Most types of grass seeds grow best if seeded in the yard during the early fall, between the middle of August and the middle of September. The cold weather helps preserve the seeds over the winter and allows them to take root before winter starts, and begin growing again when the temperatures rise and the soil becomes moist. The lower temperatures in late summer and early fall prevent the seeds from becoming scorched and dying.
Some types of grass seeds, including grasses that grow best in warm temperatures like Bermuda grass, should be planted in the spring, between late May and early June. Grasses that require warm temperatures to grow are unable to survive cold winter temperatures and grow best in the warmer months of the year. Types of grass that grow from plugs should also be planted in the spring so that the plugs and holes in soil are not damaged by freezing temperatures.
The condition of the soil also plays a role in whether grass seeds will successfully germinate once planted. Soil pH--whether the soil is alkaline or acidic--affects the health of grass seeds. Most grasses prefer a pH above 6.0 for the healthiest growth. Adding chemicals like lime to the soil helps prepare the pH for planting grass. Testing and, if necessary, adjusting the pH of the soil before planting grass seeds is key.
Check the weather conditions before planting grass seeds. Inclement weather around the time of planting puts seeds at risk. Heavy rains can wash away or drown seeds, while excess heat and sun will scorch the seeds and prevent them from germinating. Although fall and spring months are the best for planting grass seeds, choosing the right time to plant seeds within those months is equally important. Make sure the weather conditions are right before planting.