New grass won't grow where fresh herbicide exists. Using a pre-emergent weed killer on your grass helps keep pesky weeds from marring the lush, even look of your lawn. Whether you use granule or spray types, don't plant grass seed for several weeks after applying the herbicide.fter you seed, wait until you've mowed the new grass at least four times, which could be six to eight weeks after seeding, before adding herbicides. This keeps the chemicals from stunting the seedling's growth.
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Although you can't spread grass seed at the same time you spray your lawn with Weed B Gon, other options exist to treat your lawn for weeds at the same time you plant seed. These typically come in the form of weed and feed products that offer fertilizer along with the herbicide.ith the Weed B Gone Plus Crabgrass Control, wait at least four weeks to plant seed. Because this is specially formulated to stop grassy weed seeds from germinating, it also can stop your regular grass seed from growing.
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Waiting to Plant Seed. When you spread an herbicide over your lawn and then decide to patch bare spots, overseed or change your grass type to grow a new species from seed, you should wait at least a month with most pre-emergent weed killers.fter you seed, wait until you've mowed the new grass at least four times, which could be six to eight weeks after seeding, before adding herbicides. This keeps the chemicals from stunting the seedling's growth.
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Applying Pre Emergent weed killer to a lawn is a common Spring chore. Unfortunately this occurs in the same time frame when we also want to over-seed thin lawn areas, and plant new grass seed in bare areas, or lay down new grass sod.NSWER: A Pre Emergent weed killer can be an important weapon in your arsenal to fight weeds, especially the persistent problem of crabgrass. However, your question points out how important it is to get the right tool for the right job.
http://www.garden-counselor-lawn-care.com/pre-emergent.html
When you've already planted your grass seed and want to apply a pre-emergent herbicide to keep weeds from competing with your new grass for water and nutrients, have a little patience. Applying a weed-control product such as Weed B Gon too soon can kill young grass.ith the Weed B Gone Plus Crabgrass Control, wait at least four weeks to plant seed. Because this is specially formulated to stop grassy weed seeds from germinating, it also can stop your regular grass seed from growing.
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With Crabgrass Preventer. When fighting grassy weeds, you must wait a little longer to plant your grass seed, whether you're seeding your entire lawn, overseeding or treating bare patches. With the Weed B Gone Plus Crabgrass Control, wait at least four weeks to plant seed.Because this is specially formulated to stop grassy weed seeds from germinating, it also can stop your regular grass seed from growing.ith the Weed B Gone Plus Crabgrass Control, wait at least four weeks to plant seed. Because this is specially formulated to stop grassy weed seeds from germinating, it also can stop your regular grass seed from growing.
http://homeguides.sfgate.com/long-after-using-weed-b-gon-can-plant-grass-seed-87639.html
If you used a crabgrass preventer, that time frame might extend to four months. Check the herbicide manufacturer's label to confirm how long you must wait, as it can differ between herbicide products. The pre-emergent herbicides stop weed seeds from germinating, but they can stop grass seeds as well.fter you seed, wait until you've mowed the new grass at least four times, which could be six to eight weeks after seeding, before adding herbicides. This keeps the chemicals from stunting the seedling's growth.
http://homeguides.sfgate.com/long-after-using-weed-killer-can-sow-seed-83326.html
Faster Options. When you're looking for a way to kill crabgrass that doesn't include fertilizer in the mix, you can spread crabgrass preventers with siduron as the active ingredient at the same time as the seed. Mix 1 1/2 to 4 1/2 ounces of siduron with 1 gallon of water in a garden sprayer to treat 1,000 square feet.rabgrass killer doesn't always differentiate between a germinating crabgrass (Digitaria spp.) seed and a lawn grass seed.
http://www.ehow.com/facts_7707960_can-seed-after-crabgrass-killer.html
Application. The proper time to apply weed and feed to your grass is after you are able to mow the grass at least four times. In general, the first mowing of new grass takes place two to three weeks after planting and proceeds every week to two weeks after that.pplication. The proper time to apply weed and feed to your grass is after you are able to mow the grass at least four times. In general, the first mowing of new grass takes place two to three weeks after planting and proceeds every week to two weeks after that.
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After you seed, wait until you've mowed the new grass at least four times, which could be six to eight weeks after seeding, before adding herbicides.This keeps the chemicals from stunting the seedling's growth.fter you seed, wait until you've mowed the new grass at least four times, which could be six to eight weeks after seeding, before adding herbicides. This keeps the chemicals from stunting the seedling's growth.
http://homeguides.sfgate.com/long-after-using-weed-killer-can-sow-seed-83326.html
how long after putting down weed killer can i seed
You can seed six to eight weeks long after putting down weed killer.  You can seed after six to eight weeks of putting down weed killer.