you’re trying to prevent weeds from appearing. In which case, apply a pre-emergent weed killer before the seeds begin to germinate.

Post-emergent herbicides work best when applied in spring or early fall. Apply selective post-emergent herbicides on a still day (wind speed < 6.5 mph), without rain forecast in 48 hours, and with an outdoor temperature between 60 and 77°F. Apply the herbicide at least three hours after watering, irrigation, or rain.

Apply the first dose two to three weeks before cultivation and the second dosage two to three weeks after to fully destroy unwanted plants. 

When working with pre-emergent herbicides, take note of the types of weeds and when they sprout. For example, summer annual weeds like goosegrass and crabgrass germinate in the fall and spring. Others, like henbit and chickweed, germinate in early fall. 

Thus, ensure your pre-emergent herbicide is applied before the target weed can sprout. 

If the weeds are overgrown, at a height of six inches or more, mow them first. Then wait until they’re 2.5-3 inches to apply an herbicide.

Do not use a pre-emergent weed killer on a newly seeded lawn.

How Long Does It Take For Lawn Herbicide To Work?

Herbicides have varying times of action. From my observation, some weed killers like RoundUp show results within hours, but it can take weeks to realize full effects. It takes somewhere between hours to three weeks to realize visible effects.

Verdict: Best Herbicide For Lawns

During my testing, I looked at herbicides that were easy to use and effectively killed multiple types of grassy and broadleaf weeds in a short span. 

roundup for lawns 160

Best Ready-To-Use

Roundup For Lawns Weed Killer Spray

Easy to use on large areas or for spot spraying. Sings of dying weeds within 12 hours of application.

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Best Granule Treatment

Scotts Turf Builder Triple Action Weed Killer

Excellent weed-killing performance with the benefit of fertilizing the lawn too. Recommend applying with a spreader.

My top pick is RoundUp Lawn. RoundUp was relatively easy to use, highly efficient, reliable, and affordable. It also exhibited measurable results in hours. 

The runner-up goes to Spectracide Weed Stop for Lawn due to its high efficiency. The herbicide kills over 400 weeds and exhibits visible results in five hours.  

Spectracide is followed by the Southern AG, one of the best value weed killers in the market. You only use one to four pints of the product per acre and kill a variety of weeds indefinitely. 

Lawn Weed Killer FAQ’s