If weeds take over your lawn, get ahead of them and know how to apply pre-emergent herbicides. The two types of herbicides – liquid and granular – target the weeds you’re dealing with but are applied differently.
We’ll guide you on the step-by-step application process for both liquid and granular pre-emergent herbicides.
What are pre-emergent herbicides?
Pre-emergent herbicides deprive weed seeds of nutrients and build a chemical barrier in the soil’s surface. This disrupts root growth and plant establishment. To be effective, NC State Extension says the herbicide must be present in the soil at the time of weed germination.
The type of pre-emergent you choose should align with the weeds you’re trying to prevent and your long-term lawn care goals. The best pre-emergent for you might not be the best for your neighbor.
Guide to applying pre-emergent herbicides
To apply pre-emergent the right way, consider its form: liquid or granular.
Liquid herbicides cover large areas quickly and are absorbed faster, but require product mixing. In contrast, granular herbicides involve little measuring and cost less, but require a spreader and some talent for an even application.
While granular herbicides are often preferred for pre-emergent weed control because they stay on the soil surface and prevent seed germination, liquid formulations can also target seeds in the soil. Both types can be effective when used correctly, according to the manufacturer’s instructions.
How to apply liquid pre-emergent herbicides
Tools you’ll need:
- Liquid pre-emergent of choice
- A sprayer. Most liquid pre-emergents come with a sprayer tool, but you can also purchase one separately. Backpack, hand-held, and hose-end sprayers are all options.
- Measuring cup
- Water source (to dilute the herbicide and clean the spreader after application)
- Measuring tape
- Marker flags
- Chemical-resistant gloves
- Work clothes with long sleeves
- Protective eyewear
Preparation:
- Check the weather forecast. Make sure there is not rain or wind in the forecast to wash away the product or make application challenging.
- Prep the mixture: Measure the length and width of the lawn and multiply the numbers to get the square footage of your lawn. Check the result against the application rate on the label.
Example: If your lawn measures 5,000 square feet, and the label says 2 ounces of herbicide per 1,000 square feet, divide 5,000 by 1,000 and multiply that by 2. This is the amount of herbicide needed for your lawn.
- Mix the herbicide with the recommended amount of water.
- Mark the area you want to treat to prevent excessive overlap or missed spots. Insert marker flags in rows to help.
- Gear up.
Application:
- Apply the herbicide to your yard row by row, just as you would mow your lawn. This helps you apply the product evenly.
- Maintain a steady pace and keep the sprayer nozzle close to the ground to minimize drift. Overlap passes slightly.
Post-application:
- Wait 12 to 24 hours for the liquid to be absorbed. Then, resume your normal watering schedule.
- Dispose of any leftover herbicide according to local regulations and guidelines.
- Rinse the sprayer with water to remove as much of the herbicide as possible. Add some mild detergent or liquid soap to the container and fill it with water. Shake it well. Follow up with a final rinse. Repeat this process as many times as needed.
- Monitor the treated area for any weeds. If necessary, reapply the herbicide as recommended on the label.
How to apply granular pre-emergent herbicides
Tools you’ll need:
- Granular pre-emergent of choice
- A broadcast spreader, drop spreader, or hand-held spreader
- Measuring tape
- Marker flags
- Broom or leaf blower
- Chemical-resistant gloves
- Work clothes with long sleeves
- Protective eyewear
Preparation:
- Measure the area you want to treat and mark it to make application easier.
- Fill your spreader with the recommended amount of granules.
- Calibrate the spreader according to the instructions. Test it on a small area.
- Choose a crank speed on your spreader. The faster the crank speed, the wider the throw distance of the granules, and the more area you can cover.
- Gear up.
Application:
- Walk at a steady pace, pushing the spreader across the lawn. Overlap each pass slightly to prevent gaps (even if you have markers down).
- Cover the entire lawn. In tough-to-reach areas, such as edges and corners, use a hand-held spreader. You can also hand-sprinkle the granules, tossing them in a controlled manner.
Post-application:
- To activate the herbicide, give the treated area the recommended amount of water. Most granular herbicides need about ½ inch of water to activate (either through rainfall or irrigation), but always check the label for specific instructions.
- Clean the spreader to remove leftover herbicide and store it in a safe, dry place.
- Sweep hard surfaces like driveways or sidewalks to clear any granules.
- Keep an eye on the treated area and re-apply the herbicide as needed and instructed.
Tips for applying pre-emergent herbicide
To successfully control weeds, use these additional tips and tricks:
- Avoid combining pre-emergent with other lawn care products, such as fertilizer. This may hinder its performance.
- Don’t sod or overseed right after treatment. Pre-emergent persists in the soil for three to four months, so that’s how long you should wait before laying down sod or overseeding. Otherwise, the pre-emergent will interfere with sod rooting or seed germination.
- Ensure proper soil conditions.A soil pH of 6.0 to 7.0 is ideal and not too much organic matter, as it can reduce herbicide effectiveness. Also, for best results, check that your soil isn’t compacted.
FAQ about how to apply pre-emergent herbicides
Are pre-emergent herbicides generally safe for turfgrass?
Applying pre-emergent herbicides on grass is OK. The only exception is if your turf has been damaged by drought, diseases, or pests, and is struggling to grow. Applying chemicals to stressed grass can make the problem worse.
When should I apply pre-emergent herbicides?
If you want to know when to apply pre-emergent, figure out what weeds grow in your yard and what time of year they grow. Ground temperature also has to be just right for weed killer application, and the perfect weather conditions.
What’s the difference between pre-emergent and post-emergent herbicides?
Pre-emergent herbicides build a chemical barrier in the soil that prevents weed seeds from germinating. Post-emergent herbicides kill existing weeds that have already emerged and are actively growing.
Is pre-emergent the best line of defense against weeds?
Pre-emergent can help prevent weeds. The University of Georgia Extension says the first line of defense is following proper lawn care practices. Build a healthy, dense, weed-free lawn by proper mowing, fertilizing, controlling diseases and pests, and using the right grass type for your region.
Keep your yard weed-free with a pro’s help
Using pre-emergents is a fairly simple process, but it’s not always smooth sailing. If you don’t have time, Lawn Love can connect you with an expert near you for help.
Also, don’t forget about other lawn care tasks necessary for a healthy lawn. A local lawn care professional can aerate, dethatch, fertilize, and mow your lawn to defend against weeds.
Main Image Credit: Kritchai | Adobe Stock | License
