Weed management should be completed before seeding the lawn with a non-selective herbicide seven to 14 days before you till the soil. A second application of the herbicide may be required to kill any weeds you missed during the first treatment. Wait another seven days until tilling the soil if a second application is used.
A general rule of thumb is to wait at least until you have mowed the new grass four times before using any standard postemergent broadleaf herbicide. A standard pre-emergent herbicide should not be applied until at least three to four months after seeding the area.
Some pre-emergent herbicides can safely be used during seeding and usually come mixed with a seed starter. These products have the active ingredient Siduron – also known as Tupersan – that works by suppressing weed seeds while improving root development of the new grass. The fertilizer and pre-emergent herbicide mix is applied with a drop or rotary spreader using a rate of 2 1/2 pounds per 1,000 square feet. The spreader setting and actual application depends on the brand of starter fertilizer plus weed control you use, and you should always follow the instructions found on the label.
Weed Control after Seeding
Before you plant grass seed, you should always prepare the area by removing any weeds that may be growing in the location. Even with careful preparation of the planting site, weeds can still develop among the newly planted grass seed. Weed killers, however, can harm grass seeds and seedlings if applied too early or improperly.
You can control weeds in newly planted grass seed and seedlings without the use of herbicides. Manually pulling the weeds by hand when they first appear keeps them from producing seeds and prevents the problematic plants from spreading, according to the University of California Statewide Integrated Pest Management Program website. They suggest keeping the newly planted grass weed free with proper mowing, irrigation and fertilization. Since newly planted turfgrass has short roots, keep the root zone moist by watering the soil lightly. However, avoid over saturating the soil. After the turfgrass has become established, promote deep and healthy root growth by watering infrequently but deeply.
Remember that all herbicides are different and the exact time you must wait to apply weed killers to newly planted grass will vary from one product to another. Also, some herbicides cannot be applied to certain species of turfgrass. For best results, always refer to the herbicide bottle’s label.
Marylee Gowans has written about gardening for both online and print publications. She attended the University of Akron, graduating with a Master of Fine Arts in creative writing. In 2009, she received master gardener certification from the Master Gardeners of Summit County, Ohio.
In short, here’s what you should do if you encounter weeds in your newly seeded lawn:
However, you can get rid of these weeds just as fast as they have appeared.
The important thing to remember when new weeds appear in your newly sown lawn is not to act hastily – do not apply a Feed, Weed and Moss Killer type product of any kind on a newly sown lawn.
Although this can be frustrating and we can appreciate that a quick solution will be desired, the good news about these types of weeds is that they are largely shallow rooting and should come out with the first mow at the 6-8 week mark after sowing. If they don’t, they should be easy to pull out of the turf.
If you find that the weeds are recurring past the 6-8-week mark, you may wish to consider using a selective herbicide to spot spray your weeds. Some weed killers such as glyphosate (Roundup) kill more than just weeds, so it is important to not apply these as if they are not done precisely, they can kill your grass. Shop bought selective weed killers will recommend when to apply their product and how often and you should read the instructions thoroughly and adhere to them.
If you find that when the lawn is at least six months old and has been taken over by weeds or moss, you can use a Feed, Weed and Moss Killer product.
Knowing your total property size is just the start. All non-lawn areas must then be deducted. This includes the footprints of your house, garage and outbuildings, as well as walkways and the driveway. Only then can you calculate your actual lawn area and the amount of seed you need. Time spent on proper measurements prevents wasted product, wasted money and poor results. Get it right and every bit of seed and labor work in your favor.
Getting your seeding rates right requires knowing the correct size of the area you need to cover. One of the most common problems grass professionals see is when homeowners misjudge their actual lawn areas and over-apply grass seed or other products, such as fertilizers and herbicides.
One of the ways weed treatments work is by preventing germinating seeds from establishing roots. But these products, known as pre-emergents, can’t distinguish between harmful weed seeds and desirable grass seed you put down. Using these products too close to newly planted seed — in timing or proximity — stops grass seed in its tracks, along with the weeds. Post-emergent weed treatments aimed at existing broadleaf weeds can also injure immature grass seedlings.
4. Ignoring recommended seeding rates
Seeding success depends on an environment conducive to good grass growth. Knowing how your soil measures up on certain essentials, such as soil pH and plant nutrients, allows you to provide the foundation an outstanding lawn needs. Soil testing processed through a reputable soil laboratory eliminates guesswork and reveals changes you need to make.
When it comes to your lawn aspirations, you can bypass common grass seed mistakes and head straight for success. Make the most of your investment of time, money and grass seed, and enjoy the exceptional results. Pennington is committed to helping you grow the finest lawn possible and enjoy all the benefits that a beautiful, healthy lawn holds.
Without knowing where your soil stands, well-intended soil amendments and fertilizers can harm grass instead of help — or simply go to waste. Incorporating your specific soil lab recommendations helps circumvent potential problems and unnecessary setbacks. That’s one reason turf professionals emphasize regular soil testing to start seed right and keep lawns healthy and vibrant. Your local county extension office can help with testing kits and lab referrals.
Many homeowners think lime is a lawn care necessity, but that doesn’t hold true across the board. Normal lawn care can naturally cause soil pH to drop lower over time, and lime applications benefit lawns that need pH raised. But in some cases, soil pH may already be high. Using too much lime or applying it unnecessarily can be as damaging as failing to add lime when it’s needed.