Pre-emergent weed killers make lawn and garden care a little easier by preventing undesired weeds before they appear.
They work by creating a protective barrier in the soil, and this barrier does not allow plants to grow beyond germination.
If a weed seed germinates and begins to sprout, the plant will die when it reaches the layer of herbicide in the soil.
Most pre-emergent herbicides are non-selective, which means they do not differentiate between weed and grass seeds.
For this reason, you do not want to use a pre-emergent herbicide after sowing new grass seeds.
If you choose a selective pre-emergent herbicide, it is important to understand what the herbicide will and will not kill.
With this in mind, there are many options for different situations, so let’s talk about our 10 favorites (with some helpful content at the end).
Table of Contents
Quali-Pro Prodiamine 65 WDG Pre-Emergent Herbicide
Quali-Pro Prodiamine targets stubborn crabgrass as well as broadleaf weeds.
This herbicide is a concentrated granular product, which is diluted and applied with a pump-type sprayer.
In addition to crabgrass, this pre-emergent effectively kills annual Bluegrass, henbit, knotweed, chickweed, spurge, foxtail, and goosegrass.
The herbicide also mixes well with fertilizers and iron lawn supplements.
The active ingredient in this pre-emergent herbicide is 65% Prodiamine.
Pros:
- It kills stubborn crabgrass.
- It mixes well with iron and fertilizers.
Cons:
- It is expensive.
- It will stain your clothing.
Miracle-Gro Garden Weed Preventer
Miracle-Gro Garden Weed Preventer is a budget-friendly pre-emergent herbicide safe for use around roses, trees, shrubs, vegetables, and ground cover.
It is not recommended to use this herbicide near your lawn, however.
This is a granular herbicide, and it is effortless to use by sprinkling on areas needing treatment.
A five-pound container will treat up to 800’ square feet of garden space.
One application will last for up to three months, and it is most effective when applied in the early spring.
Pros:
- Inexpensive.
- Easy to use.
- Works for up to three months.
Cons:
- Does not kill crabgrass.
- The application method is not precise.
Preen Garden Weed Preventer + Plant Food
Preen Garden Weed Preventer + Plant Food is safe to use on flower beds, trees, shrubs, and ground cover.
This granular pre-emergent herbicide may be applied any time of year, and one application lasts for three months.
Not only does this product kill a variety of weeds, but it also provides nutrients for plants as well.
The main active ingredient in this herbicide is trifluralin, and it is a granular formula.
One 5.625 pound container will cover up to 900’ square feet.
Pros:
- Prevents weeds while nourishing other plants.
- Easy to use.
- Kills crabgrass.
Cons:
- Not meant to be used on lawns.
Preen Weed Preventer Plus Ant, Flea, & Tick Control
Preen Weed Preventer Plus Ant, Flea, & Tick Control is an herbicide with an added pesticide to help control ants, fleas, and ticks.
This pre-emergent herbicide is safe for flowering and ornamental plants, but not lawns.
It is a granular formula, and it may be used at any time during the growing season.
The active ingredient is dithiopyr, and it prevents the growth of weeds for up to four months after application.
A 4.25-pound container will cover up to 1,000’ square feet.
After distributing the granules, the area will need to be thoroughly watered.
Pros:
- Kills both weeds and pests.
- Easy application.
- The product is inexpensive.
Cons:
- Not meant to be used on lawns.
- The application method is not precise.
Scotts Turf Builder Halts Crabgrass Preventer with Lawn Food
Scotts Turfbuilder Halts Crabgrass Preventer with Lawn Food is another dual-purpose pre-emergent, which prevents weeds and nourishes plants.
This is an excellent pre-emergent herbicide to use on your lawn because it prevents crabgrass but encourages your grass to form a healthy and strong root system.
Poor weather conditions such as rain, snow, or freezing temperatures will not affect the performance of this product.
This herbicide is not meant to be used on dichondra or bentgrass lawns.
For optimal results, your lawn will need 1/4 to 1/2″ inch of water through rain or watering within three days of application.
Apply this herbicide in early spring for it to work all season long.
This product contains phosphorus, which poses a potential hazard to water quality through runoff.
Some states, such as Florida, have restrictions on phosphorus-containing products when used on non-agricultural lawns or turf.
Be sure to research your local laws so you will know if this herbicide is allowed to be used in your area.
Pros:
- Prevents crabgrass.
- Encourages a strong root system in plants.
- Easy to use.
Cons:
- Usage of this product is restricted in some areas.
- The product may clump up in the container, causing uneven application.
Preen Natural Vegetable Garden Weed Preventer
Preen Natural Vegetable Garden Weed Preventer is a natural pre-emergent herbicide with corn gluten as its main active ingredient.
Corn gluten forms a natural barrier to prevent weeds without using any chemicals, and it is safe for the environment.
This herbicide prevents broadleaf and invasive grasses such as crabgrass, clover, and dandelions.
The eco-friendly product is in a granular form, and it may be reapplied every 4-6 weeks.
A 5-pound container of this herbicide will cover up to 250’ square feet.
This pre-emergent herbicide is safe to use around vegetables, herbs, fruits, annuals, and perennials.
Pros:
- Safe for the environment.
- Prevents crabgrass.
- Easy to use.
Cons:
- Expensive for the small amount of product.
Barricade
Barricade is one of the longest-lasting pre-emergent herbicides on the market, with the ability to prevent weeds for up to six months with a single application.
This herbicide prevents 30 different types of annual grasses, perennial grasses, and broadleaf weeds, including poa annua and crabgrass.
The main active ingredient of this pre-emergent herbicide is 0.48% Prodiamine.
This product is a granular formula and is best applied in early spring or fall.
If you have recently seeded your lawn, you will need to wait 60 days or after the second mowing before applying the herbicide.
Pros:
- Stays active in the soil for up to six months.
- Easy to apply.
- Prevents crabgrass.
Cons:
- May burn your grass if applied incorrectly.
Tenacity
Tenacity is both a pre-emergent and post-emergent herbicide with 40% Mesotrione as the main active ingredient.
This herbicide prevents a variety of grassy and broadleaf weeds, including crabgrass, clover, chickweed, and dandelions.
Since this is a selective herbicide, it works to prevent weeds without causing harm to grass seeds.
The herbicide will stay in the soil for up to 30 days.
Because this is a liquid herbicide, you will need to use a commercial surfactant or dish soap to get the product to stick to weed leaves.
Pros:
- Safe for use on your lawn.
- Keeps working for up to 30 days.
- Easy to use.
Cons:
- The product is expensive.
- You may need multiple applications for the product to be more effective.
- This herbicide is slow-acting.
Pendulum 2G
Pendulum 2G works exceptionally well in preventing 40 different types of broadleaf and grassy weeds like crabgrass, poa annua, dandelion, and chickweed.
This herbicide is safe to use near annuals, perennials, and woody ornamentals.
One 40-pound bag of this herbicide will treat between 8,000-16,000’ square feet of garden area.
The active ingredient in this pre-emergent herbicide is pendimethalin.
This herbicide is toxic to fish and other aquatic wildlife, so avoid using it near any streams, ponds, lakes, rivers, or other bodies of water.
Pros:
- Prevents 40 different types of weeds.
- Easy to use.
- There is enough product in the package to treat a large area.
Cons:
- The bag is large and heavy.
- Toxic to fish and other aquatic wildlife.
Dimension 2EW Dithiopyr Pre-Emergent Herbicide
Dimension 2EW Dithiopyr Pre-Emergent Herbicide prevents and controls a variety of grassy and broadleaf weeds, including crabgrass and poa annua.
This is a liquid herbicide, and the main active ingredient is dithiopyr.
There are restrictions on using this product in the state of New York, where it is only allowed to be used commercially.
This product works best when it is applied in the early spring or fall.
Pros:
- Easy to use.
- Prevents a wide variety of grassy and broadleaf weeds.
Cons:
- Use is restricted in the state of New York.
When To Apply A Pre-Emergent Herbicide
Proper timing is essential when it comes to using a pre-emergence herbicide.
The soil needs to be warm enough for the seeds to germinate, so the weeds will die when the sprouts reach the barrier of herbicide in the soil.
The optimal soil temperature for applying a pre-emergent ranges between 50-55° degrees Fahrenheit (13° C).
Depending on where you live, your soil will reach this temperature in early or late spring.
You will find local soil temperature readings online, or you may buy your own soil temperature gauge to measure it yourself.
A few weeds germinate in the winter, such as chickweed, filaree, and poa annua.
If you have these weeds in your yard, you will need to apply a pre-emergent herbicide any time between early fall and early winter, depending on your climate.
Applying a pre-emergent herbicide in the summer is not advisable, as the soil may be too dry for the product to be effective.
How To Choose A Pre-Emergent Herbicide
There are a few things to consider when choosing a pre-emergent herbicide for your lawn or garden.
First, you will need to decide if you want a selective or non-selective herbicide.
Selective herbicides only kill specific types of weeds, so if you are concerned about your grass, you may want to choose this type.
It is also important to identify the weeds in your yard so you will be able to purchase the correct herbicide.
It is helpful to know if you are dealing with annual weeds or perennial weeds.
Always read the label on the herbicide so you will know which weeds it will kill.
If you have a newly seeded lawn, it is best to wait for a few months before applying a pre-emergent product in order to avoid any damage to your new lawn.
You will also need to research the ingredients in the herbicide you wish to use to ensure it is compatible with your grass.
Sensitive grass types, such as St. Augustine, are easily damaged by products containing dicamba or methylated seed oil.
There are granular and liquid pre-emergent products on the market.
Both formula types work well, so choosing one depends on personal preference.
The granular formula is usually applied with a drop spreader, while the liquid formula is used with a pump-type sprayer.
For more information, check out our article on when to apply weed and feed.
Commonly Asked Questions
Can you apply pre-emergent and weed & feed at the same time?
As long as the chemical formulas are compatible, a pre-emergent herbicide and a weed and feed product may be applied simultaneously.
If both products are granular formulas, they will work well together because they both need to be watered in around 2-3 days after application.
There are a few pre-emergent herbicides on the market which already include fertilizer in the formula.
Do I spray weed killer before or after mowing?
It is best to leave your lawn uncut for up to five days before and two days after applying weed killer.
Not mowing your lawn means there is more surface area on the weeds for the weed killer to cling to.
If the weeds are too short, the herbicide may be ineffective.
Do you water grass after pre-emergent?
It depends on the instructions on the product label, but in general, you do not need to water in granular pre-emergent herbicides.
The application area needs between 1/4 to 1/2″ inch of water within 2-3 days after the herbicide is applied.
If the treated area is watered or rained on too soon after application, the granules may be washed away, rendering them ineffective.
What is the most effective pre-emergent?
The three most effective pre-emergent herbicides are Prodiamine, Isoxaben, and Oxadiazon.
Prodiamine is the longest-lasting herbicide, and it has low application rates, making it more economical.
Isoxaben is the best at preventing a variety of broadleaf weeds.
Oxadiazon is a granular formula safe for all turfs and ornamentals.