The 11 Best Pre-Emergent Weed Killers (The 2024 Edition) + Buyer’s Guide & FAQs

If there’s one thing that’s better than killing weeds in your garden – it’s preventing them from appearing in the first place.

That’s why botanical science boffins created products that do exactly that – and if applied correctly, can keep weeds at bay for up to a year.

Pre-emergent weed killers are designed to stop unwanted vegetation before it has a chance to germinate, so it’s possible that you won’t even see weeds rearing their ugly heads for the season.

Because prevention is much better than cure.

Read on to discover the best pre-emergent weed killers and find the one that’s right for you. A full buyer’s guide and FAQ section will follow.

Let’s nip those weeds in the bud.

The 11 Best Pre-Emergent Weed Killers in 2024

Scotts Halts Crabgrass & Grassy Weed Preventer

For the very best in lawn care, you can do a lot worse than Scotts, a household name when it comes to building turf like a putting green. This is their crabgrass and grassy weed preventer, a granular product that you apply over your lawn using a spreader.

It can be applied in the spring to prevent crabgrass and other problem weeds for the season, and it can also be applied in the fall to keep winter weeds at bay.

It’s not affected by weather after application, and a 10 lbs bag will treat an area of up to 5000 square feet. This is probably the best pre-emergent weed killer for Bermuda grass as it won’t harm it if you’re cultivating a Bermuda grass lawn.

Pros

Cons

Roundup Landscape Weed Preventer

Homedepot.com

As well as making some of the best post-emergent herbicides, the most recognizable weedkiller brand also manufactures a line of weed preventers. This also comes in granular form, but this time designed to be spread around annuals, established flower beds, and around trees and shrubs.

It creates a protective barrier in the soil, so you will be weed-free for up to six months, and you only need to apply it once per year before unwanted foliage has a chance to grow.

Simply apply using the easy-applicator, mulch, and then water to activate to prevent over 40 types of grassy and broadleaf weeds.

Pros

Cons

Preen Garden Weed Preventer

Homedepot.com

When it comes to pre-emergent weed killers, Preen products were never going to be far away – and now we have two in a row. First up is their standard weed preventer, a 16 lbs tub of granules that comes with a scoop spreader.

Distribute around bedding areas and then water to activate, and keep your garden weed-free for up to three months.

Safe to use in proximity to over 200 species of flowers, vegetables, trees, and shrubs, you’ll have peace of mind applying this even near your edibles. Best of all, it can be applied at any time throughout the season – just so long as you’ve cleared the area of existing weeds beforehand.

Pros

Cons

Preen Granular Garden Weed Preventer

Homedepot.com

This next Preen entry has all the benefits of the previous product, but this time with the addition of plant food.

As such, it’s the best pre-emergent weed killer for flower beds, as the balanced fertilizer is designed to promote blooms, increase yields for vegetables, and create strong and healthy root systems.

Again, perfectly safe for use around 200 established flowers, vegetables, trees, and shrubs, one application will feed your plants and prevent weeds for up to three months. The 16 lbs tub with applicator scoop covers 2,560 square feet, and it can be used throughout the season for effective results.

Pros

Cons

The Andersons Granular Pre-Emergent Weed Control

Made with .48% of the active ingredient prodiamine, this is a professional turf barricade from the Andersons that is designed to prevent summer annuals from appearing in your prized lawn. This includes crabgrass, goosegrass, and foxtail.

Most effective when applied in spring and prior to soil temperatures reaching 55 degrees, the DG pro formulation allows for more particles per square inch of the chemical, which significantly improves coverage and leads to better control of the weeds.

One of the best pre-emergent weed killers for lawns there is. This is a commercial-grade product for use around the home that won’t let you down.

Pros

Cons

Monterey LG 5130 Weed Impede Herbicide

Up next is Monterey’s Weed Impede herbicide, the first pre-emergent product in our review that comes in liquid form.

It’s a surface-applied herbicide used for the control of many annual kinds of grass and broadleaf weeds in ornamental plantings, rock gardens, bulbs, and ground covers.

Just one gallon can treat between 40 and 80 thousand square feet. Best applied with a pump-sprayer and mixed with the right amount of water, this will keep just about anything unwanted from sprouting up wherever it’s applied.

It also contains an orange dye so you can see exactly where you’ve treated – which is a bonus not to be underestimated, and highly useful for improving your accuracy.

Pros

Cons

Concern Weed Prevention Plus

Homedepot.com

Concern’s Weed Prevention Plus is an all-natural pre-emergent weed preventer that is safe for use around people and pets, so ideal if you have furry friends or little feet running around.

It prevents weeds while fertilizing your lawn, and one bag can cover up to 1,500 square feet.

Designed to be especially effective against crabgrass and dandelions (the banes of good lawn care), it also adds a lawn food for a healthy turf you can be proud of.

The active ingredient is natural corn gluten, meaning you can avoid those harsher chemicals with this product if you prefer.

Pros

Cons

RM43 Glyphosate Plus Weed Preventer

You might be wondering what RM43 is doing on this review of pre-emergent weed killers, and that’s because it works as a weed preventer as well as a spot treatment for existing growth. ANY growth – including murdering nettles.

After application, this will keep any area vegetation-free for up to one year, as well as destroying existing weeds in the process. As such, bear in mind it will kill anything green that it comes into contact with, so care should be taken around your desirable blooms.

Still, there’s not much out there that’s as potent or effective for keeping an area barren of plant life should you so choose. One gallon can treat up to 17,297 square feet, so you have a professional herbicide that is ideal if you need to control larger areas.

Pros

Cons

Tenacity Turf Herbicide

Like the RM43, Tenacity is a pre and post-emergent herbicide – which is why it’s justified its inclusion here. However, that is where the similarities end, as this is a selective herbicide that is safe for use on your turf lawns for getting rid of nuisance weeds only.

Very cost-effective, it’s used for residual control of undesirable plants in turf grasses, and will keep over 46 different broadleaf and grassy weeds away, with an active ingredient that is actually a naturally occurring compound.

Allow your new grass to flourish as Tenacity prevents invasive weeds from choking out your desirable lawn. And check out this article if you prefer to rid your lawn of weeds without harsh chemicals.

Pros

Cons

Quali-Pro Pre-Emergent Herbicide

This is a professional-grade, pre-emergent formula that contains a very high concentration of prodiamine at 65%.

Effective when used around nurseries, landscaping, turf lawns, and trees and shrubs, it’s this kind of product that the pros use when maintaining sports fields such as golf courses and putting greens.

It can be applied in both spring and fall for season-long control and inhibition of crabgrass and broadleaf weeds, and a little goes a very long way with this five-pound bottle.

Best used in a tank sprayer for covering larger areas, Quali-Pro have developed a genuinely effective pre-emergent herbicide with this formula.

Pros

Cons

Dimension 2EW Dithiopyr Pre-Emergent Herbicide

Our final entry in this review of the best pre-emergent herbicides is this Dimension 2EW product with the active ingredient dithiopyr – a root growth inhibitor.

This specialty, professional-grade herbicide provides pre-emergent and early post-emergent control of crabgrass, as well as 45 other nuisance weedy grasses and broadleafs.

In order to achieve post-emergent control, you should be looking at using two pints of the product per acre. Easily mixed in spray tanks, it’s also compatible with other specialty herbicides for maximum effectiveness and control of a wider range of weeds and is residual in the soil for around four months.

Pros

Cons

How to Choose the Best Pre-Emergent Weed Killer

In this next section, you’ll find further information and advice for choosing the right pre-emergent weed killer for you.

How Pre-Emergent Herbicides Work

Pre-emergent herbicides are most often used well before plant life has germinated – either in early spring or late fall.

They work by inhibiting a key enzyme that provides an invisible barrier through which seed growth cannot pass. Effectively, a pre-emergent herbicide neutralizes a plant before it has the chance to germinate.

Some products will also contain a fertilizer to feed desirable plants or an established turfgrass at the same time.

Any seedlings that have big ideas for seeing the light of day will be terminated by this invisible film in the soil, created when a pre-emergent herbicide has been applied correctly and watered to activate.

Quantity/Coverage

How much pre-emergent herbicide you need will obviously be determined by how much land you need to cover.

As mentioned, a pre-emergent herbicide is specifically designed for distribution over a wide area, so getting the coverage you need isn’t that challenging.

Again, just make sure you’re referring to the instructions when mixing liquid formulas – as achieving the right balance of water (and surfactant – if required) can often be the trickiest part of the process.

Liquid or Granules?

Pre-emergent herbicides are available in granular or liquid form. So it comes down to choosing one of these types of weed killers.

Granules are much easier to use and usually come with a scoop of some kind to assist with their application.

However, using a dedicated spreader is better if you have a larger area to cover – but they’re always sold separately. If you don’t have access to such a device, I would recommend picking one up second-hand to save a bit of cash.

While granular pre-emergent herbicides are usually cheaper than liquid versions, you’ll get much better coverage with a liquid.

And when it comes to the effectiveness of a pre-emergent – accurate and extensive distribution is key – which is where liquid herbicides excel.

Still, it can be a bit of a challenge to get mixing quantities right – especially if you’re using a surfactant (an additional liquid product that breaks surface tension and improves herbicide absorbency).

And liquids need the right kind of applicator to do the job, usually in the form of a tank or backpack sprayer. This I would recommend purchasing brand new – so you know that no other chemical has been used in it and you’re not risking any kind of cross-contamination.

Once both versions have been applied, you need to add water to activate. This is where liquid has another advantage, in that it will take less hosing or rainfall for the herbicide to begin working its magic in the soil.

Whichever version you choose, diligently read and understand the instructions before use.

Selectivity/Targeted Weeds

When choosing any kind of weed killer or preventer, you need to be aware of its selectivity.

Herbicides can be selective, or non-selective. Selective means that they will only treat certain types of plant life. Non-selective means they will attack anything.

When it comes to pre-emergent herbicides, it’s important to learn what the chemical is going to kill, and what it’s going to leave alone – if anything.

This is particularly true if you want to apply a herbicide to your lawn. You need to make sure it’s not going to harm existing, desirable plants and grasses.

This is where having an understanding of weed types is highly beneficial. Check out the video below for an excellent guide.

Advantages and Disadvantages of Pre-Emergent Herbicides

The Pros

Naturally, as with all such chemicals, a pre-emergent herbicide comes with its pros and cons. Let’s start with the good news.

Pre-emergents stop weeds in their tracks, meaning that with proper application and at the right time, you might not see a single weed in a treated area for the length of the season.

And speaking of time, a good pre-emergent will be effective for up to one year, and no less than three months – depending on quality.

Finally, the coverage square footage of a pre-emergent herbicide is a very attractive proposition for anyone with larger yards and gardens. Applying this solution is usually much easier and faster than a post-emergent weed killer.

Once again – prevention is much better than cure. For more information, have a look at this article on when to apply weed control.

The Cons

Now for the bad news. Post-emergent herbicides are useless on already established weeds and grasses – and you’d be surprised at just how many people get this wrong and complain when it has had no effect.

(There are one or two products that incorporate both types of herbicide, however, and will kill existing weeds and then keep the treated area plant-free. Still, standard pre-emergent weed killers do not kill visible weeds.)

Also, the timing and temperature of applying pre-emergent needs to be just-so – especially for the effective treatment of crabgrass.

If you’re too late or too early in spring or fall then you won’t have effective results. Whichever product you decide to try, make sure you adhere to the directions completely.

Last but certainly not least, pre-emergent weed killers are rarely pet-friendly. It’s highly advisable you keep children and animals inside – at least until the product has been watered into the soil, and has had a chance to dry.

FAQs

What month do you put down pre-emergent?

Always refer to a particular product’s directions (as they can vary from brand to brand) for the best month to apply the formula. By and large, you’ll want to be putting down a pre-emergent in the early spring or fall.

Certain pre-emergents can be applied throughout the season, but for the most part, the barrier should be down before weeds have a chance to grow – so get in early.

It will also depend on what weed you want to target, so again, make sure you know thy enemy before charging into battle.

Choosing the right product and using it at the right time is essential for your success.

What is the best time to apply a pre-emergent weed killer?

Again, it depends on the type of weed you’re looking to control, and the pre-emergent you’re using. Always read the label.

Check out the excellent video below for advice on using a pre-emergent in the spring – which is when most gardeners will be keen to block forthcoming weeds.

What is the best soil temperature for applying a pre-emergent weed killer?

For best results, you should be applying a pre-emergent herbicide BEFORE the soil has been at a temperature of 55 degrees or above for between 36 and 72 hours.

55 degrees is like DEFCON 1. When the soil temperature goes above that number for a sustained period of time, that’s when seeds begin to germinate, weeds start to become a problem, and then you’re at war.

You can use a soil thermometer, or you can contact your local county extension service for agricultural advice and soil readings in your area.

Alternatively, use this excellent soil temperature map and locate your area.

However, you’ll find that the soil will be around this temperature from March to April for the spring application of pre-emergents.

How long does pre-emergent last?

The residual effects of a pre-emergent herbicide will depend on the particular product you’re purchasing.

Generally speaking, you’ll find they last between 3-12 months. Check the label or specifications for further details before adding to the cart.

Can you put down too much pre-emergent?

Yes – and it can be a seriously grave error if you do with potentially disastrous results.

ALWAYS make sure you adhere to the guidelines on the product label – and like any drug or medicine you might take – never exceed the stated dose.

Also, be aware that the misuse of chemicals in and around your home and property can land you in serious trouble with the law. So, be sure to read that label thoroughly.

How soon can I seed after pre-emergent?

Depending on the pre-emergent (some products you won’t be able to seed at all) you should be waiting between 7-10 days before attempting any new work.

Can I put down pre-emergent and fertilizer at the same time?

Yes, and there are products that contain both – particularly in the Preen and Scotts ranges.

Just make sure you water them both down into the soil well.

Should you mow before pre-emergent?

You don’t have to, but it is recommended that your lawn isn’t a jungle when you apply a pre-emergent herbicide. You want the product to be watered into the soil, and that will be easier to accomplish if the grass isn’t too high.

Don’t mow your lawn for a few days after application though, so you can allow the stuff to take hold.

Will rain wash away pre-emergent?

No – in fact, quite the opposite.

Unlike a post-emergent weed killer, you want it to rain after you apply a pre-emergent, because it will save you from having to water the area you’ve treated, and activate the herbicide defense barrier in the soil.

Can you put pre-emergent on wet grass?

No. It won’t be as effective.

Apply the herbicide before it’s due to rain on dry grass and soil, and then water it yourself if no rain is forecast.

Should you water after using a pre-emergent?

Yes! That is how you allow the chemical to activate and get to work protecting your soil and preventing weeds from germinating.

It’s best to add around 1/4-inch of water to the treated area once you’ve applied the herbicide.

Does pre-emergent kill existing weeds?

It depends on the product. Certain pre-emergent weed preventers also incorporate post-emergent weed killers – so they’ll kill anything they come into contact with and keep that area totally plant free for the foreseeable future.

However, by and large, pre-emergent herbicides are useless for killing already established weeds – particularly if they’re already visible through the soil or concrete.

Check out this article for the best weed killers for driveways if you need a post-emergent product that will destroy unwanted plant life where it shouldn’t be growing in the first place.

Summary

The world of herbicides is a complex one, and finding the right product and figuring out the right time for application can be a real headache.

I hope this article and review has helped you choose the best pre-emergent weed killer for your garden project, and that you have much success in keeping weeds at bay as a result.

For my lawn, I would choose the Tenacity product, and possibly the Preen Weed Preventer with plant food for around desirable foliage in landscape beds.

Let me know which pre-emergent you would choose and why.

If you are dealing with more than just weeds, but there are also stumps to kill, take a look at the best stump killers that we recommend.

Happy weeding!