There are many possible reasons why the grass seed you planted did not germinate properly. In order to grow healthy and lush grass, the temperature, soil conditions and moisture must remain within acceptable ranges. Typically, grass will begin to germinate within two to three weeks after being planted. If you have not seen any germination shortly after this recommended germination period, you will want to examine your growing area, as well as the grass seed used, for possible reasons.
Check for proper aeration. Hard, crusted soil with no air circulation is not conducive to grass germination. Aerate existing lawn that have been over seeded with new grass seed or use a rake to lightly break up the top 4 inches of soil on newly seeded areas.
Verify you used enough grass seed per square foot. Sowing too few grass seeds per square foot will result in poor seed germination. Consult the seed bag for proper sowing ratios and reseed with the correct amount if necessary.
Check the age of the grass seed used. The date on the seed bag should be no farther backdated than nine months from the date you planted the grass seed. Reseed with new grass seed, if the seed used is expired and there is time before the first frost arrives.
Keep the soil moist. Grass seed will only germinate in moist soil conditions.
Add a phosphate-rich fertilizer. If fertilizer was not used prior to planting your grass seed, add it now at a rate of 8 lbs. per 1,000 square feet. A 6-12-12 fertilizer is recommended.