Weed Killer and Grass Seeds


Old 09-29-11, 05:55 PM
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Join Date: Apr 2011
Location: USA
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Weed Killer and Grass Seeds

I just used a weed killer (a few days ago) that suggests not sowing seeds for 4 weeks after using. I figure what wasn't absorbed by the weeds has since absorbed/washed relatively deep into the soil. We've had a considerable amount of rain over the last couple of days. I was going to wait for a full week then go ahead and sow grass seeds. I need to get the seeds in/on the ground ASAP. If I wait 4 weeks, I'm going to miss the most productive growth. Do I really need to wait 4 weeks? Any thoughts? The seeds will only be slightly below the surface. Why wouldn't that work?

FYI This is my second use of the product. The product is Green Light Wipe-Out Crabgrass Killer Plus Concentrate. It worked VERY well with the first treatment. I had a few stragglers and wanted to be sure I knocked them all out (reason for second treatment). Unlike other products I've used in the past, this stuff really killed the crabgrass.
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Old 09-30-11, 11:58 PM
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if it is strickly a post emergant product like round-up you should be ok to seed but if it has a pre-emergant component then you may have problems with the seeds taking root.
Old 10-01-11, 06:34 AM
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When the label says you should leave the grass clippings on the lawn for the next 3 clippings, that tells me that the product says in the soil active for at least 3 weeks. I think if you seed too soon very little of your seed will sprout and you will be buying grass seed again in 3 weeks. If you don't mind buying more seed then go ahead. But I wouldn't expect it to sprout. Been there done that.
Old 10-01-11, 03:40 PM
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Join Date: Apr 2011
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Didn't think of that (post emergant). Here's part of the product information...

"NEW Wipe-Out Crabgrass Killer PLUS Concentrate is a selective herbicide that kills crabgrass plus over 250 other emerged broadleaf and listed grass weeds in established lawns.".

It doesn't sound like a pre-emergent product. Like XSleeper said, I can try sowing the seeds and see if they sprout, if they don't, I'll seed again. Maybe I'll wait 2 weeks and give it a shot. Thanks for the responses.
Old 10-05-11, 08:44 AM
Join Date: Dec 2005
Location: USA
Posts: 3,188
William - Can I ask why you are using an emergent weed killer at this time of the year? Crabgrass is going to die shortly and the thing you should be most concerned about should be the pre emergent seeds that this years crabgrass crop has left behind.

I don't know what part of the country you are in so I may be off base here, but I know in the Northeast killing existing crabgrass in the fall is kind of a waste of time.

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