Stopping weeds early—before they can emerge from the soil—is the goal when applying a pre-emergent herbicide. A pre-emergent herbicide prevents the sprouting of undesirable weed seeds, so it’s a beneficial partner in the war against weeds in lawns, flower beds, and even vegetable gardens.
The best pre-emergent herbicide product will vary depending on the size of the area requiring treatment and the type of weeds the gardener wants to kill. This guide points out what to look for when shopping for a pre-emergent weed killer and lists several top products that can all help prevent these unwanted grasses.
- BEST OVERALL: Espoma Organic Weed Preventer
- BEST BANG FOR THE BUCK: Environmental Factor Turf Maize Liquid Fertilizer
- BEST FOR FLOWER BEDS: Gardener’s Supply Company Weedguard Plus Paper Mulch
- BEST WITH FERTILIZER: Sustane Spring Weed and Feed Corn Gluten
- BEST FOR LAWNS: Safer Brand Concern Weed Prevention Plus Corn Gluten
- BEST EASE OF USE: Lawnbright Organic Pre-Emergent Weed Control
Before You Buy Pre-Emergent Herbicide
Pre-emergent herbicides create a barrier that prevents weed seeds from sprouting. Because they stop roots from forming, pre-emergents are an effective way to control weeds, but they aren’t necessarily the right product for every weed in a lawn or yard.
A pre-emergent herbicide often prevents the germination of dandelions and crabgrass seeds, for example, but it won’t kill the plant once it’s established. When broadleaf weeds are mature, they’re tougher to get rid of, so a contact or systemic weed killer that attacks the leaves and root system may work best.
Some pre-emergent herbicides are fairly specific about the weeds they target. But others will kill almost any seed and aren’t a good choice for recently sowed flower borders, vegetable beds, or newly seeded lawns. Regarding ingredients, choosing sustainable, environmentally friendly options that won’t pose health risks or damage the soil is always the best bet.
How We Chose the Best Pre-Emergent Herbicides
We looked at the various types of pre-emergent herbicides on the market to determine our top picks, each of which is suited to specific shoppers looking for a particular characteristic for their yard.
While our research did find that there are two types of herbicides available—liquid and granules—we found that granules were more effective at providing long-lasting weed prevention. Many traditional liquid options are prone to overspraying and can burn the affected areas. Fortunately, most organic liquids are far kinder to both plants and people, so while compiling our list of recommendations, we were able to find a variety of different products.
As with any of the household or garden chemicals we investigate, sustainability is a key part of our selection process. It remains a challenge to find proven organic pre-emergent herbicides, though during our research, we discovered a variety of solutions that satisfy many organic principles.
Our Top Picks
The best pre-emergent herbicides are safe, sustainable, prevent a wide variety of weeds from sprouting, and offer easy-to-follow instructions. All of the following products will reduce hand weeding and help avoid the need for additional post-emergent treatment of weeds.
Espoma Organic has been creating organic garden products since 1929. Few brands have more experience in this market. Its granular pre-emergent herbicide is made from corn gluten, with natural nitrogen to help feed lawns and established plants.
It is applied twice a year in the same manner as synthetic pre-emergent herbicides, so those switching up to sustainable practices will find it easy to use. The 25-pound bag will typically cover 1,250 square feet but can cover 2,500 square feet if it’s simply used as lawn feed. It should not be applied on newly seeded or overseeded lawns but is fine for established vegetable plants, flowers, and shrubs.
We have seen a small number of reports of the product giving off an unpleasant smell and attracting flies when damp, but this may be caused by incorrect storage or application.
- Type: Granules
- Quantity: 25 pounds
- Coverage: 1,250 square feet
- Completely safe for children and pets
- Prevents an extensive range of weeds
- Can be used on vegetable plots and established bedding
- Unpleasant smell when damp
- May attract flies
Get the Espoma Organic pre-emergent herbicide at Ace Hardware or True Value.
This pre-emergent herbicide from Environmental Factor comes as a concentrate to be mixed three parts water to one part liquid. This makes it very economical, with one bottle capable of covering up to 10,000 square feet.
Like most organic products, this one has been derived from corn gluten. The natural proteins have been bioengineered using water-based hydrolysate technology developed by Iowa State University. The result is a sustainable product that can be used as both an herbicide and fertilizer.
Turf Maize should be applied three times per year and should not be applied to recently seeded areas. A few users report clogging when paired with sprayers, which was caused by undissolved residue. Some also felt it wasn’t as effective as they had hoped. The container warns that it should be kept out of reach of children.
- Type: Liquid concentrate
- Quantity: 2.64 gallons
- Coverage: 10,000 square feet
- More economical than most granular alternatives
- Bioengineered for improved performance
- Made in the U.S. from American corn
- Not child- and pet-safe
- Can block spray nozzles
Get the Environmental Factor pre-emergent herbicide on Amazon.
The approach adopted by the Gardener’s Supply Company is not to use an herbicide at all, but to use a paper sheet made from natural wood pulp. This doesn’t actually stop germination but prevents light from getting to weeds, effectively smothering growth.
Weedguard Plus can be laid over unplanted areas and around existing plants. It’s easy to cut or pierce so new plants can be inserted through it. It makes it an ideal solution when creating flower borders or vegetable plots using seedlings. The paper reduces evaporation, keeping the soil moist for longer and reducing the need to water.
A major upside of using paper mulch is that it degrades during the growing season, adding useful fiber and nutrients to the soil. The downside is that when the new season rolls around, the paper has to be relaid or another herbicide needs to be used.
- Type: Paper mulch
- Quantity: Roll, 50 feet long by 3 feet wide
- Coverage: 150 square feet
- Made from certified organic wood pulp
- Retains moisture, thus conserving water
- Decomposes to feed the soil
- Only lasts 1 season
Get the Gardener’s Supply Company pre-emergent herbicide at Target or Gardener’s Supply Company.
Sustane Spring Weed and Feed is a corn gluten-based pre-emergent herbicide and fertilizer certified as organic by the Organic Materials Review Institute (OMRI). While it will provide some general protection, it specifically targets those broadleaf weeds that are particularly difficult to deal with once established.
Like many natural herbicides, Sustane contains a small amount of nitrogen—9 percent in slow-release format. This is excellent as a lawn food and for border planting. When used as a lawn fertilizer, a 30-pound bag will cover 5,000 square feet. But for weed control, the same bag only covers 1,500 square feet. Used as a pre-emergent herbicide, Sustane only needs to be applied once a year and is safe for children and pets.
- Type: Granules
- Quantity: 30 pounds
- Coverage: 1,500 square feet (weed control); 5,000 square feet (lawn fertilizer)
- Contains slow-release nitrogen for plant growth
- OMRI certified for sustainability
- Safe for children, pets, wildlife, and fish
- Quite pricey
- Provides less coverage than similar products
Get the Sustane pre-emergent herbicide on Arbico Organics.
Nitrogen is a component of corn gluten, so many organic pre-emergent herbicides include it as an ingredient. Concern Weed Prevention Plus goes a step further, adding phosphate and potash to encourage strong root development and overall plant health. This is beneficial to flowers and vegetables, and it’s particularly good for lawns.
Compared to other pre-emergents, Concern Weed Prevention Plus is competitively priced. However, while the fertilizer element works well, some buyers feel its weed control isn’t as good as it should be. Some have also found that the granules attract rodents, though this problem doesn’t appear to be widespread.
Although the product is deemed safe for children and animals, the phosphate content may be an issue. Eight states restrict use of fertilizers, and Minnesota, Oregon, and Virginia have banned them completely because this pre-emergent herbicide can potentially cause excessive algae growth in waterways, reducing oxygen for fish and other aquatic life.
- Type: Granules
- Quantity: 25 pounds
- Coverage: 1,500 square feet
- Formulated for better lawn growth
- Contains nitrogen, phosphate, and potash
- Competitive price
- Potential phosphate problems
- May attract rodents
Get the Safer Brand pre-emergent herbicide at The Home Depot.
Most pre-emergent herbicides either come as granules, which are best applied with a spreader, or as liquids that need to be diluted and applied with a sprayer. This often involves an extra expense to buy the necessary equipment. With Lawnbright, all that’s required is a garden hose, which simply connects to the included spray attachment.
Lawnbright weed control comes ready to use and is available in a range of bottle sizes to suit the lawn being treated. It’s made from corn gluten, and in addition to being nontoxic, it also complies with the USDA National Organic Program. However, despite claiming to be safer than “traditional” pre-emergent herbicides, Lawnbright’s product label warns that it should be kept out of the reach of children and that it can irritate skin and eyes.
- Type: Liquid
- Quantity: Small, medium, or large
- Coverage: Square feet: 3,000 (small); 5,500 (medium); 9,000 (large)
- Ready-for-use spray bottle
- USDA National Organic Program compliant
- Part of a complete lawn-care package
- Not child- and pet-safe
- Premium price
Get the Lawnbright pre-emergent herbicide on Lawnbright.
DIY Pre-Emergent Herbicide
Corn gluten meal is found in many commercially available organic herbicides, but it’s also possible to buy it from garden nurseries and farm feed stores or online. Applying corn gluten meal is done much like a granular pre-emergent herbicide. Simply sprinkle it over the lawn at a rate of around 20 pounds per 1,000 square feet and water it in.
Cornmeal (the difference in the name is small but important) can also be used, but this option isn’t as effective. Where corn gluten meal can be applied in early spring and fall, cornmeal should also be applied during the midsummer months.
A 50 percent saltwater solution is sometimes suggested as a natural pre-emergent and can prove effective if applied regularly. However, nothing else will grow in soil treated with it. That’s why this natural pre-emergent is more appropriate for paths and driveways. It should always be sprayed judiciously (never oversprayed) to avoid endangering flowers and other desirable plants.
An established market leader, the Espoma pre-emergent herbicide is popular and effective. The Environmental Factor pre-emergent herbicide is budget-friendly, but results may be inconsistent. Popular lawn and garden options like Quali-Pro Prodiamine, Preen Weed Preventer, and Scotts Turf Builder weren’t listed because they didn’t meet our sustainability guidelines—each contain harmful synthetic ingredients.
What to Consider When Choosing the Best Pre-Emergent Herbicide
Shoppers will want to be careful about choosing a pre-emergent herbicide. Some shouldn’t be applied on soil where seeds will be planted to start a flower or vegetable garden, for example, or on a lawn that’s seeded.
Also, pre-emergents vary in form, strength, and in the type of ingredients they contain. We prefer organic varieties, but acknowledge that many popular commercial herbicides contain toxins. There are risks involved in using synthetic products. Many commercial pre-emergents are labeled “weed preventers,” but that doesn’t mean they’re less damaging than “herbicides” or “weed killers.” Shoppers should always read label instructions for safe use and disposal.
Pre-emergent herbicides are available in two primary forms: liquid and granules. While they both prevent weeds from emerging, groundskeepers and gardeners may prefer applying one form over another. Either type will help reduce the need for manual weeding.
- Liquid: Available as either concentrated or full-strength for use in a pump-type sprayer, liquid pre-emergent herbicides are easy to apply and are well suited for treating lawns to protect them from invasive grasses and other weeds. Concentrated liquids are the form of choice for many commercial applications, such as on golf courses and in parks.
- Granules: Granular pre-emergent herbicides resemble tiny grains and can be applied by a drop spreader, a broadcast spreader, or simply shaken out of a cup onto the soil to control weeds. The granules dissolve and seep into the soil after watering to form a weed-germination barrier.
Rather than targeting different types of plants the way many post-emergent herbicides do, pre-emergents target plants in different stages of growth. A pre-emergent will stop a seed from developing roots or a shoot, but it will not harm a larger plant’s roots. Also, a pre-emergent herbicide will not kill the roots of perennial weeds, such as bindweed or witchweed, that may lie beneath the soil. This can be a source of confusion for gardeners who see weeds emerging after the application of a pre-emergent herbicide. To eliminate perennial weeds, it’s best to wait until they emerge from the soil and then treat them directly with a post-emergent herbicide.
Pre-emergent herbicides are broadly defined as either organic or synthetic.
- Organic: Almost all organic pre-emergent herbicides are corn-based. As an active ingredient, corn is effective against a variety of grassy weeds and also feeds the soil. Vinegar is an alternative but may have an unpleasant smell. Citric acid also works but is most beneficial for those who grow fruit trees.
- Synthetic: Active ingredients in synthetic pre-emergent herbicides include Benefin, Dithiopyr, Isoxaben, Prodiamine, Siduron, and Trifluralin among other toxic, harmful chemicals. These products may be selective herbicides that target a particular group of weeds or have a more general approach.
Increasing demand for more sustainable, environmentally friendly products has led many shoppers to seek safer, organic options. Our selection features products that follow guidelines set by the USDA’s National Organic Program and OMRI.
Pre-emergent herbicides form a barrier in the soil that stops weed seed germination. The average pre-emergent will usually protect an area for 1 to 3 months, but some can protect a lawn or garden even longer than that. Many manufacturers recommend applying pre-emergent herbicide products in the spring at about the time forsythia blooms are beginning to fade and then applying once more in early fall to prevent blown-in weed seeds from germinating. While the use of a pre-emergent may not stop all weeds from germinating, it will eliminate the majority of them, even if used only once a year.
Safety and Application
Whether it’s synthetic or organic, applying a pre-emergent when children and pets are not around is the most important safety rule. Here are a few more.
- Read the label. Herbicides sold in the U.S. usually carry a warning label against improper use, which can harm humans, wildlife, and the environment.
- Protect the body. Users should wear gloves, long sleeves, long pants, a dust mask, and eye protection during application to avoid direct contact.
- Apply on a calm day. Wind can carry herbicide spray, inadvertently contaminating an area intended for planting.
- Water after application. Watering encourages pre-emergents to seep into soil and form a barrier against seed germination.
- Wash afterward. Users should thoroughly wash and change clothes after application.
- Never pour unused synthetic herbicides down the drain or lavatory. This risks introducing toxins into the water supply. The local waste authority can offer disposal advice, particularly concerning concentrates.
Reducing the number of weeds in a garden or flower bed is the goal of many gardeners, and applying a pre-emergent herbicide can help. Our informative guide aims to address many issues and concerns shoppers usually have about buying and applying a pre-emergent, but sometimes additional questions remain. Here are answers to some of the most common ones.
Q. Will pre-emergent herbicide kill crabgrass?
No, a pre-emergent herbicide won’t kill established crabgrass, but it will stop the germination of new crabgrass seeds. Our article on how to get rid of crabgrass offers further advice.
Q. When should I apply pre-emergent herbicide?
For the best results, most pre-emergent herbicides should be applied at least once in the early spring and once in the fall. Check the product label for additional instructions.
Q. What is the best temperature to apply pre-emergent herbicide?
Apply a pre-emergent herbicide in the spring when outdoor temperatures are still relatively cool—around the low 50s—before weed seeds begin to germinate.
Q. Will rain wash away my pre-emergent herbicide?
Rain will actually help the pre-emergent herbicide seep into the soil to form a barrier against weed seeds. Only torrential rain would likely wash away the product.
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