When you sow grass seed into your lawn, the time of year is one of the biggest factors in the grass's potential success or failure. Certain yearly conditions give the grass the greatest chance of success, while other conditions make it almost impossible to bring the seed to sprout.
Considerations for Sowing Grass Seed
While you can work grass seed into your lawn at any time, for much of the year this will simply be a waste of grass seed. Grass seed requires certain soil and air temperatures to grow, as well as the correct placement in the soil. Once all those factors are good, the grass still needs little competition from other plants for nutrients and ample moisture.
The Best Time to Sow Grass Seed
While the exact time may vary based on your particular climate, the best time to sow grass is in either late August or early September. During this time, the temperatures are coming down off of their summer highs when many cool-season grasses stop growing. As the nights are growing longer, less moisture is evaporated out of the soil, so the new grass requires less supplemental moisture from watering. Finally, most weed seeds do not grow during the fall, meaning your grass will have almost no competition for soil nutrients.
Alternate Sowing Times
After fall, the next best time to sow grass seed is in the early spring. Put the seed into the ground in March or April, once the snow is gone and the ground has thawed. As you fertilise and water the grass seed, you will be fertilising and watering the weeds as well, so be ready to pull a lot of weeds from your new lawn. The middle of summer is another option for planting grass seed, but it's not really a good one. The new grass will require almost constant watering to overcome the amount of evaporation in the summer. Finally, if you just can't wait, you can apply seed in the late fall and let it sit dormant all winter. If the seed doesn't get washed away or eaten, it will start to sprout when the temperature rises in the early spring.
The Sowing Process
Sowing grass seed at the right time won't help if you are sowing the seed in the wrong manner. Spread the seed evenly into loose soil and rake the seed just under the top of the soil. Add a covering, like mulch, if you are sowing in hot or cold weather, or if you are sowing on a hillside. Add a starter fertiliser to the area, and then water vigorously until the grass starts to sprout.