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.
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.
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.
Weed Control after Seeding
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.
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.
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.
Herbicides and Seeding
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.
It might be tempting to apply weed killer the moment you see that first weed pop out. However, if you use weed killer on newly seeded lawn that isn’t mature enough, the grass and weeds may die. It is a much better approach to remove the weeds one by one if there are only a few weeks.
You can think about using weed killer after giving your lawn enough time to mature, allowing for at least two mowings. If you encounter issues with broadleaf weeds like dandelions, this is the right course of action to take now.
A safe way to remove weeds is to take hold of them at the base and then pull up slowly. Avoid tugging too harshly because you don’t want to remove only part of the weed while leaving the roots firmly in the ground. If the roots or even just parts of the roots remain, the weed will continue growing. So instead, you want to remove the entire weed.
It is not a good idea to place the removed weeds in your composter because you could risk spreading weed seeds.
4. Use a post-emergent weed killer after the second mowing of your lawn.
If you are struggling with more extensive roots, it might be helpful to use a hand shovel first. You can use it to dig around the weed, making it easier to remove the entire weed.
Not all of us are born with green fingers, and for some of us, it can be challenging to have something as ordinary as grass grow well. Have you ever started a newly seeded lawn only to be disappointed when it was infested by weeds a few weeks later?
The seed you choose is essential here because you want to choose seeds that won’t contain any weed seeds. By selecting seeds that are free of any other seeds, you avoid the possible spreading of weed seeds while you are seeding your lawn.
5. Issues with crabgrass
What should you do to prevent weeds from rooting?
It is crucial that you follow the correct practices to keep your seedlings healthy. This includes keeping your seedlings watered and fed. You should always avoid cutting them too early or too short. By providing the best possible beginning to your seedings, you make it very challenging for weeds to invade.