Many gardeners aren’t sure how long to wait before they can apply weed to their lawns after they have planted grass seed. The other issue could be the time it takes to plant grass seed after applying weedicide and feed. Both concerns can be answered by comparing the types of herbicides in various weed- and feed-products.

Can you grow weeds and eat grass seed?

After noticing a few weeds on your lawn, you may feel the urge to spray them and feed it. The herbicide will kill the seedlings. You should wait until your lawn has established before you use a weed-feed product that contains a post-emergent herbicide. Some weed and feed products can also be used to prevent weed seeds sprouting. They will kill both the grass and weed seeds if they are applied to a newly seeded lawn. Spot treatments are an alternative method to control weeds in lawns. If the infestation is still early, you can manually remove the weed plants.

Newly-established lawns can also benefit from mowing. The grass becomes stronger and draws out more weeds. It is best to wait until the third mowing to spray weeds and then feed your turf. The grass will then be strong enough for herbicides. Even then, it is important to only use a selective weed- and post-emergent weedicide. These can be used to kill broadleaf weeds such as clover and dandelions, but they won’t harm your turfgrass. Pre-emergent herbicides won’t work on already existing weed plants, while non-selective/systemic herbicides will kill both the weeds and your growing turfgrass.

When should you plant grass seed after weeding and feeding?

The time it takes to plant grass seed is determined by whether the feed or weed contained a pre-emergent, systemic herbicide. You can plant grass seed in two weeks for weed and feed products that contain systemic, post-emergent weed killers. This is because systemic herbicides do not leave any residue in soil that could cause damage to seeds that are planted a few days later. Instead, they are absorbed by the roots and leaves of the plants, killing them all within seven days. Glyphosate and pelargonic acids are two common systemic herbicides. Pre-emergent herbicides are designed to prevent seed germination. They form a chemical barrier on top of the soil. Pre-emergent herbicides are designed to prevent grass seeds from sprouting if they are applied soon after weeding.

After applying a pre-emergent herbicide and feeding to your lawn, it may take between 6-12 months before you can seed it. The average wait time is 2 months. Because of the variability in how long it takes for different pre-emergent herbicides in soil to degrade, this is possible. While a herbicide such as 2,4-D can be degraded in four weeks, you might need to wait six months before you can plant grass seed on a lawn that has been treated with Atrazine herbicide. You should note that some weed and feed products can be used to suppress weed seed without affecting grass seeds. These products often contain siduron which is a pre-emergent herbicide, which also increases the germination rate of grass seed. You can sow grass seed immediately after you apply your pre-emergent herbicide or feed if siduron is the primary active ingredient.

Important: Make sure to read all labels on your weed and food products. This will give you information about how long it takes to start grass seed. The manufacturers will usually recommend a wait time based on the type of herbicides used in the product.

How soon after you have sown the seeds can you spray for weeds again?

It is not unusual to see weeds growing alongside your grass seedlings. After three mowings, the best time to apply selective weedicide and feed your lawn is after seeding. The grass has reached this stage and is mature enough for the harsh chemicals contained in weedicides to be able to withstand them. If the weed infestation has not yet reached its peak, you can spray a pre-emergent herbicide. If you notice weeds growing on your turf, this is a sign that there are more weed seeds in the ground. After the seedlings have grown, you should spray a preemergent no later than 14 days. You should only target weed seeds that aren’t yet sprouted.

Warning: Do not use non-selective herbicides on your lawn. It will kill any plants it comes in contact with, including the grass.

Weed Control Tips After Seeding a Lawn

After seeding your lawn, you can prevent weeds from growing by using the right watering, fertilizing and mowing techniques. This will help your turf grow stronger and be able to withstand weeds.

  • Proper watering encourages deeper rooting. This helps the turf grow denseer and chokes out weeds. After seeding, you should water your lawn gently and often. After the turf is established (usually within 2 weeks), you can reduce the frequency of irrigation but continue to water the grass longer each session.
  • Fertilizing– fertilizing new turf at the right time will help it become more resilient to weeds. A new lawn should be fertilized 6-8 weeks after it is planted. Fertilizer can burn young seedlings so don’t start fertilizing too soon.
  • Mowing –mowing at a proper height and time encourages dense growth and faster turf recovery. You should trim your grass blades to a maximum of one-third of their total length. This will allow grass to enjoy the benefits and still retain enough grass blade surface to enable photosynthesis.