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 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.
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.
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.
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.
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.
In short, here’s what you should do if you encounter weeds in your newly seeded lawn:
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.
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 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.
If the grass you used is warm-season grass like Bermuda, a combination of 2,4-D, dicamba, and quinclorac mixed in herbicide can effectively kill weeds without harming your grass.
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You can also take advantage of this by allowing the weeds to grow before seeding your new lawn. Afterward, kill the weeds with a non-selective (kills all plants that it comes into contact with), weed killer, like RoundUp, and lastly, sow your grass seeds. The weeds that appear after this process will be young and easier to control. RoundUp contains a chemical called glyphosate.
How Long After Seeding Should You Spray For Weeds?
Post-emergent herbicides are herbicides used after weeds have emerged and not before. The weed killer you buy comes with instructions on the label, which you must read carefully. The brand also contains the application process.
Pulling weeds can only be successful if weeds are not out of control. A weed infestation requires a more aggressive approach to kill them. You can also choose to dig up weeds that aren’t easy to pull out using a spade.
I have employed both tactics on my lawn, and I have no complaints. You can try the same and share with me the results. Using the different methods of killing weeds can make you an expert.
Regular mowing of grass can help you get rid of weeds; they die when you cut the grass. You should also only mow your lawn when the soil is dry.