What are Pre-emergent herbicides?
PRE-EMERGENT
After a long and cold winter, the days are beginning to get a touch longer and depending on where you are, the mercury is starting to rise just ever-so-slightly as each day begins. Yes, it’s still winter and most are still covered in snow…But before you know it, we will be breaking out the shorts and getting ready to host those weekend barbecues again with are family & friends!
Weed control is a subject most homeowners are looking to tackle each lawn season. Yard work and weed control might not be the first thing on your mind as you look out onto a snow-covered lawn. Most homeowners wait until they see weeds in their lawn before they act on weed control. While that works, there are better (and more cost effective!) ways of taking control of your lawn.
Applying a pre-emergent herbicide (or weed killer) is a great strategy to take control of your lawn this upcoming season. In simple terms, these products will prevents weeds from germinating before they ever have a chance to pop up and take over your lawn.
We will break down everything you need to know about pre-emergent below.
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What are Pre-Emergents?
Pre-emergents are a type of herbicide (or weed killer) used on turfgrass that are designed to control weed seeds from germinating. In other words, pre-emergents are applied before the weeds have a chance to pop up and take control of your lawn.
How do Pre-Emergents Work?
Once watered in, pre-emergents inhibit cell division and prevent seeds from properly emerging. This is done by creating a chemical-barrier in the soil which prevents the seedlings from emerging or developing in a normal way.
What are some popular products of Pre-Emergent?
What weeds do Pre-Emergents prevent?
Most pre-emergent herbicides are targeting crabgrass prevention. While that is the most common use, there is a long list of other grass and broadleaf weeds they can help prevent.
How do I apply Pre-Emergents?
You can apply a pre-emergent herbicide in a couple different ways. For most homeowners, they are applied via a broadcast spreader as a granular application. They can also be applied as a liquid, or water-soluble application via hand-pump or battery-powered sprayer.
Pre-Emergent applications can be applied either in one application or in multiple split-applications.
All options are effective if used properly and applied at the recommended rates. If you’re looking for the most cost-effective option, this is likely achieved via a liquid or water-soluble option. We have listed a few of each option below.
When do I apply Pre-Emergents?
This is dependent on your local soil temperatures. The general rule of thumb is to get pre-emergent herbicides down on the ground and watered in before the soil temperatures are at 50-55 degrees (F) for consecutive days.
If you don’t have a soil thermometer, GreenCast is a great free online resource to help identify local temperature trends in your area.
Pre-Emergent & Grass Seed
If you’re planning on planting grass seed, pre-emergent should not be applied as most active ingredients will not differentiate a weed seed from a grass seed, ultimately killing your new grass shortly after germination.
The exception is mesotrione, the active ingredient in Tenacity. Mesotrione is a selective herbicide that serves as a pre and post-emergent for control over broadleaf weeds, meaning it can be used on most grass types at the point of seed application and/or shortly after in a split application.
Generally, applications of mesotrione are effective when applied along with the new grass seed and will likely need a secondary application 4-6 weeks after initial application.
Watch Our Pre-Emergent Episode:
Plan out your lawn season with us by subscribing to our Free Newsletter. Check out and subscribe to our YouTube Channel and follow us on Instagram.