Post-emergent herbicides kill weeds once they’ve sprouted in your yard, but which pre-emergent is right for your lawn? Granular or liquid? Selective or non-selective? We’ll help you sort out all of that.
You can break down the types of post-emergent herbicides into three categories: systemic vs. contact, selective vs. non-selective, and liquid vs. granular.
- Liquid and granular are the two forms of post-emergent herbicides.
- Selective and non-selective refers to the weed or plants to be killed.
- Contact and systemic treatments determine how the weeds are killed.
But which post-emergent herbicide will work best for your yard?
Liquid vs. granular post-emergent herbicides
Post-emergent herbicides are either liquid or granular. Each has its advantages and disadvantages, but granular usually is the more expensive method because you’ll use more herbicide to cover your whole lawn or yard.
Liquid post-emergents
Liquid post-emergent herbicides need to be mixed with water, and the label on your product should tell you the exact ratio. Then pour your liquid post-emergent herbicide in a backpack sprayer or hand pump, whichever you believe will give you more control for the most even application.
Advantages
- Liquid post-emergents stick to the weeds, can be applied when leaves are wet or dry.
- Easier to control and get an even application
Disadvantages
- Requires exact measurements to ensure the correct ratio between water and liquid formula.
How to apply a liquid pre-emergent: Spray over weeds as evenly as possible without going overboard. (Note: It can be easy to apply too much or too little liquid herbicide.)
Bottom Line: Liquid post-emergents adhere to plants better, making them an excellent option for killing weeds.
Granular post-emergents
Granular post-emergent herbicides look like pellets. You can either spread these with a push spreader (like a wheelbarrow with holes), a handheld spreader, or with an expensive but accurate ride-on spreader. To ensure you get an even application, walk or ride back and forth, passing over each weedy area with your spreader.
Advantages
- No measurements are needed. Simply place the herbicide in a spreader.
- Granular herbicides are the easier option for beginners.
Disadvantages
- Granular herbicides alone don’t easily stick to weed leaves.
- The ground needs to be pre-wet for some granular herbicides to be effective.
- Some spreaders to apply herbicides can be expensive.
Bottom Line: Granular herbicides are great for beginners because they require less prep time and fewer math calculations.
Systemic vs. contact post-emergent herbicides
Would you prefer to kill your yard’s weeds on contact, or would you rather a slower but more thorough approach of poisoning the invasive plant from its roots to its leaves? That’s the central difference between contact and systemic post-emergent herbicides.
Systemic post-emergents
Systemic post-emergents take longer to work than contact treatments because they kill the weed and its root system, so you won’t have to worry about them sprouting again later.
Advantages
- Kills the entire plant, from bottom to top.
Disadvantages
- Takes at least seven days to work.
Bottom Line: Systemic herbicides work best on perennial weeds like ground ivy and dandelions because their roots are already established and have most likely survived through the winter.
Note: Most selective herbicides are systemic.
Contact post-emergents
Contact post-emergent herbicides kill weeds on contact (hence the name). How do they do this? Contact post-emergents keep weed leaves from photosynthesizing, which kills the plant but not the roots. What this means: The weed may spring anew next season.
Advantages
- Prevent the weed from photosynthesizing
- Work best as a spot treatment
Disadvantages
- Don’t kill the root of the weed, so it may sprout again next season.
Bottom Line: Contact herbicides work well on small annual weeds like nettle and crabgrass as the death of their leaves is enough to destroy these plants, unlike their tougher perennial counterparts.
Pro Tip: Contact post-emergents work well as a spot treatment to cover any missed spots after applying a pre-emergent herbicide.
Non-selective vs. selective post-emergent herbicides
If you are fighting just one type of weed in your yard — or even a few types — look for a post-emergent that will kill only that one or a few types of weed. That’s the key difference between selective and non-selective weed killers.
Non-selective
A non-selective post-emergent herbicide will kill everything in its path, including flowers, bushes, and even grass. These indiscriminate herbicides work well to control weeds around fences, in driveway and sidewalk cracks, or across large areas.
If you’re not sure what kind of weeds you are dealing with and don’t want to do some basic research online to identify your weedy foes, applying a non-selective herbicide should get rid of the whole army of leafy lawn invaders.
Advantages
- Works well around cracks, driveways, and sidewalks
- Works in one treatment
- Good if you’re planning on reseeding an entire area
Disadvantages
- Kills everything it comes into contact with
- Can be highly damaging to your property if not applied correctly.
Bottom Line: Non-selective post-emergents work best as a blanket treatment. For example, you can spray your entire lawn and reseed or replant it once the area has recovered.
Selective
Selective herbicides work only on the weed — or weeds — they are designed to kill. What this means: If you mistakenly spray or spill a selective post-emergent on grass or plants, it won’t kill that greenery.
Advantages
- Works only a specific weed or weeds
- Suitable for small areas or yards
Disadvantages
- Not a good choice for blanket treatments
- May take more than one application to be effective
- Takes more time to work than non-selective treatments
- More expensive
Bottom Line: Selective pre-emergents work best in locations where you can determine the type of lawn weeds you have and where you can’t avoid turfgrass and other vegetation.
Common chemicals in post-emergent herbicides
Each ingredient in post-emergent herbicide can kill a specific type of weed, and knowing what weeds you have can help narrow down which one will work best on your lawn. Note that a post-emergent herbicide can include one or multiple ingredients.
- Fluazifop: Works best on grassy weeds like crabgrass, witchgrass, barnyard grass, and foxtail weeds. It struggles to kill broadleaf weeds.
- Dicamba: Works best on broadleaf weeds like dandelion, clover, spurge, thistle, and knotweed.
- Glyphosate: Works best on every type of plant and can kill grassy weeds like crabgrass, broadleaf weeds like dandelions or thistle, and turfgrass like bluegrass.
- Glufosinate: Works best on yellow nutsedge, creeping bentgrass, foxtail, garden spurge, ground ivy, and carpet weeds. This is a good option if you have weeds that have developed a tolerance to Glyphosate.
- Methanearsonate: Works best on crabgrass and nutsedge.
- Bentazone: Works best on yellow nutsedge, annual nutsedge, and perennial kyllinga.
Non-chemical post-emergent herbicides
Did you know some essential oils can kill weeds? For example, peppermint, winter savory, anise, and lemongrass are effective at killing newly sprouted broadleaves like chickweed, clover, and black nightshade.
How to choose the best post-emergent herbicide for your lawn
With so many different post-emergent herbicide options to choose from, it can be challenging to find the right one for your lawn.
The best way to choose a post-emergent herbicide is to assess:
- The types of weeds you have
- The size of the area where the weeds are
- How durable the weeds are
- How much prep time you’re willing to invest
Answering these questions can help you narrow your selection to choose the right post-emergent for your yard, save you time and money, and ensure you kill only the invasive plants on your property.
So what’s next?
Now that you know what types of post-emergent herbicides are out there, you’re ready to go shopping! Check out the best post-emergent herbicides to figure out which product is right for your needs. Once you’ve selected a product, you’ll need to know how and when to apply post-emergent herbicides.
And ahead of the next grass-growing season, you also may want to apply a pre-emergent herbicide to kill weeds below ground at seed level.
And if weeds have taken over your yard and you don’t have the time or energy to apply a post-emergent herbicide yourself, a Lawn Love lawn care pro near you is ready to take on the job.
Your yard deserves the best care, and with Lawn Love, we make lawn care easy.
Main Photo Credit: Shutterstock
