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.
In short, here’s what you should do if you encounter weeds in your newly seeded 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.
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.
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.
Any weeds you dig or pull up should be bagged up and disposed of carefully so they don’t have chance to spread. Also, make sure you fill in any holes the weeds leave – otherwise you will be leaving inviting homes for new weeds to occupy.
Once your new grass is more established and has been mown at least twice, you can consider applying weed killer. If you are trying to kill dandelions or other broadleaf weeds, this is the correct action to take at this stage.
The first thing to do is to make sure the grass seed you are spreading is “clean” and free of any other kinds of seeds. This will at least mean you are not spreading weed seeds when you seed your lawn.
· Don’t apply weed killer too early
For this reason, let’s start by talking about what you should do to stop the weeds taking root in the first place – after that, we can move onto dealing with weeds once they begin to appear.
Here’s a video that discusses the different types of weeds you may come across.
If you catch weeds early enough, you can keep the situation under control – but if weeds become well-established, it can be more difficult to deal with them.
If you apply weed killer before you mow your new grass twice, it will be too weak and may die along with the weeds you want to kill.