13 Best Post-Emergent Herbicides 2020 + Buyer’s Guide & FAQs

If there’s one thing that’s guaranteed to ruin a garden, it’s when it has been overrun with weeds.

And even if you’ve managed to put down one of these excellent pre-emergent herbicides, they can still slip through the cracks and spoil your landscaping.

Be it in flower beds, vegetable patches, on patios and driveways, along fences or across your lawn – life finds a way.

So, I’ve put together a review of the best post-emergent herbicides – for treating weeds and unwanted vegetation that has already taken hold and is visible through the soil.

A buyer’s guide and FAQ section will follow to help you choose the right product for your needs – and the needs of your garden.

There’s no place left to hide for weeds.

13 Best Post-Emergent Herbicides 2020

BioAdvanced Weed Control for Lawn

To start us off we have a combination of a pre-emergent and post-emergent herbicide. This hose applied product from BioAdvanced can cover up to 7,500 square feet, and when used as directed it will kill existing lawn weeds while not harming your lawn.

Once laid down, it will then protect the surface and prevent weeds from springing back up for six months. The 2-in-1 formula is easy to use and delivers season-long weed control that you can apply anytime from spring through to the fall, and it kills over 200 listed weeds, including dandelion and clover.

For the price, it’s one of the best post-emergent weed killers for lawns there is.

Pros

  • Excellent value.
  • Easy to use.
  • Great coverage.
  • Long-lasting protection.
  • Available in concentrate.

Cons

  • Mixed results.
  • Not as potent as dedicated post-emergent weed killers.
  • Initial results might take a long time.

Conclusion

A single-application pre and post-emergent herbicide might seem too good to be true, and it certainly looks like it works for some but not for others. Still, at this price, you could do a lot worse than give it a try.

Ortho Groundclear Weed and Grass Killer

This Groundclear product from Ortho is an OMRI listed herbicide for organic use and safe to use all-around your property. Upon spot treatment with the weed wand included (which is a highly accurate method of application), it gets to work immediately for visible results inside 15 minutes.

Use on patios, landscape beds, walkways, vegetable gardens and around trees and shrubs to keep your existing weed problems in check, and you can apply it at any time of year when weeds are actively growing.

Check this article for more great weed killers for driveways – but you can use this just about anywhere.

Pros

  • Highly rated and effective product.
  • Rainproof in two hours.
  • Safe for use around edibles.
  • Easy-to-use and direct.

Cons

  • Stubborn weeds likely to return.
  • Multiple applications might be required.
  • For smaller weeds, only.

Conclusion

If you need a fast, accurate, and certified organically safe weed killing option for spot treating individual weeds – then this could well be the product for you. Just don’t expect it to work miracles if your yard is a jungle.

Scotts Turf Builder Weed and Feed

Scotts need little introduction when it comes to lawn care, and this is their popular and well-known weed and feed product. It works as a pre and post-emergent herbicide, with a low percentage of 2,4-D that selectively attacks dandelions, clover, and other nuisance weeds.

With a weed-grip technology that combats the plants you can and can’t see, it’s a highly useful lawn feeder and protector that’s best applied in spring to thicken your desirable turf and crowd out the unwanted vegetation.

Probably the best granular post-emergent weed killer for lawns available.

Pros

  • Name to trust.
  • Highly rated.
  • Easy-to-spread.
  • Improved formula.
  • Excellent coverage.

Cons

  • Not fast acting.
  • Mixed results depending on the application/zone.

Conclusion

Another great product from the lawn-lovers, send those dandelions packing with Scotts’ Weed and Feed. And head on over to this article for some fascinating lawn mowing tips to really improve your green space.

Compare-N-Save Concentrate Grass & Weed Killer

The first (and certainly not the last) of our post-emergent weed killers to contain glyphosate, this Compare N Save offering certainly will save you a packet compared to the big-name brands.

One gallon of this stuff makes up to 85 gallons of lethal liquid death, and the 41% concentration of its active ingredient will be merciless to anything green in your garden.

That means you can cover over 25,000 square feet and see visible results between two and four days. There’s no residual activity, so ornamental treated areas can be replanted as soon as a day after spraying (but fruit and vegetable plots vary).

Pros

  • Outstanding price.
  • Potent formula.
  • Very highly rated.
  • Kills to the root.

Cons

  • Contains glyphosate.
  • Results can take time.

Conclusion

An excellent alternative to Roundup and similarly well-known brands, definitely worth a try. The aptly titled ‘Compare N Save’ lives up to its name.

Southern Ag CROSSBOW32 Weed & Brush Killer

Many landscaping professionals, farmers, or anyone who wishes to get rid of unwanted trees and brush swear by Southern Ag’s Crossbow product.

For use on rangeland, grass pastures, and non-crop areas, the 34.4% 2,4-D formula with added triclopyr leaves grasses unaffected but is deadly to the likes of blackberry vines, poison ivy, kudzu, creeping charlie and multiflora rose – as well as offering the ability to kill most annual and perennial broadleaf weeds.

Offering excellent coverage, with a variety of application methods, and good value for money, you can see why it’s the go-to nuisance tree and brush exterminator for the pros. One of the best post-emergent selective herbicides there is.

Pros

  • Very highly rated.
  • Name to trust.
  • Versatile use.
  • Commercial-grade.

Cons

  • It might be overkill for smaller residential areas.
  • Can take a while to work.

Conclusion

For ridding your yard or garden of unwanted trees and brush, this is your best bet right here. Give it a try for more stubborn growths, and check out this article for further advice on how to kill nettles if you’re struggling with that stinging bastard.

Southern Ag Amine 24-D Weed Killer

Following right on the footsteps of their Crossbow product, Southern Ag offers this 2,4-D weed killer – a highly potent option for killing broadleaf weeds – without damaging existing lawn turf.

Providing selective weed control for use in and around pastures, rangeland, cemeteries, parks, and golf courses – this is a professional product that you can use around your home (just be very careful in its application and avoid drift to desirable plants).

A full list of weeds controlled is included on the label, and the economical use means that you get a lot of bang for your buck with the quantity. Try one of these lawn aerators before use for the best performance and results.

Pros

  • Very highly rated.
  • Name to trust.
  • Controls a large variety of weeds.
  • Commercial-grade.

Cons

  • Might take up to two weeks to see results.

Conclusion

Probably the best post-emergent weed killer for Bermuda grass (that you want to keep), this broad-spectrum product is a great addition to any weed killing armory.

Green Gobbler Vinegar Weed & Grass Killer

I always try to include an organic, pet-safe weed killer if it’s compatible with the review, and the Green Gobbler is my go-to recommendation here.

Made with 20% industrial-strength vinegar, it’s four times stronger than traditional table vinegar, extracted from ethanol distilled from corn grain. With no glyphosate insight, you can kill weeds and grass all around your garden, as well as for commercial, industrial, and agricultural use.

No mixing is required and it’s ready right out of the container, and OMRI listed as safe around organics. And take a look at this review for more excellent pet-safe weed killers if you prefer not to use harsh chemicals in your garden.

Pros

  • Eco-friendly weed killer.
  • All-natural ingredients.
  • Easy to use.
  • Very highly rated.
  • Biodegradable.

Cons

  • Not for use on lawns.
  • Powerful smell.
  • Very acidic – don’t get it on your skin.

Conclusion

With a large fan-base and garnering a ridiculous amount of quality reviews, you could do a lot worse than try this planet-friendly option. I’m all for promoting the use of natural products in our gardens whenever we can help it.

Spectracide Weed and Grass Killer Concentrate

A return to more familiar weed killers now with this concentrated product from Spectracide. Able to eliminate poison ivy, clover, dandelion, and other listed weeds, it’s a potent formula that’s safe for use on patios, walkways, and around flower beds.

A non-selective herbicide, you can cover up to 6000 square feet when mixed with water and applied with a tank sprayer. Spectracide will kill to the root and you will see visible results within three hours, with the ability to replant in the treated area as early as the following day. And check out this article for more of the best weed killers for use around flower beds.

Pros

  • Name to trust.
  • Rainfast within 15 minutes.
  • Fast-acting.
  • Excellent coverage.
  • Very highly rated.

Cons

  • Not for use around edibles.

Conclusion

A popular, potent, and powerful post-emergent that will get the job done. Just be very careful around your desirable plants and consider protecting them with cardboard or plastic sheets.

Roundup Weed and Grass Killer

This Roundup Weed and Grass killer has a smaller percentage of glyphosate than some of its more potent products, but it has nonetheless garnered much praise for its ability to kill the toughest weeds and grasses to the root.

Available in a wide selection of quantities and application methods, this ready-to-use formula is fast and convenient, designed for use in and around vegetable gardens, flower beds, tree rings, and mulched beds, as well as on cracks in driveways, walkways, and patios.

Perfect if you want a weed killer that will kill everything with an instant and accurate application. This doesn’t mess about.

Pros

  • Very highly rated.
  • No mixing required.
  • Rainproof in 10 minutes.
  • Less harsh than other options.

Cons

  • Still contains glyphosate.
  • Mixed opinions regarding the applicators.

Conclusion

Although you’ll always get some folks unhappy with any weed killer dispensing method, this option from Roundup is a fast, effortless, and efficient solution for spot treating things you just want dead. Full marks for convenience.

RM43 Glyphosate Plus Weed Preventer

RM43 is a professional, popular, pre and post-emergent herbicide. If you want to clear an area of any plant life – and for it to stay clear – then this is the product for you.

One gallon will treat up to 17,297 square feet, and it will keep any treated area weed and plant-free for up to one year. Designed for use around fence rows, gravel paths, sidewalks, driveways, parking areas, and around farm buildings and barns, this is an agricultural-grade product that’s available for your use around your home.

The best post-emergent herbicide for crabgrass (or any grass for that matter) this will kill everything – so take great care when dealing out the death.

Pros

  • It works. Period.
  • Very highly rated.
  • Long residual effect.
  • Value for money.
  • Excellent coverage.

Cons

  • High percentage of glyphosate.
  • Results might take a bit of time.
  • Literally overkill for most residential areas.

Conclusion

When you’ve got to kill everything and keep the ground barren and bare – RM43 is the chemical of choice. Just try not to spray anywhere near desirable greenery – or you risk losing that, too.

PBI Gordon – Ornamec Grass Herbicide

Now, this was a late entry into the post-emergent herbicide review, as I stumbled upon it researching something that would kill Bermuda grass. This certainly does that, designed for the control of unwanted grasses in groundcovers, trees, and shrubs.

Nearly 500 species of plants can be brought to heel by using this “over-the-top” product from PBI Gordon.

A selective, post-emergent herbicide, it will control annual grasses such as panicum, goosegrass, crabgrass, foxtail, sandbur, and barnyard grass, as well as the tricky Bermuda grass that some people love and others will hate – depending on your location.

Apply anywhere grass weeds are crowding out your desirable plants.

Pros

  • Stops selected grass growing within 48 hours.
  • Rainproof in one hour.
  • Can be applied over the top of desirables.

Cons

  • Directions are confusing.
  • Not for use around edibles.
  • Can take a while for visible results.

Conclusion

A product specifically designed to target nuisance grasses, just so long as you follow the instructions to the letter (which isn’t as easy as you might hope). Also, read our article on the best weed killers for Bermuda grass if you’d like more options for controlling that trickster.

Roundup Weed and Grass Killer Super Concentrate

Our final Roundup product is the penultimate entry in this review and is one of the most potent weed killers in their range.

The purple-capped super concentrate contains 50.2% glyphosate, which is one of the highest you can buy and is marketed as the best Roundup product for widespread weed problems.  If you have a lot of stubborn plants to kill over a large area, then the buck stops here.

Designed for use in tank sprayers, this will rain liquid death down on anything green it touches, so be sure you know what you’re doing and where you’re applying it. You’ll see visible results within 48 hours.

Pros

  • Highly rated.
  • Very potent.
  • Rainproof in 30 minutes.
  • Excellent coverage/value for money.

Cons

  • Very high glyphosate concentration.
  • Controversial coverage in the media.

Conclusion

There’s no denying this stuff works for killing any plant life on or around you’re property – but it’s not having the best of advertisements with current events. As with any strong chemical – use at your own risk and take great care if you do so.

Monterey Remuda Concentrated Herbicide

Last but not least is this Monterey Remuda concentrated herbicide, also with a high concentration of glyphosate at 41%. It also contains a surfactant, which is a bonus for improving coverage and absorption by the plants it is targeted to treat.

For use in unplanted areas and around trees, shrubs, and flower beds, one pint of this stuff offers an impressive 320 gallons of potent herbicide that will cover a whopping 320,000 square feet.

Most effective when used in temperatures of 70 degrees and above, this is a commercial-grade weed killer for anyone deadly serious about plant death. A compression sprayer is recommended.

Pros

  • Kills everything.
  • Ready-to-use.
  • One application should be enough.

Cons

  • Results can take up to two weeks.
  • Expensive.
  • High glyphosate concentration.

Conclusion

A potent weed killer that offers outstanding coverage – probably best reserved for those with an extensive plant problem over large areas. You could always try one of these commercial weed whackers instead – but they will come back eventually.

How to Choose the Best Post-Emergent Herbicide

Spraying herbicide on dandelion

Below you’ll find plenty of tips and advice to assist you in choosing the right post-emergent herbicide for you.

How Post-Emergent Herbicides Work

The clue is in the name for post-emergent herbicides, and they’re designed to work after a plant has established itself and broken through the soil.

Post-emergent herbicides work best when the unwanted vegetation is actually growing.

How it does this depends on the individual product and the active ingredient it contains. It’s not one size fits all, and there is a huge variety of herbicides that attack weeds in different ways.

Post-emergents will contain a number of different chemicals or ingredients that are designed to inhibit plants and exterminate them. For more information, read this excellent, in-depth article on how herbicides work.

Advantages and Disadvantages of Post-Emergent Herbicides

The pros and cons of post-emergent herbicides are well documented, but let’s just briefly touch on them here for simplicity’s sake.

Their greatest asset is that they are very effective at what they do – particularly when it comes to the more potent weed-killing chemicals – such as glyphosate.

Certain products will burn down a problem weed in a matter of hours, and in a couple of days, it will be stone dead. For others, it might take a few weeks – but you should still get good results eventually.

Aside from this, they are very easy to use, with a variety of application methods available depending on where, what, and how much you’re treating.

Unfortunately, that’s where the advantages stop. Post-emergent herbicides are, with some exceptions, dangerous, toxic chemicals.

These formulas can cause a detrimental impact on the environment, not to mention to the people who use them, their children, and pets.

And unintentional spread can be difficult to control – especially when treating larger areas with a tank or backpack sprayer. Even the slightest breeze or misdirected application can cause a non-selective herbicide to come into contact with desirable vegetables, plants, and blooms.

Often a necessary evil, weed killers should be handled with great caution – and by people who know exactly what they’re doing.

But have a look at this article for how to get rid of weeds in a lawn without using chemicals. I always try to encourage more natural ways whenever possible.

Quantity/Coverage

Field of plants

As with all weed killers, the amount you purchase will depend on how much land you need to cover, or how large your weed problem is.

If you’re treating one or two weeds, you can use a spot treatment with a trigger or weed wand. This herbicide will likely come in a ready-to-use bottle.

For larger areas, a tank/compression sprayer or hose applicator might be called for. Often, a herbicide that is distributed in this manner will come as a concentrate – and require diluting with water.

A surfactant might be required – which is an additional liquid that is added to help break the surface tension between the weed killer and the target. Surfactants help the herbicide go further and be absorbed faster.

Either way, try to purchase quantities that you know you’re going to use. Herbicides have a shelf-life – and will become ineffective and wasteful if surplus to requirements.

Application Method

As previously mentioned, post-emergent herbicides can be dispensed in a variety of ways, and they come in the form of either liquid or granules.

Granular post-emergent weed killers are applied either with a dedicated spreader or by simply shaking the bag or box of product where you require.

The best liquid post-emergent weed killers are applied either with a trigger gun, a weed wand, a hose applicator, or a tank/backpack sprayer.

The method you choose will depend on the area you’re covering, the results you’re trying to achieve, and the type of weeds you’re attempting to treat.

Selectivity/Targeted Weeds

Like pre-emergent weed killers, their post-emergent counterparts can either be selective or non-selective when it comes to the plants they are designed to target.

Selective weed killers will only attack certain plant life. They’re best used in lawn care where you don’t want a herbicide to damage your existing turf grasses, but you do need it to clear undesirable weeds.

Non-selective weed killers will go after just about anything that’s green. They’re best used when you want an area completely devoid of any kind of vegetation.

Before making your purchase, you should know the types of weeds your preferred product is or is not going to kill. All too often mistakes are made and the wrong kind of herbicide is purchased for the wrong job.

When in doubt, check the label. All herbicides should list the plants that they will attack, so you know if you’re purchasing the right product for your needs.

And I’ve yet to see a better video than the one below to help you with weed identification.

Rainproofing and Persistence

Apart from the timing of application, perhaps the most notable difference between a pre and post-emergent herbicide is to do with how long it lasts in the soil.

It’s not always the case, but generally, a pre-emergent herbicide will last several weeks/months longer than a post-emergent.

While there are post-emergent herbicides that have lengthy residual times in the soil, for the most part, they don’t hang around. This is so you can be free to plant desirable foliage and flowers within a few days of application.

Aside from that, pre-emergent herbicides require water to be activated, whereas post-emergent herbicides will not be effective if they’re washed off their target plants.

There’s also a risk that surface run-off will carry potentially dangerous chemicals into water courses and unwanted areas.

Post-emergent weed killers, therefore, come with guidelines on when the formula will be rainproof, which could be anywhere between ten minutes to over two hours.

Either way, it’s a good idea not to apply a post-emergent herbicide if rain is forecast – just to be on the safe side.

Additionally, both pre and post-emergent weed killers need to be fully dry before they stand any chance of being pet and human friendly, so keep animals and children away until that happens.

Active Ingredients

It’s important to know and understand the active ingredient of a weed killer. This will basically inform you what is actually doing the killing – and how that killing will take place.

Different chemicals, compounds, and formulas will attack weed and plant life in different ways. Some might be root inhibitors, others might prevent the protection of chlorophyll, or affect cell membrane production.

Understand the active ingredient will also help you understand which plants the herbicide will or will not attack.

From a safety perspective, some active ingredients are more harmful to us humans than others – so care must be taken with their use.

FAQs

Close up of field plants

Is Roundup a post-emergent?

It depends on which Roundup product you’re talking about as their range is extensive and it can be a challenge to choose the right one.

While most Roundup products are post-emergent herbicides, the brand also manufactures some pre-emergent weed preventers, too.

Check to see when the product is applied for confirmation.

When should I apply post-emergent?

Again, it depends on the particular product.

Some post-emergent herbicides are best applied at a certain time of year, or in certain temperatures and soil conditions.

But they will nearly all be most effective when applied in early spring when the weed is young and growing.

Having said that, a post-emergent herbicide is designed to attack and kill weeds that have already grown and are established – so feel free to unleash the liquid death whenever you see weeds protruding from the soil.

What is the strongest post-emergent weed killer?

There are a few contenders for the crown of strongest post-emergent weed killer, but it’s really all speculative and can depend on where and what you’re treating.

Anything with a high concentration of the active ingredient is going to be pretty deadly – toxic or otherwise.

The Southern Ag, RM43, Roundup, Monterey, and Spectracide brands all have products that are extremely potent – but so do the lesser-known versions.

Head on over to this article on the best commercial weed killers if you’d like to know who the pros use, and then you can make your own mind up which is the strongest.

Sometimes, trial and error is the only way to know for sure.

Does post-emergent kill grass?

Green grass close up

It certainly will if it’s non-selective.

Selective post-emergent herbicides are available that only attack certain weeds, thus keeping your prized lawn intact while literally weeding out the invaders.

However, the vast majority of post-emergent weed killers are non-selective and are designed to simply destroy everything green that they touch.

Double-check your labels – and always dispense with great care, regardless of what category a particular herbicide falls under.

Can I apply pre-emergent and post-emergent at the same time?

You can – there’re no restrictions placed on the timing of application between a pre or post-emergent herbicide.

However, pre-emergents are most effective when laid in the early spring, fall, or early winter, whereas post-emergents thrive from late spring to mid-fall.

Not to mention the fact that you could well be trying to use a bunch of different chemicals that can treat some weeds but not others – which would prove a waste of time and money in the long run.

Certain products are useful as both pre and post-emergent herbicides, so when treating an area you not only kill existing weeds but it will remain clear of vegetation for a given period of time after application.

I would suggest trying them before attempting to concoct your own, crazy mix.

Furthermore, depending on the chemicals involved, there are likely application limits set by law, and mixing high concentrations of pre and post-emergent weed killers might be in breach of that – depending on your state’s regulations.

For more information, have a root around on the herbicides page of the United States Environmental Protection Agency.

In short, it’s best to err on the side of caution and only use one product at a time – and when it is recommended to do so.

Again, always refer to the labels – because they are literally the law.

What is the difference between pre-emergent and post-emergent?

A pre-emergent herbicide is designed to stop weeds from germinating. It is usually applied before the temperature of the soil reaches 55 degrees in spring, but it can also be used in the fall and early winter to prevent certain grasses or weeds from arriving the following year.

A post-emergent herbicide is for when the weeds have already broken through the soil, they’re visible, invasive, and growing. Post-emergent herbicides can be applied throughout the season to spot or blanket treat nuisance weeds and vegetation.

What herbicide will kill everything?

If you absolutely, positively, want to kill everything green, then choose a non-selective herbicide with a high concentration of its active ingredient.

This is most likely to be glyphosate – the world’s most popular weed killer.

It does not discriminate –  a high percentage of this stuff will pretty much destroy any plant life in your yard or garden.

However, it’s at your own risk. Glyphosate products have been on the receiving end of some seriously negative press over the past few years.

Summary

Herbicides are a controversial topic, but many gardeners the world over still swear by them for keeping their lawns and landscapes weed-free.

While prevention is better than cure (and good garden practices can help) the best post-emergent herbicides are often a necessary evil.

I would always choose the more organic, natural option if I had to use one – in this case, the Green Gobbler product.

But to each their own – let me know which product you would choose and why. Whatever you decide, always make sure to apply it safely, with care, and in accordance with the instructions.

Best of luck and happy weeding!