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.
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.
By properly maintaining your lawn, you can avoid the growth of weeds and enjoy lush, beautiful grass. Keep your lawn watered and fertilized if appropriate. Knutsen suggests fertilizing a new lawn between four and six weeks after you plant it. They also suggest that if weeds do crop up before the four to six weeks are up, you can remove them around the eight- to 10-week mark.
Keep gardens and wooded areas clear of weeds whenever you can to prevent the spread of weeds into your newly reseeded lawn. If you notice that weeds are beginning to encroach on your grass, pull the weeds as quickly as possible.
Grass with healthy root systems that is thick and fills the space available will act as its own line of defense against invasive weeds. When you see weeds in an established lawn, remove them individually as quickly as possible. This will help lessen the spread.
Avoiding Future Weed Growth
Weeds in new turf may also be the result of low-quality grass seed. Believe it or not, some products may contain seeds for weeds in addition to the grasses they purport to have. Check the package of your grass seed carefully and ensure that it says “weed seeds 0 percent” before you apply it to your yard. This will give you the best shot at a weed-free lawn.
Growing the perfect lawn takes time and patience and is not a small financial investment. It can be extremely frustrating when just after you’ve finished reseeding your lawn, weeds in new grass begin to peek through. Using weed killer is not the best idea when you are also dealing with fledgling grass, however. You are better off dealing with weeds individually so as to protect the grass around them.
Depending on the types of fertilizer you’ve used and the potency of the weeds in your lawn, you may find weeds in a newly seeded lawn fairly quickly. One way to prevent this is to carefully remove all existing grass, weeds and topsoil before applying new topsoil and grass seed. Unfortunately, weed pieces and seeds can easily be left behind in the dirt if you do not thoroughly clear your lawn before applying new seed.
If you decide to treat the weeds with chemicals, start by applying the substance to each weed or patch of unwanted growth rather than to the lawn as a whole. This will save as much of your lawn as possible from being overtaken by weeds.
As your new lawn becomes established, you can start easing up on the water, depending on the weather. If you continue your everyday watering routine, you’re likely to overdo it and rot the young seedlings. Also, if the ground is too wet, you can inhibit root growth.
This may be the most important step. With the first watering, make sure that you apply enough water to wet the soil down to at least 6 to 8 inches. Apply the water gently so that you don’t wash the seed away or create puddles.
Watch the color of the soil surface. As the soil dries, the surface becomes lighter in color. When you notice about half to two-thirds of the surface lightening up, it’s about time to water.
Caring for your new lawn after germination
If the grass doesn’t dry out, keep stretching the intervals between watering until you’re on a schedule of once or twice a week, or as needed. When you do water, don’t forget to water deeply, getting the moisture down 6 to 8 inches.
You will need to mow the new lawn when it reaches 3 to 4 inches high, depending on the type of grass. Mow when the soil is on the dry side; otherwise, you might tear up the new turf. Make sure not to have your mower set too low. It is always good to mow grass at 3 inches or higher to prevent it from drying out. This is especially true for your new lawn.
You may have to water several times in short intervals until the bed is thoroughly wet. After that, water often enough to keep the top inch or so of the seedbed moist until the seed germinates. Remember, seeds get only one shot at germination. If you let them dry out, they will die.
Sprinkle the seedbed lightly with a handheld hose several times a day — especially if it’s hot or windy — to get even germination across the entire lawn. However, you don’t want to overdo it. Too much water causes the seed to rot.