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. For best results, only apply fertilizer according to soil-test recommendations.
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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 nutrition will wash out of the soil relatively quickly.
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 many types of grass seeds is in early fall. The majority of the summer heat is past, 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.
As long as you sow by late September, 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.
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.