Grass seed on a lawn with crabgrass

Hello all Zone 5 - Rhode Island - not coastal.
This spring, I replanted my front lawn (3000 sq ft). I realize the spring is not the best time to plant, but I had to do it. I top-dressed with a loam-compost mix. I didn't use Tupersan when planting. Now, in some sections of the lawn, there are large clumps of crabgrass. There is too much to kill it with a crabgrass killer. I would like to over-seed the front lawn again this fall with a high-quality seed. What do I do with the crabgrass? Should I just kill it will Round-up and start over, or can I just use the slit-seeder, basically cutting through the crabgrass.
Thanks for your time.
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Killing it would seem to be an extreme solution, unless there are more weeds and undesirable grass than there is new grass. If most of it is good and salvagable except for the crabgrass, I would not start all over. In the Fall you have a window starting from maybe last week of summer and extending out about six weeks. Normally, I'd do the seeding as early in the period as practical, factoring in weather. However, with the crabgrass, I'd push it out until later in the window when the crabgrass will be done growing and declining. Probably late Sept in your area. You still have a couple months for the new grass to grow.
Cut it short and when you go over it with the slit seeder it will tear it up enough that it won't recover and be a factor. Here in coastal NJ I've seeded as late as first half of Oct with excellent results.
For future reference, the crabgrass should have been addressed when the plants were still small and relatively easy to kill.
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wrote:

Killing it would seem to be an extreme solution, unless there are more weeds and undesirable grass than there is new grass. If most of it is good and salvagable except for the crabgrass, I would not start all over. In the Fall you have a window starting from maybe last week of summer and extending out about six weeks. Normally, I'd do the seeding as early in the period as practical, factoring in weather. However, with the crabgrass, I'd push it out until later in the window when the crabgrass will be done growing and declining. Probably late Sept in your area. You still have a couple months for the new grass to grow.
Cut it short and when you go over it with the slit seeder it will tear it up enough that it won't recover and be a factor. Here in coastal NJ I've seeded as late as first half of Oct with excellent results.
For future reference, the crabgrass should have been addressed when the plants were still small and relatively easy to kill. -------------------------------------------------------------------------------- If that crabgrass has gone to seed you're screwed. If you can kill it before it does go to seed, do so and don't worry about collateral damage.
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Why exactly would he be screwed? He can simply put down a pre- emergent in Spring.

So he shouldn't worry about what effect anything he uses to kill the mature crabgrass will have on either the existing grass or his ability to re-seed now?
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wrote:

--------------------------------------------------------------------------------
Why exactly would he be screwed? He can simply put down a pre- emergent in Spring.

So he shouldn't worry about what effect anything he uses to kill the mature crabgrass will have on either the existing grass or his ability to re-seed now? ---------------------------------------------------------- You're not speaking from experience here, are you?
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Crabgrass will die in the winter but it has done it's damage by leaving seeds for the next generation. You should address this in the spring with a premerg. Make sure you get it down early which for me has always been before Forsythias bloom. Slit seeding now seems like a good idea.
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