Grass Seed or Fertilizer First?

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Proper seeding and fertilizing leads to a healthy lawn.
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Seeding a lawn is a precise business and requires careful preparation to encourage proper seed germination and growth. Most grass seeds require a starter fertilizer to boost initial growth, but the application must be done carefully because the seeds will easily suffer from too much or too little fertilizer.

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When seeding grass, the order in which you add the fertilizer and seeds doesn't matter, but adding fertilizer at the time you seed a lawn is important. You can combine the fertilizer and seed and broadcast them together, or you can broadcast the seed and fertilizer separately, one immediately following the other.

Initial Fertilizer Application

When you start your lawn, spread a starter fertilizer over the ground with your grass seed. You can broadcast the seed and fertilizer separately, one immediately following the next, and it does not matter which order you spread it in. You can also place both fertilizer and seed into the same broadcast fertilizer and spread, but you must be careful to ensure that the two are thoroughly mixed, or else you will end up with an unequal distribution of seed and food.

Fertilizing After Seeding

The initial fertilizer will feed the grass seeds as they begin to germinate, but because you have to keep grass seed consistently moist during this early growth period, the food will wash out of the soil relatively quickly.

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For this reason, you should apply a second round of balanced grass fertilizer or starter fertilizer four weeks after seeding. This application will continue to boost seed germination and growth. Be sure to follow all specific product instructions regarding the amount of fertilizer to apply for your type of grass and the area you need to cover.

Best Time to Seed

The best time to sow grass seeds is in early fall. The majority of the summer heat is passed, but the soil is still warm enough to support germinating seeds. For most parts of the country, this time period can fall between late August and early October.

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As long as you plant by early October, the seed should still have time to establish itself into mature grass before the harsh winter cold sets in. If the seed has not had time to establish, the frost may kill it. You can also seed in spring, but you have to squeeze it in after the final frost date, but early enough to give the seed enough time to mature before the intensive summer heat dries it out.

Weed-and-Feed Products

Weed-and-feed products, which combine fertilizer and herbicide designed to kill weeds while promoting grass growth, should never be applied immediately before or after seeding.

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The herbicides in the weed and feed will kill young seeds and will slow or prevent germination if applied immediately following seeding. If you apply weed and feed to the lawn before you seed, wait at least six weeks to apply seed. If you want to use it after the grass is seeded, wait until you have mowed your lawn four times, which will generally occur within six to eight weeks after seeding.

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Samantha Volz

Samantha Volz has been involved in journalistic and informative writing for over eight years. She holds a bachelor's degree in English literature from Lycoming College, Williamsport, Pennsylvania, with a minor in European history. In college she was editor-in-chief of the student newspaper and completed a professional internship with the "Williamsport Sun-Gazette," serving as a full-time reporter. She resides in Horsham, Pennsylvania.