
Weeds can be a nightmare, but knowing how to apply post-emergent herbicides properly can make all the difference. Whether you opt for a blanket or spot treatment, the following steps are key: gather your tools and materials, prepare your lawn and equipment, use the herbicide as directed on the bag, and follow some post-application steps.
How do post-emergent herbicides work?

Post-emergent herbicides target established weeds that are difficult to remove manually or with organic weed killers. The product you choose and how and when you apply it should align with the types of weeds you have.
Depending on the level of infestation in your yard, choose between blanket or spot treatments.
Blanket treatments can help if your entire lawn is overrun with weeds. Use a liquid or granular selective post-emergent to only target the weeds. Using a non-selective will kill your grass and other desirable plants along with the weeds.
Spot treatments address minor weed issues, such as small weed clusters. They work well around:
- Flower beds
- Ornamental gardens
- Sidewalks and driveways
- Trees and shrubs
- Lawn edges
- Use a liquid selective herbicide that only targets the weeds and makes it easy to apply to specific lawn areas.
My tip: Always treat the weeds when they’re actively growing. This is when they’re most vulnerable to post-emergent treatments.
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Before you start
Check the weather
Check the weather forecast and choose a calm, dry day for application (but no drought). Avoid rain for at least 24 to 48 hours after application to allow herbicide absorption.
Gather your equipment
To successfully apply post-emergent herbicides, you’ll need the right tools and materials:
- First, identify the weeds in your yard and purchase a herbicide that targets them.
- Then, gather protective gear (gloves, long-sleeved clothing to minimize skin exposure, eye protection, mask), marker flags, hose or sprinkler system, and cleanup supplies (soap, water, and possibly a change of clothes)
- Next, get what you need if you’re applying a liquid post-emergent:
- Backpack sprayer (easy to maneuver and allows for precise application), boom sprayer (can be attached to an ATV or lawn tractor for efficiency and covers wide areas faster), Hand-held sprayer, or hose-end sprayer
- Sprayer nozzle to control the spray pattern and droplet size
- Measuring cup or syringe (helps measure small, exact amounts of herbicide for spot treatments)
- Bucket for mixing the herbicide with water
- Spray shield or drift guard
- Alternatively, you’ll need the following for granular post-emergent:
- A broadcast spreader (for large areas) or drop spreader (for smaller areas)
- A broom and dustpan to pick up leftover granules from your driveway or walkway
Prepare your lawn

- Mow your lawn as usual, according to your grass type. This allows the herbicide to make better contact with the weeds. Wait a day or two after mowing to apply the treatment; freshly cut grass is more sensitive to chemicals.
- Clear the lawn of leaves, sticks, branches, and general debris to allow easy herbicide access to the soil. Debris can also cause uneven application.
- Take note of delicate plants, garden features, and sprinkler heads in your yard that could be affected by the application. You’ll want to avoid damage to them.
- Place marker flags around the yard. First, define the perimeter of the area you want to treat. Then, divide it into rows to make the application easier.
- Look at the bag or bottle to see if you need to water your lawn before application. Typically, the soil should be slightly moist to absorb the post-emergent (granular or liquid) perfectly. Weeds are also more “open” to the herbicide when the soil is moist.
The application process
Liquid post-emergent

First, mix the herbicide with the amount of water written on the label. You can use the bucket or mix the liquids directly in the sprayer. Shake or stir well before using.
Second, spray clean water over a particular area to check the output. If it’s not right, adjust the nozzle to match the recommended setting.
Then, start treatment:
Liquid blanket treatments
- Begin at the outer edge of your lawn and work your way in, spraying the product in straight rows according to the marker flags. Walk at a steady pace.
- For an even application, keep the sprayer around 2 feet off the ground at all times and slightly overlap each pass.
Liquid spot treatments
- Aim the sprayer directly at the weeds you want to eliminate. Spray them until the leaves are saturated, but avoid excessive runoff.
- Work systematically through the marked areas.
Granular post-emergent

Using the label instructions, calibrate your spreader before application. This helps you apply the correct amount of product to your lawn and avoid burning the grass. It also ensures the treatment is effective. After that, pour the granules into the spreader on a flat, hard surface to prevent spills.
Then, start treatment:
- Apply the herbicide around the perimeter of the treatment area, then move to the center in parallel passes. Walk at a consistent speed to distribute the granules evenly. Slightly overlap your passes to prevent missed spots, but avoid over-application.
- Take breaks to see if the spreader is applying the granules evenly.
Special considerations
To get the best results from your post-emergent, take a few extra steps to protect nearby plants and the environment.
Cover the entire weed leaf
For the herbicide to be fully effective, cover the weed leaves entirely. This allows the active ingredient to be fully absorbed. Missing parts of the leaf can cause some weeds to survive.
If you’re using a liquid herbicide, use a fine spray to saturate the weeds. Likewise, spread granules evenly across the target area.
Use barriers to protect sensitive plants
Herbicides can damage plants you want to keep if they touch the leaves or roots.
Before spraying your liquid post-emergent, set up barriers like cardboard, plastic, or plant covers. For granules, don’t apply them too close to the plants and water them in to stop drift.
Stop if the wind picks up
Wind can cause herbicide drift, damaging plants, polluting water, or irritating your skin and eyes.
If it picks up mid-application, stop and wait for calmer conditions to continue.
Don’t overapply your herbicide
Stick to the recommended dosage on the herbicide label; using more than necessary doesn’t improve weed control and may stress your plants, contaminate the soil, and harm the environment.
Post-application steps
You’re almost done – with a few important steps left to follow:
Keep off the treated area
Keep your little ones and pets off the treated lawn until it’s safe. Since they often play, sit, or roll on the grass, they’re more likely to come into contact with chemicals. Waiting gives the herbicide time to dry and absorb, lowering the risk of exposure.
Water the treated area
- For liquids: Only water if the packaging says so and within the timeframe indicated (usually a few hours). Not all liquid products require watering.
- For granules: Watering activates them and helps them stick. Don’t overwater, or it will wash them away.
Clean your equipment
Use soap and water to thoroughly clean the tools you used to apply your post-emergent herbicide.
Pro tip for sprayers: Weed and horticultural experts at Utah State University advise against using the same tool for herbicides and pesticides. “Some herbicides such as 2,4-D are difficult to completely remove from sprayers. Damage to desirable plants could result from a herbicide-contaminated sprayer used to apply insecticides.”
Store the herbicide
Store herbicides safely where your kids and pets can’t reach them, like in a locked cabinet or up high. Even tiny amounts can pose a risk if eaten or touched, so keep the lid on tight.
Also, store your herbicides in a cool, dry spot with some airflow. Moisture, direct sun, and extreme temperatures can make the active ingredients less effective. A shed, garage, or basement with stable temperatures is ideal.
Before storing, check the container or package for leaks or cracks. If it’s compromised, move the product to another labeled container or dispose of it as directed by local regulations.
Monitor results
Check the treated areas closely. If the herbicide is working, the weeds will start wilting, stop growing, and look discolored, indicating that the herbicide is working.
Other weeds might persist, in which case you should re-apply the herbicide according to the wait time on the label.
Maintain your lawn properly

A well-maintained, thick, healthy lawn can naturally crowd out weeds, reducing the need for herbicides. Here’s what to do:
- Mow at the right height. Cutting your grass too short weakens it, making it more vulnerable to weeds, drought, and disease. Set your mower height based on your grass type.
- Fertilize correctly. Choose your fertilizer based on the results of a soil test. Giving your lawn the right nutrients at the right time helps it grow thick and strong.
- Water properly. Water your lawn well but less frequently to promote deep root growth. Try for 1 to 1.5 inches of water per week, whether from rain or irrigation. Water in the morning to reduce evaporation and fungal problems.
- Aerate the soil. If your soil is compacted, it prevents air, water, and nutrients from reaching the roots. This causes weak grass and weeds. If you have warm-season grass, aerate in late spring to early summer. For cool-season grass, try early to mid-fall. Core aeration can also improve soil structure.
- Overseed to fill in bare patches and prevent future weeds. Match new grass seeds to your existing lawn for the best results.
FAQ about how to apply post-emergent herbicides
No, avoid applying in temperatures above 85 degrees Fahrenheit as the herbicide may evaporate or damage desirable plants.
You’ll typically see results within seven to 14 days, but it can vary depending on the weed type and environmental conditions.
Rinse the plants immediately with plenty of water to dilute and remove the herbicide.
The University of Florida IFAS Extension says weed and feed should only be used when weeds cover the entire lawn evenly, which is rarely true. Some homeowners also use the herbicide component as a pre-emergent.
That said, a mix of herbicide and fertilizer usually won’t fully eliminate weeds.
Keep weeds out of your yard
Managing weeds on your own is simple, but not everyone is ready for the task. If you’re in that boat, a local weed removal specialist can take over and make sure your yard meets your expectations.
Plus, Lawn Love can connect you with a local lawn care expert who can maintain your lawn so you can prevent future weed infestations.
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Main Photo Credit: Tomasz Zajda | Adobe Stock Free | License