How to Control Weeds When Seeding Your Lawn with Mesotrione

Planting new grass seed can feel like hitting the reset button on your lawn. Whether you’re overseeding a thinning yard, repairing bare spots, or starting a new lawn, the goal is always to give the new grass the best possible opportunity to establish. Unfortunately, weeds often have the exact same idea.

Many traditional pre-emergent herbicides are designed to prevent seeds from germinating, which can make weed prevention tricky when you’re trying to grow grass at the same time. The active ingredient, mesotrione or "meso", offers homeowners another option. It provides both pre- and post-emergent weed control and can be used when seeding or overseeding certain turf types.

Here's what homeowners should know about using The Andersons Meso 4 SC, when to apply it, and how to get the most from an application.

Mesotrione is a herbicide that is applied as a foliar application and blocks suscepitble plants' ability to photosynthesize. What makes meso particularly useful for DIY lawn care is its ability to work as both a pre-emergent and post-emergent herbicide. In other words, it can help prevent certain weeds from establishing while also controlling susceptible weeds that are already growing. Meso controls more than 50 common broadleaf and grassy lawn weeds, including crabgrass, clover, dandelion, creeping bentgrass, foxtail, ground ivy, henbit, nutsedge, and more. That gives homeowners a versatile weed-control option, but one of meso's biggest advantages comes into play when it's time to seed.

Meso can be applied, on labeled turf types, when seeding or overseeding an established lawn, including at the time the grass seed goes down. For best pre-emergent control during seeding, you should apply it at seeding or before germination. That's an important distinction from many pre-emergent strategies.

When you're establishing new grass, you need your desirable grass seed to germinate while still trying to limit competition from weeds. Meso provides the option specifically suited to that situation.

Meso can be effectively used as a pre-emergent on seed blends containing less than 20% fine fescue by weight. Applications to fine fescue can reduce grass density. Always check your grass seed label so you know exactly what species and percentages are in your seed mixture before applying any herbicide.

Timing depends on whether you're using meso for pre-emergent control while seeding or to control weeds that are already growing. If you're planting grass seed while also trying to manage weeds, meso can provide pre-emergent weed control while accommodating germination of labeled turf types. If you're not seeding, consider longer-lasting pre-emergent options such as Prodiamine or Dimension instead. Think of meso as an especially useful tool when your lawn-care goals overlap: you want new grass coming in without giving weeds free rein.

For pre-emergent applications, apply meso at the time of seeding or as close to seeding as possible. For best results, the product should be applied at seeding or before the grass has germinated. The application should then be watered in immediately. If you miss that window and your new grass has already germinated, don't immediately reach for the sprayer. In this case, you should wait four weeks after germination before applying.

Meso can also be used as a post-emergent herbicide after weeds have appeared. For best results, apply it to young, actively growing weeds. It is best practice to also use a non-ionic surfactant, such as 80/20 Select Surfactant, for post-emergent applications. After spraying, avoid watering the lawn for at least 24 hours so the application has time to dry. More established weeds can be harder to control, and another application two to three weeks later may be necessary for adequate control. Weed-control effectiveness can also be reduced when weeds are mature or experiencing moisture stress.

There's an important difference between applying meso at seeding and applying it after your new grass has germinated. Avoid post-emergent applications to newly germinated turf. Once the grass has emerged, wait until it has been mowed twice or four weeks have passed after emergence, whichever is longer, before making a post-emergent application. Giving young turf adequate time to establish can help prevent unnecessary stress on your new lawn.

Knowing where not to use an herbicide is just as important as knowing where to use it. Meso should not be applied to desirable: Bentgrass, Poa annua, kikuyugrass, zoysiagrass, seashore paspalum, or bermudagrass. Or, as a pre-emergent application, it should not be used on grass blends with 20% or more fine fescue. If you aren't sure what type of grass you have, identify your turf before applying the product.

1. Apply on a calm day. Avoid windy application conditions. Lower wind reduces spray drift and helps you get more consistent coverage where you actually want the product.

 

2. Keep your application even. Maintain steady sprayer pressure and slightly overlap your passes to create uniform coverage.

 

3. Pay attention to watering instructions. This is an easy one to mix up because the recommendation depends on how you're using the product. When applying as a pre-emergent at seeding, you should water it in immediately. When applying post-emergently to existing weeds, don't water for at least 24 hours.

 

4. Time mowing around your application. For established lawns, avoid application within two days of mowing. A good approach is to mow two days before applying meso, then wait another two days after application before returning to your normal mowing schedule.

 

5. Clean your sprayer. Rinse your sprayer thoroughly after you're finished to remove residue that could affect future applications.

Overseeding and lawn renovation already require time, water, and patience. The last thing you want is emerging weeds competing with the grass you're working hard to establish. Always read and follow the product label before use.