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overseeding after pre-emergent has been sprayed?


LawnSite Member
Hi, I'm in need of some info from someone who has experience with herbicides. I have a customer whom I was planning on overseeding their lawn in the next couple days, and thought just to be sure I'd make sure their lawn hasn't been sprayed with any kind of pre-emergent because I have read everywhere that grass seed will not germinate if a pre emerg has been applied, and you must wait anywhere from 6 weeks to 3-4 months before or after it is applied. So of course we found out it had been sprayed with a pre-emergent crabgrass control and I discussed my concern with the customer, she called the weed company and they told her that if you were to put down the seed before the pre-emerg was applied than you have to wait 6 weeks but since the pre emerg was already applied(3 days ago) you only have to wait one week to plant seed. I don't know too much about herbicides but everything I read goes against what this weed company has said. I would sincerely appreciate any info or advice from someone with the knowledge to clarify this for me. Thanks.


LawnSite Senior Member
Albuquerque NM
The pre-emergant will interfere with the seeds germination for several weeks til 3-4 months depending on the preemerge they used whether seeded before or after they sprayed.


LawnSite Bronze Member
Gambrills, MD
If you're going to seed it, drag harrow it after a heavy rain, and this will break the herbicide film, allowing at least some of the seed to germinate. It will also allow crabgrass to germinate, so advise against seeding till fall, which is the best time, anyway.


LawnSite Senior Member
Oly Wa
You are farther north and on the other side of the continent than me so I can only try to help. You may only have to wait for the low end of the time scale I think. I would think it would still be on the early side of overseeding season where you are, but I'm not sure. Then again it should also be early for pre-em? I don't know your climate. The rain leaches a lot away. Anyway I would bet that if you overseeded to the end of your spring rainy season you would make out ok. Also find out just what was used, they have to tell you and you can look up all the info you need to decide what to do.


LawnSite Fanatic
Clinton, NJ
Don't even bother.

Even if you aerate and seed, you will get lousy results (if any). This exact situation happened to me a few years back not knowing a fert company used a pre-m a week before I aerated and seeded. Wait until the Fall IMO.


LawnSite Bronze Member
You can use Tupersan (siduron) as a pre-emergant and seed through it. Big $$ for a bag, but it's the only gae in town. Hydro seeders are mixing Drive into thier mix at a 1/2lb per acre. There is supplemental labeling for that too.