If you’re looking to upgrade your spring gardening toolkit and haven’t yet tried pre-emergent herbicides, this may be a good place to start. Pre-emergent herbicide is a type of weed killer that works by preventing seed germination. That means you have to apply it before weeds appear.
How Does Pre-Emergent Herbicide Work?
Pre-emergent herbicides work by creating a chemical barricade in the top layer of soil that coats seeds and prevents them from growing roots and shoots. Though pre-emergent herbicides work on many types of lawn weeds, they’re most commonly used to reduce crabgrass. The active ingredients in herbicide are dithiopyr, isoxaben, and prodiamine, which help with multiple weeds and crabgrass control.
Read our article to access our guide on eradicating crabgrass.
What To Buy
To figure out which type of herbicide weed preventer to buy for your summer annual and winter annual weeds, you’ll want to take note of what type of existing weeds tend to grow on your lawn. The same variety of weeds typically pop up year after year, so noting the types of weeds that sprout on your lawn can help you figure out which type of pre-emergent herbicide to buy the following season. Your local garden store can help you determine which herbicide will target your weeds.
Keep in mind that no pre-emergent herbicide can target all varieties of weeds. Some pre-emergent herbicides kill a broad array of common lawn weeds while others target specific weeds like crabgrass or chickweed.
To target the spectrum of weeds present on your lawn, Oregon State University recommends using two types of herbicide, such as one that controls turfgrass weeds and another that controls broadleaf weeds.
You’ll also need to decide whether you want to use a liquid or granular pre-emergent herbicide. Liquid herbicides should be mixed with water (if sold in a concentrated form) and applied with a sprayer, which you can either buy or rent. With granular varieties, you can apply by hand or with a spreader or shaker bag.
Water your lawn within a few days of application for the herbicide to be effective, as the water allows the herbicide to spread deeper into the soil. Most pre-emergent herbicides are chemical-based, but there are a few natural and organic varieties available. Before applying, know that diluting the herbicide more than the recommended amount can greatly reduce its efficacy. For this reason, it’s important to apply the herbicide according to its directions.
If you wish to explore natural and organic herbicide options, we recommend you to read our article on how to make organic herbicides.
When To Apply a Pre-Emergent Herbicide
Apply a pre-emergent herbicide in the early spring, a few weeks before annual weeds typically appear.
If you’re new to the region or simply unsure when lawn weeds first pop up, a good rule of thumb is to apply your herbicide once the weather reaches between 65 and 70 degrees Fahrenheit for at least 4 days in a row. You can also seek advice from a local gardening center or university cooperative extension.
Many people apply a pre-emergent herbicide for a second time about 6–8 weeks after the first application. Read the label to find out more about when to best apply.
Fall Pre-Emergent Application
While it is not necessary, you can apply a pre-emergent herbicide twice a year — in the spring and fall — to help prevent a weed-invaded garden. I do this with my lawn, and it seems to work well in preventing weeds from coming back. You’ll want to wait until the temperature drops below 70 degrees Fahrenheit before applying, which is generally in September or October.
Things To Keep in Mind
- Don’t wait too long — This variety of herbicides will not be effective if weeds emerge before application. It also won’t be effective if applied too early, as rain can cause the herbicide to be washed away or travel too deep into the soil. But if you’re really unsure of when to apply your herbicide, it’s better to apply too early than too late.
- Maintain undisturbed soil — Aerating your lawn or cultivating it in any way can disrupt the top layer of soil where the herbicide has created a barrier. After applying pre-emergent herbicide, avoid digging or doing anything else to disturb the top layer of soil.
Buyers Guide: Pre-Emergent Herbicides
There are many pre-emergent herbicides on the market, so it can be difficult to choose the right pre-emergent product for your lawn. When purchasing the best pre-emergent herbicide for you, there are some factors to consider.
Price
The cost of a pre-emergent herbicide can be a huge deciding factor when choosing the right product. While a $100 bottle of herbicide seems like a big expense at first, it will last longer and cover more area than a small $25 bag. Paying more for the product in bulk can save you money in the long run, as you don’t need to keep going out and purchasing more herbicide.
Region
Depending on where you live, you might need to look into different options. If you live in an area that gets a lot of rain, a liquid pre-emergent will work faster and stay in the soil longer. There are some granule pre-emergents that work well with rain or snowfall, so it is best to look into the specifics before purchasing a product.
Equipment
If you use a liquid pre-emergent herbicide, you will need to also purchase a pump sprayer for your herbicide applications so you can evenly coat your lawn. A good pump sprayer can cost up to $100, so you should keep the price of additional equipment in mind before purchasing a product.
FAQS
Is pre-emergent a weed killer?
Pre-emergent does not kill weeds that have already come out of the ground. Instead, it prevents weed seeds from germinating, stopping any new weed growth.
Is pre-emergent worth it?
Pre-emergent is known to be effective in preventing certain weeds from overtaking your lawn. If you properly apply it, it is definitely worth it, since it prevents weeds from spreading. It is a good crabgrass preventer and also works well in preventing dandelions, fescue, spurge, bluegrass, foxtail, and nutsedge from spreading.
What is the difference between pre-emergent and post-emergent?
While pre-emergent means that it prevents weeds from growing within the soil, post-emergent herbicide means that it kills the weeds after they have already come out of the ground.
Not Interested in DIY Landscaping?
As a homeowner, lawn care is more than just weed control. The best lawn care services, like TruGreen, offer additional services like fertilization, weed control, aeration (check out key insights on lawn aerators), seeding, and more. Trugreen is our top recommended provider for all of your lawn care needs. To get a free quote, fill out this form or call 1-866-817-2172.
To learn more: TruGreen Review
Compare these top lawn weed control services:
- TruGreen vs. DIY lawn care
- TruGreen vs. Sunday Lawn Care
- TruGreen vs. Weed Man
- TruGreen vs. Lawn Doctor
Final Thoughts
Weeds not only look bad, but they make it difficult for you to grow the plants that you want. Pre-emergent weed control is an affordable and effective way to take care of weeds that take over your lawn. However, DIY landscaping isn’t for everyone. Whether you choose to manage the weeds on your own, or get help from an expert, you have options.
