There are two ways to get rid of weeds: before they sprout and after they sprout.
If you wait until summer to start killing weed, you’ll have to endure weeks or months of slowly dying weeds making your lawn look ragged and patchy.
If you do it in late winter or early spring before the seeds germinate, sprout, and emerge from the soil, you won’t have to put up with any of that.
It takes some work and planning (well, maybe more than “some”), but the end result will be a yard you can brag about without having to worry about pulling weeds all the time.
In this review, you can expect to learn:
- What are pre-emergent weed killers?
- How do pre-emergent weed killers work?
- Are pre-emergent weed killers effective?
- How do you use a pre-emergent weed killer?
- And our overall #1 pick for best pre-emergent weed killer!
If you're short on time, you can click here to jump straight to our top choice for best pre-emergent weed killer.
| Image | Product | |||
|---|---|---|---|---|
Our Top Pick  | Our Top Pick | Southern Ag Surflan A.S.
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| View on Amazon |
 | Green Light Amaze Grass and Weed Preventer
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| View on Amazon | |
 | Bonide DuraTurf Crabgrass and Weed Preventer
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| View on Amazon | |
 | Hi-Yield Crabgrass And Weed Killer
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| View on Amazon |
Our Overall #1 Rated Pick
(updated as of 04/13/2020)
- The active ingredient is Oryzalin
- Controls weed seeds
- Four-month residual impact
This is a liquid pre-emergent herbicide in a 32-ounce bottle. You only have to use 1.5 ounces of concentrate per gallon of water to cover 1,000 square feet. It’s a little more expensive than some but the results are worth it.
It can be safely used on bahiagrass, bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass to kill annual grass weeds including crabgrass, annual bluegrass (poa annua), and goosegrass.
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Top 4 Best Pre-Emergent Weed Killers
What Are Pre-Emergent Weed Killers?
A pre-emergent herbicide is a weed killer that has to be sprayed or spread long enough before weeds begin sprouting that the herbicide has time to soak into the ground down to the depth of the seeds. It’s preemptive weed control, killing them before they sprout.
By contrast, post-emergent means after a plant has emerged from the soil, so a post-emergent herbicide is a weed killer that can only be used on broadleaf weeds, grassy weeds, and others after they emerge from the soil and produce their leaves.
For more information on what pre-emergent weed killers are, and when to use them, check out the video below!
How Do Pre-Emergent Weed Killers Work?
Pre emergent weed killers do not kill weeds before they begin germinating. Instead, they interfere with their growth to prevent them from completing the germinating process.
Pre-emergent herbicides can be classified as a growth regulator. If the weed can’t finish growing, it dies.
Are Pre-Emergent Weed Killers Effective?
Yes, if you follow the directions on the label. Herbicide labels contain important safety information for use, storage, and disposal. For your safety and the safety of those around you, you need to read that information and follow it exactly.
The first line on every label reads, “It is a violation of federal law to use this product in a manner inconsistent with its labeling.” This has given rise to the saying, the label is the law, which is literally the truth.
How To Use A Pre-Emergent Weed Killer
Pre-emergent herbicides can be liquids that require a low-pressure sprayer for their application, or granules that need to a hand spreader for broadcasting them across the lawn. Your lawn care herbicide application also requires the use of a soil temperature thermometer.
You need a soil thermometer because timing is critical when you’re using a pre-emergent herbicide. The soil has to be at the correct temperature before you apply the herbicide. The ideal soil temperature range is 50-55 degrees.
When your soil reaches that point will depend on what latitude you’re at. The further north you are, the later in the year it will be. At the extreme southern tip of Texas, it could as early as January 1. Above the 45th Parallel, it could be anytime after May 30.
Take daily soil temperature readings until the temperature is within that range for 2-3 days in a row. Once that happens, it’s time to begin your application.
Liquid Herbicides
Mix the herbicide with water according to the directions on the label. A 3-4 gallon backpack sprayer will be sufficient for treating most yards. You should only have to refill it a few times to treat the whole yard.
Begin spraying at the foundation of your house in a gradually increasing spiral around the house until you’ve covered the entire yard. Each band of the spray should overlap the previous band by several inches to ensure complete coverage.
Once you’ve finished the application, follow any directions on the label for agitating or tilling the soil. If you don’t or can’t till the soil, a second application may be necessary. See the label for details.
Granule Herbicides
Granules are easy to spread. Follow the directions on the label to set the spreader release the appropriate amount of granules. You should turn the handle about twice per second while moving at a normal walking pace, around 3mph.
Use the same gradually increasing spiral pattern as for a liquid herbicide. Once you’re finished, follow the directions on the label for how much to water your yard. Granules are almost always water activated so this is a necessary step.
Are Pre-Emergent Weed Killers Safe Around My Pets And Children?
No. Herbicides, pre-emergent or post-emergent, are toxic chemicals designed to kill plants. While people and plants are different, we still share many commonalities and herbicides can cause chemical injuries to people if precautions aren’t taken.
Warning
Pets and children should be kept out of treatment areas during the application process and for 24 hours afterward unless the instructions on the label list a different length of time.
Best Pre-Emergent Weed Killers Reviewed
- The active ingredient is Oryzalin
- Controls weed seeds
- Four-month residual impact
This is a liquid pre-emergent herbicide in a 32-ounce bottle. Use 1.5 ounces of concentrate per gallon of water to cover 1,000 square feet. Do not reseed for 90-120 days after the application or it will kill the grass seed.
It can safely be used on bahiagrass, bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass to kill annual grass weeds including crabgrass, annual bluegrass (poa annua), and goosegrass.
It is labeled for use on ornamentals, non-cropland, non-fruit bearing trees and vines, industrial sites, and established warm-season turf.
Pros
Cons
- The active ingredients are Oryzalin & Benefin
- Ready to use
- Four-month residual impact
This pre-emergent herbicide comes in a 10-pound bag of granules. One application will prevent weeds for up to four months. It controls annual bluegrass, chickweed, crabgrass, foxtail, goosegrass, henbit, prostate knotweed, and purslane, among others.
It can safely be used on established turfgrass such as bahiagrass, bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass, up to 4,000 square feet per bag.
It is also safe to use on established flowers, roses, shrubs, and trees. See the label for a complete list.
Pros
Cons
- The active ingredient is Dithiopyr
- Convenient shaker
- Long-term control
This pre-emergent herbicide comes in a 4-pound jug of granules. It prevents germination to give you long-term crabgrass control. It’s ready to use in a shaker so you don’t need a spreader.
It also kills annual bluegrass, barnyard grass, chickweed, crabgrass, dallisgrass, foxtail, goosegrass, henbit, knotweed, purslane, speedwell, and spurge. It’s safe to use on bahiagrass, bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass.
The small package lends itself to use on small yards and spot treatments rather than large yards or fields.
Pros
Cons
- The active ingredient is Dithiopyr
- 4,000 square feet per bag
- Good price point
This is a pre-emergent herbicide in a 12-pound bag of granules. The active ingredient is listed as Dimension, another name for Dithiopyr. This is a consumer-use product only, not intended for commercial use. One bag covers about 4,000 square feet.
It kills annual bluegrass, barnyard grass, chickweed, crabgrass, dallisgrass, foxtail, goosegrass, henbit, knotweed, purslane, speedwell, and spurge. It’s safe to use on bahiagrass, bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass.
Pros
Cons
Our Top Pick: Southern Ag Surflan A.S.
This liquid pre-emergent herbicide covers 1,000 square feet with only 1.5 ounces. It can be safely used on a wide array of turf while killing an equally wide range of weeds.
Surflan A.S. - Pre-Emergent Herbicide can be used on ornamentals and non-fruit bearing trees. On the expensive side, but completely worth it.
- The active ingredient is Oryzalin
- Controls weed seeds
- Four-month residual impact
Once a weed emerges, it can be a much harder job to clean up your lawn or garden. So grab a quart of Southern AG Surflan A.S. and solve the problem before it emerges!
Final Thoughts On Pre-Emergent Weed Killers
Pre-emergent herbicides are the best choice for long-term weed prevention. They create a preventative barrier that stops weeds before they get started. Using them requires a bit more elbow grease than with post-emergent herbicides but the results are worth the extra work.
Make sure the weeds in your yard are listed, then buy with confidence, knowing you can keep them off your lawn.
Other Weed Guides
Curious about other weed related products? Check out our other detailed guides to help you deal with your pest problems.
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