How to Control Weeds After Overseeding

Overseeding is an effective way to thicken a lawn and repair thinning areas. It also improves the long-term health and resilience of your grass. 

That said, once you start the process, weeds are inevitable. 

Weed control after overseeding requires care and patience. 

You will need to protect the grass as it germinates, yet you can’t allow weeds to take over vulnerable areas. 

The key is knowing which strategies are safe, which treatments are effective, and when it is appropriate to apply these treatments.

Here are seven ways to control weeds after overseeding.

1. Understand Why Weeds Appear After Overseeding

Weeds appearing after overseeding are normal and expected. 

This happens primarily because the soil has been exposed, and all the raking, aeration, and preparation that help new seeds take root, also create conditions for dormant weed seeds to germinate. 

The weed seeds are already in the soil. The overseeding process simply wakes them up.

2. Avoid Most Herbicides Right After Overseeding

New grass is extremely sensitive. Many weed control products can kill your grass in the seedling stage. The trick is to only apply weed control products at the appropriate times.

1. Post-emergent weed killer: Wait a minimum of three to four weeks after the new grass has fully germinated. 

2. Pre-emergent weed control: Never apply pre-emergent at the same time as overseeding. Pre-emergent prevents all seeds from germinating, whether they are weed seeds or healthy grass seeds. Wait a minimum of six to eight weeks before applying.

3. Herbicide: A general rule to remember is that if the grass hasn’t been mowed at least two or three times, then it is too early for any type of herbicide.

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3. Focus on Watering and Mowing First

While overseeding, your main priority should be watering and mowing before reaching for weed control products. Create the conditions that promote healthy and strong new grass. Strong grass is naturally better at keeping weeds out.

• Watering: Keep the soil consistently moist, but not soaked, during germination. 

  • As the new grass grows, gradually reduce the frequency of watering while increasing the depth of watering.

• Mowing: Once the new grass reaches mowing height, you can begin to cut it regularly. 

  • Mowing keeps weeds from spreading seeds.

  • Promotes new grass to thicken.

  • A sharp blade prevents stress on tender seedlings.  

Remember, never remove more than one-third of the grass blade each time you mow.

4. Hand-pull Weeds for the First Weeks

Right after overseeding, the safest and most effective weed control method is hand-pulling weeds. This allows you to combat weeds without damaging the young grass. 

You will want to hand-pull weeds for the first few weeks and until you have mowed the grass at least two or three times. 

5. Use Seedling-Compatible Products

Once the new grass has had time to get established (after two to three mowings), you can begin to use selective herbicides that are labeled as safe for seedlings. 

Look for products labeled as:

• Post-seeding broadleaf control

• New lawns

• Seedling-safe formula

Always follow the label instructions to the “T”, and only apply it during moderate temperatures to avoid stress.

6. Apply a Pre-Emergent Later in the Season

Once the grass is fully mature, typically after six to eight weeks, you can safely apply pre-emergent products. Remember, timing is essential. Never apply pre-emergent before, during, or right after overseeding.

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7. Fertilize and Strengthen the Lawn Through Proper Care

A thick lawn is the best long-term weed prevention. After the grass has matured, do the following:

1. Apply a balanced fertilizer that works with your grass type, season, and climate.

2. Water deeply and consistently.

3. Mow regularly at the recommended height.

Healthy grass creates its own natural weed barrier, which helps reduce weeds while limiting dependence on chemicals. 

Do Overseeding Right with Local Pros from GreenPal

If you have read this article and feel overwhelmed, there is no better way to get the lawn of your dreams than choosing to hire a Local Pro on GreenPal. 

Local Pros operating on GreenPal use region-specific fertilization and mowing schedules to keep young overseeded lawns dense and resilient throughout the entire growing season.

Hiring a Local Pro to help with overseeding your lawn is simple. Here is how it works:

1. Get Quotes: Create an account, enter your basic info, and start checking out Local Pros and getting quotes.

2. Compare Local Pros: After checking out some Local Pros and their quotes, review photos of their past work, and select who you want to work with.

3. Only Pay After: Pay only after the job is completed as promised and you are 100% satisfied. 

No contracts, no hidden fees, no games. Just quality service from Local Pros in your area!

FAQs

Should I use weed killer right after overseeding?

No. Most weed killers will harm or kill new seedlings. You will need to wait until the new grass has been mowed at least two or three times.

Why do weeds appear after overseeding?

Overseeding exposes the soil and creates conditions for dormant weed seeds to germinate. Weeds appearing after overseeding are normal and expected. 

When is a good time to apply pre-emergent?

You should apply pre-emergent later in the season, typically six to eight weeks after overseeding.

Can you mow to control weeds during germination?

Yes. Regular mowing prevents weeds from spreading their seeds and helps to thicken the new grass. 

Is it good to hand-pull weeds during early growth?

Yes. For the first few weeks after overseeding, hand-pulling weeds is the safest and most effective method.

How can I prevent weeds from coming back next season?

If you maintain a consistent mowing schedule, water properly, fertilize seasonally, and once the time is right, apply a prep-emergent, you will have done everything required to prevent weeds from coming back next season. 

Will weeds harm the new grass?

A small amount of weeds will not damage your new lawn; however, weeds left to multiply will. You should be hand-pulling weeds in the first few weeks for gradual weed control while the new grass is becoming established.