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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: Preen Natural Vegetable Garden Weed Preventer
- 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 Weed Prevention Plus Corn Gluten
- BEST EASE OF USE: Lawnbright Organic Pre-Emergent Weed Control
Photo: amazon.com
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, including broadleaf andgrassy weeds.
A pre-emergent herbicide will prevent weed seedsfrom germinating dandelions and crabgrass, 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 that prevent weeds.
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.
Best Overall
Photo: acehardware.com
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 forweed control 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.
Product Specs
- Type: Granules
- Quantity: 25 pounds
- Coverage: 1,250 to 2,500 square feet
Pros
- Completely organic formula; safe for use around children and pets
- Prevents an extensive range of weeds from germinating in gardens and on lawns
- Can be used on vegetable plots and established beddings for added user-friendliness
Cons
- May emit an unpleasant smell when damp; may attract flies
Get the Espoma pre-emergent herbicide at Ace Hardware orTrue Value.
Best Bang for the Buck
Photo: homedepot.com
Like all Preen weed preventers, this pre-emergent product stops weed seeds from sprouting, but this one is entirely natural. It contains only corn gluten, which is known for preventing seed germination. This Preen product can be used in flower beds and around other types of plants—including fruits and vegetables.
Preen weed preventer is a natural product that comes in granular form and is easy to apply with the built-in shaker lid for fuss-free, uniform application. A single application will keep weed seeds from sprouting for 4 to 6 weeks. It can be used on bare soil or in conjunction with mulch, such as shredded bark or pea gravel. It should only be used where plants are already established. Seeds of desirable plants will not sprout if sown in soil that’s been treated with corn gluten until the granules biodegrade to the extent that they no longer act as a barrier to seed germination.
Product Specs
- Type: Pre-emergent corn gluten
- Quantity: 5 pounds
- Coverage: 250 square feet
Pros
- Prevents weeds while still feeding plants; perfect for flower beds and fruits and vegetables
- Easy-to-apply shaker lid built for added convenience and user-friendliness
- Long-lasting formula lasts for up to 3 months after application
Cons
- Won’t kill any existing weeds; may not be suitable for some users’ preferences
- Stops all seeds from sprouting, not just weed seeds; may harm desirable plant varieties
Get the Preen pre-emergent herbicide at The Home Depot, Ace Hardware, Tractor Supply Co., or Blain’s Farm & Fleet.
Best for Flower Beds
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The approach adopted by the Gardener’s Supply Company is not to use a 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 gardens or 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.
Product Specs
- Type: Paper mulch
- Quantity: Roll, 50 feet long by 3 feet wide
- Coverage: 150 square feet
Pros
- Made from certified organic wood pulp; safe for use around children and pets
- Retains moisture, thus conserving water for desirable plants to thrive on
- Highly biodegradable construction; decomposes over time to feed the soil
Cons
- Only lasts 1 season; needs to be purchased every year
Get the Gardener’s Supply Company pre-emergent herbicide at Gardener’s Supply Company.
Best with Fertilizer
Photo: arbico-organics.com
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.
Product Specs
- Type: Granules
- Quantity: 30 pounds
- Coverage: 1,500 square feet (weed control); 5,000 square feet (lawn fertilizer)
Pros
- Contains slow-release nitrogen for plant growth; targets pesky broadleaf weeds
- OMRI certified for sustainability and reliability; safe for eco-conscious users
- Formula is safe for use around children, pets, wildlife, and fish
Cons
- Provides less coverage than similar products; multiple units may need to be purchased
Get the Sustane pre-emergent herbicide at Arbico Organics.
Best for Lawns
Photo: homedepot.com
Nitrogen is a component of corn gluten, so many organic pre-emergent herbicides include it as an ingredient. Safer Brand 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, Safer Brand 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.
Product Specs
- Type: Granules
- Quantity: 5 pounds
- Coverage: 250 square feet
Pros
- Formulated for better lawn growth as well as weed prevention
- Powerful anti-weed formula; contains potent nitrogen, phosphate, and potash
- Ample quantity provided for application on flowers, vegetables, and lawns
Cons
- Potential phosphate problems can be bad for wildlife in surrounding areas
- May attract rodents; caution advised when applying, and additional pesticide may be required
Get the Safer Brand pre-emergent herbicide at Safer Brand.
Best Ease of Use
Photo: getlawnbright.com
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 liquid pre-emergent herbicide, 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. One bottle covers up to 1,500 square feet. It is made from corn gluten, and in addition to being nontoxic, it also complies with the USDA National Organic Program.
Product Specs
- Type: Liquid
- Quantity: Small, medium, or large
- Coverage: Square feet: 2,500 (small); up to 5,000 (medium); over 5,000 (large)
Pros
- Ready-for-use spray bottle; easy for targeted or general application
- USDA National Organic Program–compliant product provides reliability and trust
- Comes in many different sizes/quantities to accommodate garden or yard sizes
Cons
- Lawnbright should be reapplied every 2 months during the growing season
Get the Lawnbright pre-emergent herbicide at Lawnbright.
Or, DIY Your Own 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 at controlling weeds 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.
Our Verdict
An established market leader, the Espoma pre-emergent herbicide is our choice for the best pre-emergent herbicide. 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.
Jump to Our Top Picks
What to Consider When Choosing a 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, effective pre-emergent herbicide options 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 will want to take care to always read label instructions for safe use and disposal.
Form
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.
Selectivity
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.
Ingredients
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.
Longevity
Most users apply pre-emergentherbicides to form a barrier in the soil and stop 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, as they 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.
FAQs
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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