Consumer Mentor is reader-supported. We may earn commission on sales through our links at no extra cost to you.
Pre-emergent herbicides are chemical formulations applied to areas with problematic weeds. They are used before weeds emerge. The active ingredient in the herbicide inhibits the growth of sensitive root tissues in young or undeveloped plants. If applied at the right time and weather condition, it will kill the target weeds at the root level and give them no chance to sprout above the ground.
Before looking for the best pre-emergent herbicide for your yard, lawn, or farm, it is important to first learn about this type of weed control solution.
 |  |  |  |  | |
|---|---|---|---|---|---|
| Name | Snapshot 2.5 TG Granular Pre-Emergent Herbicide | Prodiamine 65 WDG Pre-Emergent Herbicide | The Andersons Pro Turf Barricade Granular Pre-Emergent Weed Control | Preen Extended Control Weed Preventer | Scotts Halts Crabgrass & Grassy Weed Preventer |
| Size, pounds | 50 | 5 | 50 | 4.93 | 10 |
| Application rate, pounds per 1000 square feet per year | 2.3-4.6 | 0.023-0.052 | 3.1-7.2 | 6.12-18.37 | 2 |
| Weed control effectiveness period, months | 6-8 | 2-3 | 2-3 | 6 | 3-4 |
| Active ingredient/s | Isoxaben, Trifluralin | Prodiamine | Prodiamine | Trifluralin, Isoxaben | Pendimethalin |
| Our review | Review | Review | Review | Review | Review |
| Where to buy |
Important things to know about pre emergent herbicides
1. Identify the weeds infesting your area and know their lifecycle.
Annuals—like crabgrass and cheatgrass—germinate from seed and produce seeds, completing this cycle in one year. Biennial weeds, on the other hand, complete this cycle in two years and germinate almost all year round. Perennials, such as dandelions and dallisgrass have thick adult roots that are capable of storing nutrients throughout winter and supporting new leaves and stems in spring. They can repeatedly go dormant and regrow over many seasons.
2. Pre-emergent herbicides are most effective in controlling annual weeds.
Pre-emergent herbicides do best at eliminating annual weeds. There are two sub-classifications of annuals. Those that germinate from spring through summer, such as crabgrass, are called summer annuals. Downy brome and shepherd’s purse germinate from fall through winter and are examples of winter annuals.
As for perennial and biennial weeds, they need to be controlled using other types of herbicide. Always read the label of a pre-emergent herbicide that you’re considering for your lawn. It will specify the weeds that it can control and the plants that tolerate it.
3. Timing is critical.
Apply in spring or fall. If applying in spring, do so when the air temperature ranges from 65°F to 70°F for four consecutive days. In autumn, use when the low temperature at night ranges from 55°F to 60°F for four straight nights. A second application may be required 6-8 weeks after the first application depending on the formulation of herbicide used.
4. Pre-emergent herbicides are not effective against established weeds.
They will only affect the immature root systems of germinated seeds and not those weeds with fully established roots. Take note that un-germinated seeds may stay dormant and unharmed by the herbicide. This means that they may later germinate when the herbicide has lost its potency. It is for this reason that herbicides should be applied regularly.
5. Pre-emergent herbicides can kill your plants, too.
To ensure that you don’t harm young plants, allow them at least six weeks to establish their roots first before you apply a pre-emergent for the weeds. If you have already treated the ground with a pre-emergent herbicide, wait for three months before planting new seeds.
Our Top 5 Best Pre-emergent Herbicides Picks – Reviewed
1. Snapshot 2.5 TG Granular Pre-Emergent Herbicide
- Size, pounds: 50
- Application rate, pounds per 1000 square feet per year: 2.3-4.6
- Weed control effectiveness period, months: 6-8
- Active ingredient/s: Isoxaben, Trifluralin
Target pests/weeds: 111 broadleaf and grassy weeds including aster, barnyard grass, crabgrass, fiddleneck, horseweed, junglerice, knotweed, lambsquarters, mallow, nightshade, ragweed, shepherd’s purse, and witchgrass
For use on: Landscape, field-grown and container ornamentals, perennials, ground covers, non-bearing fruit and nut trees, non-bearing vineyards, Christmas tree plantations, and non-cropland
Snapshot 2.5 TG granular pre-emergent herbicide is a selective weed control formula made for specific broadleaf weeds and annual grasses. The list of weeds that it can control is long and quite impressive. It comes with complete instructions on proper application, along with a list of plants that tolerate Snapshot well.
- Broad ranged – it targets 111 broadleaf and grassy weeds. Check the label of Snapshot 2.5 TG for the complete list of weeds that it can control.
- It holds up for a long period – it is effective for 6-8 months.
- Easy to use – application is quite simple. Use a rotary or drop-type spreader to apply the granules. You may also improvise with hand-held cans with small holes for small areas. You need to observe the indicated safety precautions, though, such as wearing gloves, long-sleeved shirt and long pants or coveralls, socks, and shoes.
- Can be stored after opening – it can be sealed in its original packaging, locked in a lidded container, and stored in a cool, dry place for use in the next 1 or 2 years.
- Safe for shrubs, bushes, and ornamentals – these plants are generally tolerant to Snapshot 2.5 TG as long as they are fully grown and established. The label lists in detail all the plants that are tolerant to it.
- Not for use in turfgrasses – it’s not labeled for lawns or turfgrasses.
- Not effective for perennial weeds – like most pre-emergent herbicides, it does not work for perennial weeds or weeds that grow from rhizomes, stolons, and root pieces.
- May need more than one application – you may need to apply a second time in areas with weeds that are aggressive or have a different germination time.
- Cannot be used on vegetable gardens – it is not safe to use on edible plants.
- Not safe for pets and children – it should not be used in areas frequented by pets, children, or farm animals. Pets may be allowed in the area only after the applied herbicide had been watered in and allowed to dry.
2. Prodiamine 65 WDG Pre-Emergent Herbicide
- Size, pounds: 5
- Application rate, pounds per 1000 square feet per year: 0.023-0.052
- Weed control effectiveness period, months: 2-3
- Active ingredient/s: Prodiamine
Target pests/weeds: 31 broadleaf and grassy weeds including annual bluegrass, crabgrass, foxtail, henbit, knotweed, and spurge
For use on: Lawns and turfgrass, sod nurseries, landscape ornamentals, field-grown ornamentals, container ornamentals, conifer and hardwood seedling nurseries, perennials, Christmas tree plantations, and non-cropland, like roadways and parking areas
Prodiamine 65 WDG (wettable dispersable granule) is a generic equivalent of Barricade. It is a wide-spectrum pre-emergent herbicide formulated for 31 broadleaf and grassy weeds. It can be mixed with compatible herbicides to improve the range of weeds controlled, including weeds that have already emerged.
- Can be used on lawns – Prodiamine is safe to use in established turfgrasses.
- Application rate is lower – it is more economical to use because of its lower application rate per 1,000 square feet per year.
- Safe to mix with other herbicides and fertilizers – it can be safely combined with compatible herbicides and fertilizers. Refer to the product label for compatibility test and mixing instructions.
- Safe for newly-transplanted container plants – it can be safely applied by broadcast or over-the-top to transplanted plants, as long as the soil has already settled around the plant. Water the plant thoroughly before application.
- Long shelf life – it has a shelf life of 3 years.
- Can be harmful to humans – always observe the necessary precautions when mixing or applying Prodiamine or other chemical-based solutions. Wear chemical-resistant gloves, long-sleeved sleeves, pants or coveralls, waterproof boots, face mask, and safety glasses. Do not allow entry into the treated area within 12 hours after application.
- Not for use on edible plants – do not spray in areas planted with crops and fruit-bearing trees meant for food use.
- Not safe to apply on putting greens – this herbicide can be used to control weeds in golf courses, but not on putting greens.
- Split applications might be necessary – stubborn weeds, like goosegrass, are typically eradicated with one dose of Prodiamine. In heavily infested areas, however, a divided application or two treatments per year might be necessary.
- Should not be applied with dry fertilizers – it can be safely used with liquid fertilizers but not with dry fertilizers. You may only apply dry fertilizer two weeks after treating the same area with Prodiamine.
- Not packed as pictured – it arrives, not in a plastic jug like the picture, but in a non-resealable mylar bag instead.
3. The Andersons Pro Turf Barricade Granular Pre-Emergent Weed Control
- Size, pounds: 50
- Application rate, pounds per 1000 square feet per year: 3.1-7.2
- Weed control effectiveness period, months: 2-3
- Active ingredient/s: Prodiamine
Target pests/weeds: 31 broadleaf and grassy weeds including barnyard grass, chickweed, crabgrass, henbit, itchgrass, junglerice, knotweed, lambsquarter, parsley, shepherd’s purse, and witchgrass
For use on: Landscape and field-grown ornamentals, perennials, turfs and lawns, golf courses excluding putting greens, parks, athletic fields, sod farms, Christmas tree farms, roadsides, and conifer and hardwood nurseries, other non-cropland
The Andersons Pro Turf granular pre-emergent herbicide contains the same active ingredient as Prodiamine 65 WDG. The difference is that this is applied dry and does not require mixing with water like Prodiamine 65 WDG. Application rate and instructions differ slightly, but they target the same weeds and have similar effects overall.
- Safe to use on turfs – it is safe to apply on turfgrass, lawns, athletic fields, and golf courses but excluding putting greens.
- Easy to apply – it does not need mixing like the generic Prodiamine which has to be added to water. The label lists some of its recommended spreaders. The important thing is to follow the recommended application rate and to water the area after application.
- Safe to most plants and trees – it will not harm established flowers, shrubs, vines, and trees.
- Will not harm seedlings – it is safe to use in conifer and hardwood nurseries as long as the soil has already settled around the seedling.
- Useful in managing transport and utility areas – it is one of the best pre-emergent herbicides to use for weed management in roadways, roadsides, railroads, parking areas, ungrazed fencerows, and equipment yards.
- Not for use on container plants – this herbicide is well tolerated by ornamentals, like magnolia, iris, and rose of Sharon, as long as they’re on the ground and not in containers.
- Not for use on food-producing plants – it works well for herbs and fruit trees that are not intended for food use or not yet at the fruit-bearing stage.
- A second application might be needed – some areas may require a higher rate or a second application for better weed control. The label recommends a second application for states in zones 4 and 5.
- May affect stressed plants – there are over 200 plants that are tolerant to The Andersons Pro Turf herbicide. Still, it can harm these species, especially those that have been damaged by heat, frost, or drought.
- Effectiveness is short-lived – it controls weeds for only 2-3 months. You may apply a higher rate for more extended coverage but not to exceed the maximum annual application rate.
4. Preen Extended Control Weed Preventer
- Size, pounds: 4.93
- Application rate, pounds per 1000 square feet per year: 6.12-18.37
- Weed control effectiveness period, months: 6
- Active ingredient/s: Trifluralin, Isoxaben
Target pests/weeds: 125 broadleaf and grassy weeds including aster, bittercress, crabgrass, fiddleneck, horseweed, junglerice, knotweed, lambsquarters, mallow, nightshade, ragweed, shepherd’s purse, and witchgrass
For use on: Xeriscape setting, rock gardens, perennials, ground covers, shrubs, and trees
Preen Extended Control Weed Preventer is similar to Snapshot 2.5 TG in many ways. It is also formulated with the same active ingredients but in a different composition. It comes in a smaller and handier package, which makes it ideal for smaller applications.
- Wide-spectrum herbicide – Preen controls more than 125 broadleaf and grassy weeds.
- Long control period – it provides 6-month protection, which makes it perfect for areas infested by different weeds with different life cycles.
- Safe to use for over 600 plant species – it is labeled safe to use for more than 600 perennials, groundcovers, shrubs, vines, and trees.
- Container with a flip-top lid doubles as spreader – it comes in a jug container with a lid that works as an applicator or spreader for small areas. This thoughtful feature makes it very easy to use.
- Guaranteed year-round protection – twice-per-year application ensures year-round weed protection.
- Cannot be used on turfs or lawns – this Preen herbicide is not safe for turfgrass.
- Not safe for food-producing gardens – it should not be applied in areas cultivated for food use, such as vegetable gardens.
- May cause staining – stray granules may stain concrete surfaces, stone paths, and other surfaces.
- May injure ground covers and other plants – Preen could harm plants that are not established at the time of application.
- Not ideal for fruit-bearing trees, shrubs, and vines – these plants tolerate Preen Extended Control very well. Their fruits, however, will not be safe to eat if harvested within one year of application.
- Not recommended for container plants – its concentrated formulation can damage shrubs, flowers, and vines planted in containers or pots.
5. Scotts Halts Crabgrass & Grassy Weed Preventer
- Size, pounds: 10
- Application rate, pounds per 1000 square feet per year: 2
- Weed control effectiveness period, months: 3-4
- Active ingredient/s: Pendimethalin
Target pests/weeds: 11 broadleaf and grassy weeds including crabgrass, foxtail, spurge, oxalis, poa annua, henbit, goosegrass, and chickweed
For use on: Lawns
Preen Extended Control Weed Preventer is similar to Snapshot 2.5 TG in many ways. It is also formulated with the same active ingredients but in a different composition. It comes in a smaller and handier package, which makes it ideal for smaller applications.
Maintaining lawns and turfs need not be tedious with a weed preventer made especially for lawn grass. One application will protect your turf from problem weeds all through the season. If applied in early spring, it will deter crabgrass, foxtail, spurge, barnyard grass, fall panicum, oxalis, and goosegrass all season long. If you repeat the treatment in early fall, it will prevent the emergence of moss, poa annua, henbit, chickweed, and corn speedwell.
- Ideal for most lawns – Scotts Halts pre-emergent herbicide is safe for almost all types of lawns and turfs.
- Easy to apply – spread over the area using a rotary or drop-type applicator. Make sure to calibrate the spreader for the correct rate, cover the area evenly, and water it in after application.
- Not affected by weather – once applied correctly, its performance will not be affected by rain, snow, or freezing temperature.
- Does not contain fertilizer – unlike the Scotts weed-and-feed product for turfs, this does not contain fertilizer. If you need just the pre-emergent herbicide and not the one with turf food, then this should be a better deal.
- Backed by a guarantee – Scotts extends a money-back guarantee if, for any reason, you’re not satisfied with the product.
- Not for use on dichondra and bentgrass lawns – it can potentially harm the germination of these grasses.
- Not available in 30 states – this herbicide is not available in AK, CA, CO, CT, DE, HI, ID, IL, IN, IA, KY, ME, MD, MA, MN, MT, NE, NV, NH, NJ, NY, ND, OH, OR, RI, SD, UT, WA, WV, WY.
- Can be harmful to humans and animals – it is necessary to wear proper clothing when handling this herbicide. Animals should only be allowed entry after the treated area has been watered in and dried. Don’t apply near waterways.
- Not safe for plants intended for food use – it should not be used on vegetable gardens and fruit or nut-bearing trees.
- Can cause staining – it can stain clothing, shoes, concrete, or stone. Brush off stray granules or wash stained materials immediately to reduce effects.
Conclusion
It’s easy to blame a product once your weed control strategy fails. To improve your chance of success, do your homework before trying to find the best pre-emergent herbicide for your garden or lawn. Know more about the weeds that you wish to eliminate. Identify them according to their life cycle, which describes how they grow and reproduce.
Use pre-emergents only for annuals that have not emerged yet, and strictly follow the manufacturer’s instructions on proper timing. Crabgrass, for example, germinates in spring, so the application must be in early spring. Annual bluegrass germinates in fall, so you should apply it in late summer or early fall. If you miss these windows, there’s no point wasting your time and money on a pre-emergent herbicide.
Weeds can still find a way to resurface, even after conscientious efforts on your part. Some seeds can lay dormant for long periods under the ground or can be blown by the wind from other areas to yours. For this reason, pre-emergent herbicides need to be applied periodically.
Leave a Reply